Editorial

133 KiB

Open AccessEditorial

by Minhua Shao

Catalysts 2015, 5(4), 2115-2121; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5042115 - 09 Dec 2015

Cited by 22 | Viewed by 5516

Low temperature fuel cells are expected to come into widespread commercial use in the areas of transportation and stationary and portable power generation, and thus will help solve energy shortage and environmental issues. [...] Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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Research

Jump to: Editorial, Review

1035 KiB

Open AccessFeature PaperArticle

Application of a Coated Film Catalyst Layer Model to a High Temperature Polymer Electrolyte Membrane Fuel Cell with Low Catalyst Loading Produced by Reactive Spray Deposition Technology

by Timothy D. Myles, Siwon Kim, Radenka Maric and William E. Mustain

Catalysts 2015, 5(4), 1673-1691; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5041673 - 10 Oct 2015

Cited by 12 | Viewed by 7400

Abstract

In this study, a semi-empirical model is presented that correlates to previously obtained experimental overpotential data for a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). The goal is to reinforce the understanding of the performance of the cell from a modeling perspective. [...] Read more.

In this study, a semi-empirical model is presented that correlates to previously obtained experimental overpotential data for a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). The goal is to reinforce the understanding of the performance of the cell from a modeling perspective. The HT-PEMFC membrane electrode assemblies (MEAs) were constructed utilizing an 85 wt. % phosphoric acid doped Advent TPS® membranes for the electrolyte and gas diffusion electrodes (GDEs) manufactured by Reactive Spray Deposition Technology (RSDT). MEAs with varying ratios of PTFE binder to carbon support material (I/C ratio) were manufactured and their performance at various operating temperatures was recorded. The semi-empirical model derivation was based on the coated film catalyst layer approach and was calibrated to the experimental data by a least squares method. The behavior of important physical parameters as a function of I/C ratio and operating temperature were explored. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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685 KiB

Open AccessArticle

Copolymers Based on Indole-6-Carboxylic Acid and 3,4-Ethylenedioxythiophene as Platinum Catalyst Support for Methanol Oxidation

by Tzi-Yi Wu, Chung-Wen Kuo, Yu-Lun Chen and Jeng-Kuei Chang

Catalysts 2015, 5(4), 1657-1672; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5041657 - 05 Oct 2015

Cited by 10 | Viewed by 5457

Abstract

Indole-6-carboxylic acid (ICA) and 3,4-ethylenedioxythiophene (EDOT) are copolymerized electrochemically on a stainless steel (SS) electrode to obtain poly(indole-6-carboxylic acid-co-3,4-ethylenedioxythiophene)s (P(ICA-co-EDOT))s. The morphology of P(ICA-co-EDOT)s is checked using scanning electron microscopy (SEM), and the SEM images reveal that [...] Read more.

Indole-6-carboxylic acid (ICA) and 3,4-ethylenedioxythiophene (EDOT) are copolymerized electrochemically on a stainless steel (SS) electrode to obtain poly(indole-6-carboxylic acid-co-3,4-ethylenedioxythiophene)s (P(ICA-co-EDOT))s. The morphology of P(ICA-co-EDOT)s is checked using scanning electron microscopy (SEM), and the SEM images reveal that these films are composed of highly porous fibers when the feed molar ratio of ICA/EDOT is greater than 3/2. Platinum particles can be electrochemically deposited into the P(ICA-co-EDOT)s and PICA films to obtain P(ICA-co-EDOT)s-Pt and PICA-Pt composite electrodes, respectively. These composite electrodes are further characterized using X-ray photoelectron spectroscopy (XPS), SEM, X-ray diffraction analysis (XRD), and cyclic voltammetry (CV). The SEM result indicates that Pt particles disperse more uniformly into the highly porous P(ICA3-co-EDOT2) fibers (feed molar ratio of ICA/EDOT = 3/2). The P(ICA3-co-EDOT2)-Pt nanocomposite electrode exhibited excellent catalytic activity for the electrooxidation of methanol in these electrodes, which reveals that P(ICA3-co-EDOT2)-Pt nanocomposite electrodes are more promising for application in an electrocatalyst as a support material. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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1270 KiB

Open AccessArticle

Electrocatalytic Activity and Durability of Pt-Decorated Non-Covalently Functionalized Graphitic Structures

by Emanuela Negro, Alessandro Stassi, Vincenzo Baglio, Antonino S. Aricò and Ger J.M. Koper

Catalysts 2015, 5(3), 1622-1635; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031622 - 21 Sep 2015

Cited by 10 | Viewed by 5401

Abstract

Carbon graphitic structures that differ in morphology, graphiticity and specific surface area were used as support for platinum for Oxygen Reduction Reaction (ORR) in low temperature fuel cells. Graphitic supports were first non-covalently functionalized with pyrene carboxylic acid (PCA) and, subsequently, platinum nanoparticles [...] Read more.

Carbon graphitic structures that differ in morphology, graphiticity and specific surface area were used as support for platinum for Oxygen Reduction Reaction (ORR) in low temperature fuel cells. Graphitic supports were first non-covalently functionalized with pyrene carboxylic acid (PCA) and, subsequently, platinum nanoparticles were nucleated on the surface following procedures found in previous studies. Non-covalent functionalization has been proven to be advantageous because it allows for a better control of particle size and monodispersity, it prevents particle agglomeration since particles are bonded to the surface, and it does not affect the chemical and physical resistance of the support. Synthesized electrocatalysts were characterized by electrochemical half-cell studies, in order to evaluate the Electrochemically Active Surface Area (ECSA), ORR activity, and durability to potential cycling and corrosion resistance. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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1318 KiB

Open AccessArticle

The Use of C-MnO₂ as Hybrid Precursor Support for a Pt/C-Mn_xO_1+x Catalyst with Enhanced Activity for the Methanol Oxidation Reaction (MOR)

by Alessandro H.A. Monteverde Videla, Luigi Osmieri, Reza Alipour Moghadam Esfahani, Juqin Zeng, Carlotta Francia and Stefania Specchia

Catalysts 2015, 5(3), 1399-1416; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031399 - 30 Jul 2015

Cited by 23 | Viewed by 10000

Abstract

Platinum (Pt) nanoparticles are deposited on a hybrid support (C-MnO₂) according to a polyol method. The home-made catalyst, resulted as Pt/C-Mn_xO_1+x, is compared with two different commercial platinum based materials (Pt/C and PtRu/C). The synthesized catalyst [...] Read more.

Platinum (Pt) nanoparticles are deposited on a hybrid support (C-MnO₂) according to a polyol method. The home-made catalyst, resulted as Pt/C-Mn_xO_1+x, is compared with two different commercial platinum based materials (Pt/C and PtRu/C). The synthesized catalyst is characterized by means of FESEM, XRD, ICP-MS, XPS and μRS analyses. MnO₂ is synthesized and deposited over a commercial grade of carbon (Vulcan XC72) by facile reduction of potassium permanganate in acidic solution. Pt nanoparticles are synthesized on the hybrid support by a polyol thermal assisted method (microwave irradiation), followed by an annealing at 600 °C. The obtained catalyst displays a support constituted by a mixture of manganese oxides (Mn₂O₃ and Mn₃O₄) with a Pt loading of 19 wt. %. The electro-catalytic activity towards MOR is assessed by RDE in acid conditions (0.5 M H₂SO₄), evaluating the ability to oxidize methanol in 1 M concentration. The synthesized Pt/C-Mn_xO_1+x catalyst shows good activity as well as good stability compared to the commercial Pt/C based catalyst. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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449 KiB

Open AccessArticle

Sb Surface Modification of Pd by Mimetic Underpotential Deposition for Formic Acid Oxidation

by Long-Long Wang, Xiao-Lu Cao, Ya-Jun Wang and Qiao-Xia Li

Catalysts 2015, 5(3), 1388-1398; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031388 - 28 Jul 2015

Cited by 7 | Viewed by 5908

Abstract

The newly proposed mimetic underpotential deposition (MUPD) technique was extended to modify Pd surfaces with Sb through immersing a Pd film electrode or dispersing Pd/C powder in a Sb(III)-containing solution blended with ascorbic acid (AA). The introduction of AA shifts down the open [...] Read more.

The newly proposed mimetic underpotential deposition (MUPD) technique was extended to modify Pd surfaces with Sb through immersing a Pd film electrode or dispersing Pd/C powder in a Sb(III)-containing solution blended with ascorbic acid (AA). The introduction of AA shifts down the open circuit potential of Pd substrate available to achieve suitable Sb modification. The electrocatalytic activity and long-term stability towards HCOOH electrooxidation of the Sb modified Pd surfaces (film electrode or powder catalyst) by MUPD is superior than that of unmodified Pd and Sb modified Pd surfaces by conventional UPD method. The enhancement of electrocatalytic performance is due to the third body effect and electronic effect, as well as bi-functional mechanism induced by Sb modification which result in increased resistance against CO poisoning. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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1689 KiB

Open AccessArticle

Simple Preparation of Pd Core Nanoparticles for Pd Core/Pt Shell Catalyst and Evaluation of Activity and Durability for Oxygen Reduction Reaction

by Hiroshi Inoue, Ryotaro Sakai, Taiki Kuwahara, Masanobu Chiku and Eiji Higuchi

Catalysts 2015, 5(3), 1375-1387; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031375 - 28 Jul 2015

Cited by 7 | Viewed by 7291

Abstract

Pd core nanoparticles less than 5 nm in mean size were prepared on carbon black (CB) without any stabilizer by using palladium acetate as a precursor and CO as a reducing agent, and then used for preparing Pd core/Pt shell nanoparticles-loaded CB (Pt/Pd/CB). [...] Read more.

Pd core nanoparticles less than 5 nm in mean size were prepared on carbon black (CB) without any stabilizer by using palladium acetate as a precursor and CO as a reducing agent, and then used for preparing Pd core/Pt shell nanoparticles-loaded CB (Pt/Pd/CB). The mean size of Pd nanoparticles could be controlled by the concentration of palladium acetate and the CO bubbling time. The cyclic voltammograms of two Pd nanoparticles-loaded CB (Pd_4.2/CB, Pd_3.3/CB) electrodes whose mean size was 4.2 and 3.3 nm, respectively, had characteristics similar to a Pt electrode after the formation of a Pt monolayer shell, suggesting that the Pd core nanoparticles were almost covered with the Pt monolayer shell. The oxygen reduction reaction (ORR) on both Pt/Pd/CB proceeded in 4-electron reduction mechanism. Both Pt/Pd/CB electrodes was ca. 1.5 times higher in ORR activity per electrochemical surface area of Pt (specific activity, SA) than the commercial Pt nanoparticles-loaded CB (Tanaka Kikinzoku Kogyo, Pt/CB-TKK) electrode, and the Pt/Pd_3.3/CB electrode had higher SA than the Pt/Pd_4.2/CB electrode. The ORR activity per unit mass of Pt for both Pt/Pd/CB electrodes was 5.0 and 5.5 times as high as that for the Pt/CB-TKK electrode, respectively. The durability of both Pt/Pd/CB electrodes was comparable to that of Pt/CB-TKK. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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2153 KiB

Open AccessArticle

Effect of ZIF-8 Crystal Size on the O₂ Electro-Reduction Performance of Pyrolyzed Fe–N–C Catalysts

by Vanessa Armel, Julien Hannauer and Frédéric Jaouen

Catalysts 2015, 5(3), 1333-1351; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031333 - 24 Jul 2015

Cited by 42 | Viewed by 12378

Abstract

The effect of ZIF-8 crystal size on the morphology and performance of Fe–N–C catalysts synthesized via the pyrolysis of a ferrous salt, phenanthroline and the metal-organic framework ZIF-8 is investigated in detail. Various ZIF-8 samples with average crystal size ranging from 100 to [...] Read more.

The effect of ZIF-8 crystal size on the morphology and performance of Fe–N–C catalysts synthesized via the pyrolysis of a ferrous salt, phenanthroline and the metal-organic framework ZIF-8 is investigated in detail. Various ZIF-8 samples with average crystal size ranging from 100 to 1600 nm were prepared. The process parameters allowing a templating effect after argon pyrolysis were investigated. It is shown that the milling speed, used to prepare catalyst precursors, and the heating mode, used for pyrolysis, are critical factors for templating nano-ZIFs into nano-sized Fe–N–C particles with open porosity. Templating could be achieved when combining a reduced milling speed with a ramped heating mode. For templated Fe–N–C materials, the performance and activity improved with decreased ZIF-8 crystal size. With the Fe–N–C catalyst templated from the smallest ZIF-8 crystals, the current densities in H₂/O₂ polymer electrolyte fuel cell at 0.5 V reached ca. 900 mA cm⁻², compared to only ca. 450 mA cm⁻² with our previous approach. This templating process opens the path to a morphological control of Fe–N–C catalysts derived from metal-organic frameworks which, when combined with the versatility of the coordination chemistry of such materials, offers a platform for the rational design of optimized Metal–N–C catalysts. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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6339 KiB

Open AccessArticle

Pt Monolayer Shell on Nitrided Alloy Core—A Path to Highly Stable Oxygen Reduction Catalyst

by Jue Hu, Kurian A. Kuttiyiel, Kotaro Sasaki, Dong Su, Tae-Hyun Yang, Gu-Gon Park, Chengxu Zhang, Guangyu Chen and Radoslav R. Adzic

Catalysts 2015, 5(3), 1321-1332; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031321 - 22 Jul 2015

Cited by 28 | Viewed by 7732

Abstract

The inadequate activity and stability of Pt as a cathode catalyst under the severe operation conditions are the critical problems facing the application of the proton exchange membrane fuel cell (PEMFC). Here we report on a novel route to synthesize highly active and [...] Read more.

The inadequate activity and stability of Pt as a cathode catalyst under the severe operation conditions are the critical problems facing the application of the proton exchange membrane fuel cell (PEMFC). Here we report on a novel route to synthesize highly active and stable oxygen reduction catalysts by depositing Pt monolayer on a nitrided alloy core. The prepared Pt_MLPdNiN/C catalyst retains 89% of the initial electrochemical surface area after 50,000 cycles between potentials 0.6 and 1.0 V. By correlating electron energy-loss spectroscopy and X-ray absorption spectroscopy analyses with electrochemical measurements, we found that the significant improvement of stability of the Pt_MLPdNiN/C catalyst is caused by nitrogen doping while reducing the total precious metal loading. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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8126 KiB

Open AccessArticle

Titanium-Niobium Oxides as Non-Noble Metal Cathodes for Polymer Electrolyte Fuel Cells

by Akimitsu Ishihara, Yuko Tamura, Mitsuharu Chisaka, Yoshiro Ohgi, Yuji Kohno, Koichi Matsuzawa, Shigenori Mitsushima and Ken-ichiro Ota

Catalysts 2015, 5(3), 1289-1303; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031289 - 17 Jul 2015

Cited by 21 | Viewed by 7844

Abstract

In order to develop noble-metal- and carbon-free cathodes, titanium-niobium oxides were prepared as active materials for oxide-based cathodes and the factors affecting the oxygen reduction reaction (ORR) activity were evaluated. The high concentration sol-gel method was employed to prepare the precursor. Heat treatment [...] Read more.

In order to develop noble-metal- and carbon-free cathodes, titanium-niobium oxides were prepared as active materials for oxide-based cathodes and the factors affecting the oxygen reduction reaction (ORR) activity were evaluated. The high concentration sol-gel method was employed to prepare the precursor. Heat treatment in Ar containing 4% H₂ at 700–900 °C was effective for conferring ORR activity to the oxide. Notably, the onset potential for the ORR of the catalyst prepared at 700 °C was approximately 1.0 V vs. RHE, resulting in high quality active sites for the ORR. X-ray (diffraction and photoelectron spectroscopic) analyses and ionization potential measurements suggested that localized electronic energy levels were produced via heat treatment under reductive atmosphere. Adsorption of oxygen molecules on the oxide may be governed by the localized electronic energy levels produced by the valence changes induced by substitutional metal ions and/or oxygen vacancies. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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1389 KiB

Open AccessArticle

Facile Electrodeposition of Flower-Like PMo₁₂-Pt/rGO Composite with Enhanced Electrocatalytic Activity towards Methanol Oxidation

by Xiaoying Wang, Xiaofeng Zhang, Xiaolei He, Ai Ma, Lijuan Le and Shen Lin

Catalysts 2015, 5(3), 1275-1288; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031275 - 17 Jul 2015

Cited by 11 | Viewed by 6944

Abstract

A facile, rapid and green method based on potentiostatic electrodeposition is developed to synthesize a novel H₃PMo₁₂O₄₀-Pt/reduced graphene oxide (denoted as PMo₁₂-Pt/rGO) composite. The as-prepared PMo₁₂-Pt/rGO is characterized by X-ray diffraction (XRD), scanning [...] Read more.

A facile, rapid and green method based on potentiostatic electrodeposition is developed to synthesize a novel H₃PMo₁₂O₄₀-Pt/reduced graphene oxide (denoted as PMo₁₂-Pt/rGO) composite. The as-prepared PMo₁₂-Pt/rGO is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results reveal that graphene oxide (GO) is reduced to the rGO by electrochemical method and POMs clusters are successfully located on the rGO as the modifier. Furthermore, the PMo₁₂-Pt/rGO composite shows higher electrocatalytic activity, better tolerance towards CO and better stability than the conventional pure Pt catalyst. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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10130 KiB

Open AccessArticle

Positive Effect of Heat Treatment on Carbon-Supported CoS Nanocatalysts for Oxygen Reduction Reaction

by Haihong Zhong, Jingmin Xi, Pinggui Tang, Dianqing Li and Yongjun Feng

Catalysts 2015, 5(3), 1211-1220; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031211 - 15 Jul 2015

Cited by 10 | Viewed by 5818

Abstract

It is of increasing interest and an important challenge to develop highly efficient less-expensive cathode catalysts for anion-exchange membrane fuel cells (AEMFCs). In this work, we have directly prepared a carbon-supported CoS nanocatalyst in a solvothermal route and investigated the effect of heat-treatment [...] Read more.

It is of increasing interest and an important challenge to develop highly efficient less-expensive cathode catalysts for anion-exchange membrane fuel cells (AEMFCs). In this work, we have directly prepared a carbon-supported CoS nanocatalyst in a solvothermal route and investigated the effect of heat-treatment on electrocatalytic activity and long-term stability using rotating ring-disk electrode (RRDE). The results show that the heat-treatment below 400 °C under nitrogen atmosphere significantly enhanced the electrocatalytic performance of CoS catalyst as a function of annealed temperature in terms of the cathodic current density, the half-wave potential, the HO₂⁻ product and the number of electrons transferred. The CoS catalyst that annealed at 400 °C (CoS-400) has exhibited a promising performance with the half-wave potential of 0.71 V vs. RHE (the highest one for non-precious metal chalcogenides), the minimum HO₂⁻ product of 4.3% at 0.60 V vs. RHE and close to the 4-electron pathway during the oxygen reduction reaction in 0.1 M KOH. Also, the CoS-400 catalyst has comparable durability to the Pt/C catalyst. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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1032 KiB

Open AccessCommunication

Surfactant-Template Preparation of Polyaniline Semi-Tubes for Oxygen Reduction

by Shiming Zhang and Shengli Chen

Catalysts 2015, 5(3), 1202-1210; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031202 - 07 Jul 2015

Cited by 15 | Viewed by 6004

Abstract

Nitrogen and metal doped nanocarbons derived from polyaniline (PANI) have been widely explored as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. In this work, we report surfactant-template synthesis of PANI nanostructures and the ORR electrocatalysts derived from them. By using [...] Read more.

Nitrogen and metal doped nanocarbons derived from polyaniline (PANI) have been widely explored as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. In this work, we report surfactant-template synthesis of PANI nanostructures and the ORR electrocatalysts derived from them. By using cationic surfactant such as the cetyl trimethyl ammonium bromide (CTAB) as the template and the negatively charged persulfate ions as the oxidative agent to stimulate the aniline polymerization in the micelles of CTAB, PANI with a unique 1-D semi-tubular structure can be obtained. The semi-tubular structure can be maintained even after high-temperature treatment at 900 °C, which yields materials exhibiting promising ORR activity. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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971 KiB

Open AccessArticle

Pt Monolayer Electrocatalyst for Oxygen Reduction Reaction on Pd-Cu Alloy: First-Principles Investigation

by Amra Peles, Minhua Shao and Lesia Protsailo

Catalysts 2015, 5(3), 1193-1201; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031193 - 06 Jul 2015

Cited by 13 | Viewed by 5897

Abstract

First principles approach is used to examine geometric and electronic structure of the catalyst concept aimed to improve activity and utilization of precious Pt metal for oxygen reduction reaction in fuel cells. The Pt monolayers on Pd skin and Pd_1-xCu_x [...] Read more.

First principles approach is used to examine geometric and electronic structure of the catalyst concept aimed to improve activity and utilization of precious Pt metal for oxygen reduction reaction in fuel cells. The Pt monolayers on Pd skin and Pd_1-xCu_x inner core for various compositions x were examined by building the appropriate models starting from Pd-Cu solid solution. We provided a detailed description of changes in the descriptors of catalytic behavior, d-band energy and binding energies of reaction intermediates, giving an insight into the underlying mechanism of catalytic activity enhancement based on the first principles density functional theory (DFT) calculations. Structural properties of the Pd-Cu bimetallic were determined for bulk and surfaces, including the segregation profile of Cu under different environment on the surface. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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5988 KiB

Open AccessArticle

Microwave Synthesis of High Activity FeSe₂/C Catalyst toward Oxygen Reduction Reaction

by Qiaoling Zheng, Xuan Cheng and Hengyi Li

Catalysts 2015, 5(3), 1079-1091; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031079 - 30 Jun 2015

Cited by 62 | Viewed by 8441

Abstract

The carbon supported iron selenide catalysts (FeSe₂/C) were prepared with various selenium to iron ratios (Se/Fe), namely, Se/Fe = 2.0, 2.5, 3.0, 3.5 and 4.0, through facile microwave route by using ferrous oxalate (FeC₂O₄·2H₂O) and [...] Read more.

The carbon supported iron selenide catalysts (FeSe₂/C) were prepared with various selenium to iron ratios (Se/Fe), namely, Se/Fe = 2.0, 2.5, 3.0, 3.5 and 4.0, through facile microwave route by using ferrous oxalate (FeC₂O₄·2H₂O) and selenium dioxide (SeO₂) as precursors. Accordingly, effects of Se/Fe ratio on the crystal structure, crystallite size, microstructure, surface composition and electrocatalytic activity for oxygen reduction reaction (ORR) of FeSe₂/C in an alkaline medium were systematically investigated. The results revealed that all the FeSe₂/C catalysts obtained with the Se/Fe ratios of 2.0–4.0 exhibited almost pure orthogonal FeSe₂ structure with the estimated mean crystallite sizes of 32.9–36.2 nm. The electrocatalytic activities in potassium hydroxide solutions were higher than those in perchloric acid solutions, and two peak potentials or two plateaus responded to ORR were observed from cyclic voltammograms and polarization curves, respectively. The ORR potentials of 0.781–0.814 V with the electron transfer numbers of 3.3–3.9 at 0.3 V could be achieved as the Se/Fe ratios varied from 2.0 to 4.0. The Fe and Se were presented at the surface of FeSe₂/C upon further reduction on FeSe₂. The Se/Fe ratios slightly influenced the degree of graphitization in carbon support and the amount of active sites for ORR. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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5847 KiB

Open AccessArticle

Preparation and Electrocatalytic Characteristics of PdW/C Catalyst for Ethanol Oxidation

by Qi Liu, Mingshuang Liu, Qiaoxia Li and Qunjie Xu

Catalysts 2015, 5(3), 1068-1078; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031068 - 29 Jun 2015

Cited by 7 | Viewed by 6258

Abstract

A series of PdW alloy supported on Vulcan XC-72 Carbon (PdW/C) with total 20 wt. % as electrocatalyst are prepared for ethanol oxidation by an ethylene glycol assisted method. Transmission electron microscopy (TEM) characterization shows that PdW nanoparticles with an average size of [...] Read more.

A series of PdW alloy supported on Vulcan XC-72 Carbon (PdW/C) with total 20 wt. % as electrocatalyst are prepared for ethanol oxidation by an ethylene glycol assisted method. Transmission electron microscopy (TEM) characterization shows that PdW nanoparticles with an average size of 3.6 nm are well dispersed on the surface of Vulcan XC-72 Carbon. It is found that the catalytic activity and stability of the PdW/C catalysts are strongly dependent on Pd/W ratios, an optimal Pd/W composition at 1/1 ratio revealed the highest catalytic activity toward ethanol oxidation, which is much better than commercial Pd/C catalysts. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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12370 KiB

Open AccessArticle

Novel Mesoporous Carbon Supports for PEMFC Catalysts

by Dustin Banham, Fangxia Feng, Tobias Fürstenhaupt, Katie Pei, Siyu Ye and Viola Birss

Catalysts 2015, 5(3), 1046-1067; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031046 - 29 Jun 2015

Cited by 40 | Viewed by 7563

Abstract

Over the past decade; a significant amount of research has been performed on novel carbon supports for use in proton exchange membrane fuel cells (PEMFCs). Specifically, carbon nanotubes, ordered mesoporous carbon, and colloid imprinted carbons have shown great promise for improving the activity [...] Read more.

Over the past decade; a significant amount of research has been performed on novel carbon supports for use in proton exchange membrane fuel cells (PEMFCs). Specifically, carbon nanotubes, ordered mesoporous carbon, and colloid imprinted carbons have shown great promise for improving the activity and/or stability of Pt-based nanoparticle catalysts. In this work, a brief overview of these materials is given, followed by an in-depth discussion of our recent work highlighting the importance of carbon wall thickness when designing novel carbon supports for PEMFC applications. Four colloid imprinted carbons (CICs) were synthesized using a silica colloid imprinting method, with the resulting CICs having pores of 15 (CIC-15), 26 (CIC-26), 50 (CIC-50) and 80 (CIC-80) nm. These four CICs were loaded with 10 wt. % Pt and then evaluated as oxygen reduction (ORR) catalysts for use in proton exchange membrane fuel cells. To gain insight into the poorer performance of Pt/CIC-26 vs. the other three Pt/CICs, TEM tomography was performed, indicating that CIC-26 had much thinner walls (0–3 nm) than the other CICs and resulting in a higher resistance (leading to distributed potentials) through the catalyst layer during operation. This explanation for the poorer performance of Pt/CIC-26 was supported by theoretical calculations, suggesting that the internal wall thickness of these nanoporous CICs is critical to the future design of porous carbon supports. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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2414 KiB

Open AccessArticle

Polyaniline-Derived Ordered Mesoporous Carbon as an Efficient Electrocatalyst for Oxygen Reduction Reaction

by Kai Wan, Zhi-Peng Yu and Zhen-Xing Liang

Catalysts 2015, 5(3), 1034-1045; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031034 - 26 Jun 2015

Cited by 23 | Viewed by 6176

Abstract

Nitrogen-doped ordered mesoporous carbon was synthesized by using polyaniline as the carbon source and SBA-15 as the template. The microstructure, composition and electrochemical behavior were extensively investigated by the nitrogen sorption isotherm, X-ray photoelectron spectroscopy, cyclic voltammetry and rotating ring-disk electrode. It is [...] Read more.

Nitrogen-doped ordered mesoporous carbon was synthesized by using polyaniline as the carbon source and SBA-15 as the template. The microstructure, composition and electrochemical behavior were extensively investigated by the nitrogen sorption isotherm, X-ray photoelectron spectroscopy, cyclic voltammetry and rotating ring-disk electrode. It is found that the pyrolysis temperature yielded a considerable effect on the pore structure, elemental composition and chemical configuration. The pyrolysis temperature from 800 to 1100 °C yielded a volcano-shape relationship with both the specific surface area and the content of the nitrogen-activated carbon. Electrochemical tests showed that the electrocatalytic activity followed a similar volcano-shape relationship, and the carbon catalyst synthesized at 1000 °C yielded the best performance. The post-treatment in NH₃ was found to further increase the specific surface area and to enhance the nitrogen doping, especially the edge-type nitrogen, which favored the oxygen reduction reaction in both acid and alkaline media. The above findings shed light on electrocatalysis and offer more strategies for the controllable synthesis of the doped carbon catalyst. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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1188 KiB

Open AccessArticle

Improving the Ethanol Oxidation Activity of Pt-Mn Alloys through the Use of Additives during Deposition

by Mohammadreza Zamanzad Ghavidel and E. Bradley Easton

Catalysts 2015, 5(3), 1016-1033; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031016 - 25 Jun 2015

Cited by 12 | Viewed by 6233

Abstract

In this work, sodium citrate (SC) was used as an additive to control the particle size and dispersion of Pt-Mn alloy nanoparticles deposited on a carbon support. SC was chosen, since it was the only additive tested that did not prevent Mn from [...] Read more.

In this work, sodium citrate (SC) was used as an additive to control the particle size and dispersion of Pt-Mn alloy nanoparticles deposited on a carbon support. SC was chosen, since it was the only additive tested that did not prevent Mn from co-depositing with Pt. The influence of solution pH during deposition and post-deposition heat treatment on the physical and electrochemical properties of the Pt-Mn alloy was examined. It was determined that careful control over pH is required, since above a pH of four, metal deposition was suppressed. Below pH 4, the presence of sodium citrate reduced the particle size and improved the particle dispersion. This also resulted in larger electrochemically-active surface areas and greater activity towards the ethanol oxidation reaction (EOR). Heat treatment of catalysts prepared using the SC additive led to a significant enhancement in EOR activity, eclipsing the highest activity of our best Pt-Mn/C prepared in the absence of SC. XRD studies verified the formation of the Pt-Mn intermetallic phase upon heat treatment. Furthermore, transmission electron microscopy studies revealed that catalysts prepared using the SC additive were more resistant to particle size growth during heat treatment. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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1013 KiB

Open AccessArticle

Synthesis and Electrocatalytic Performance of Multi-Component Nanoporous PtRuCuW Alloy for Direct Methanol Fuel Cells

by Xiaoting Chen, Hao Wang, Ying Wang, Qingguo Bai, Yulai Gao and Zhonghua Zhang

Catalysts 2015, 5(3), 1003-1015; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031003 - 24 Jun 2015

Cited by 26 | Viewed by 6489

Abstract

We have prepared a multi-component nanoporous PtRuCuW (np-PtRuCuW) electrocatalyst via a combined chemical dealloying and mechanical alloying process. The X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrochemical measurements have been applied to characterize the microstructure and electrocatalytic activities of the np-PtRuCuW. The [...] Read more.

We have prepared a multi-component nanoporous PtRuCuW (np-PtRuCuW) electrocatalyst via a combined chemical dealloying and mechanical alloying process. The X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrochemical measurements have been applied to characterize the microstructure and electrocatalytic activities of the np-PtRuCuW. The np-PtRuCuW catalyst has a unique three-dimensional bi-continuous ligament structure and the length scale is 2.0 ± 0.3 nm. The np-PtRuCuW catalyst shows a relatively high level of activity normalized to mass (467.1 mA mg_Pt⁻¹) and electrochemically active surface area (1.8 mA cm⁻²) compared to the state-of-the-art commercial PtC and PtRu catalyst at anode. Although the CO stripping peak of np-PtRuCuW 0.47 V (vs. saturated calomel electrode, SCE) is more positive than PtRu, there is a 200 mV negative shift compared to PtC (0.67 V vs. SCE). In addition, the half-wave potential and specific activity towards oxygen reduction of np-PtRuCuW are 0.877 V (vs. reversible hydrogen electrode, RHE) and 0.26 mA cm⁻², indicating a great enhancement towards oxygen reduction than the commercial PtC. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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Sacrificial Template-Based Synthesis of Unified Hollow Porous Palladium Nanospheres for Formic Acid Electro-Oxidation

by Xiaoyu Qiu, Hanyue Zhang, Yuxuan Dai, Fengqi Zhang, Peishan Wu, Pin Wu and Yawen Tang

Catalysts 2015, 5(2), 992-1002; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5020992 - 23 Jun 2015

Cited by 18 | Viewed by 6703

Abstract

Large scale syntheses of uniform metal nanoparticles with hollow porous structure have attracted much attention owning to their high surface area, abundant active sites and relatively efficient catalytic activity. Herein, we report a general method to synthesize hollow porous Pd nanospheres (Pd HPNSs) [...] Read more.

Large scale syntheses of uniform metal nanoparticles with hollow porous structure have attracted much attention owning to their high surface area, abundant active sites and relatively efficient catalytic activity. Herein, we report a general method to synthesize hollow porous Pd nanospheres (Pd HPNSs) by templating sacrificial SiO₂ nanoparticles with the assistance of polyallylamine hydrochloride (PAH) through layer-by-layer self-assembly. The chemically inert PAH is acting as an efficient stabilizer and complex agent to control the synthesis of Pd HPNSs, probably accounting for its long aliphatic alkyl chains, excellent coordination capability and good hydrophilic property. The physicochemical properties of Pd HPNSs are thoroughly characterized by various techniques, such as transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy. The growth mechanism of Pd HPNSs is studied based on the analysis of diverse experimental observations. The as-prepared Pd HPNSs exhibit clearly enhanced electrocatalytic activity and durability for the formic oxidation reaction (FAOR) in acid medium compared with commercial Pd black. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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628 KiB

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Phosphorus and Nitrogen Dual Doped and Simultaneously Reduced Graphene Oxide with High Surface Area as Efficient Metal-Free Electrocatalyst for Oxygen Reduction

by Xiaochang Qiao, Shijun Liao, Chenghang You and Rong Chen

Catalysts 2015, 5(2), 981-991; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5020981 - 23 Jun 2015

Cited by 123 | Viewed by 13941

Abstract

A P, N dual doped reduced graphene oxide (PN-rGO) catalyst with high surface area (376.20 m²·g⁻¹), relatively high P-doping level (1.02 at. %) and a trace amount of N (0.35 at. %) was successfully prepared using a one-step method [...] Read more.

A P, N dual doped reduced graphene oxide (PN-rGO) catalyst with high surface area (376.20 m²·g⁻¹), relatively high P-doping level (1.02 at. %) and a trace amount of N (0.35 at. %) was successfully prepared using a one-step method by directly pyrolyzing a homogenous mixture of graphite oxide (GO) and diammonium hydrogen phosphate ((NH₄)₂HPO₄) in an argon atmosphere, during which the thermal expansion, deoxidization of GO and P, N co-doping were realized simultaneously. The catalyst exhibited enhanced catalytic performances for oxygen reduction reaction (ORR) via a dominated four-electron reduction pathway, as well as superior long-term stability, better tolerance to methanol crossover than that of commercial Pt/C catalyst in an alkaline solution. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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Oxygen Reduction Reaction Activity and Durability of Pt Catalysts Supported on Titanium Carbide

by Morio Chiwata, Katsuyoshi Kakinuma, Mitsuru Wakisaka, Makoto Uchida, Shigehito Deki, Masahiro Watanabe and Hiroyuki Uchida

Catalysts 2015, 5(2), 966-980; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5020966 - 23 Jun 2015

Cited by 46 | Viewed by 8274

Abstract

We have prepared Pt nanoparticles supported on titanium carbide (TiC) (Pt/TiC) as an alternative cathode catalyst with high durability at high potentials for polymer electrolyte fuel cells. The Pt/TiC catalysts with and without heat treatment were characterized by X-ray diffraction (XRD), X-ray photoelectron [...] Read more.

We have prepared Pt nanoparticles supported on titanium carbide (TiC) (Pt/TiC) as an alternative cathode catalyst with high durability at high potentials for polymer electrolyte fuel cells. The Pt/TiC catalysts with and without heat treatment were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Hemispherical Pt nanocrystals were found to be dispersed uniformly on the TiC support after heat treatment at 600 °C in 1% H₂/N₂ (Pt/TiC-600 °C). The electrochemical properties (cyclic voltammetry, electrochemically active area (ECA), and oxygen reduction reaction (ORR) activity) of Pt/TiC-600 °C and a commercial Pt/carbon black (c-Pt/CB) were evaluated by the rotating disk electrode (RDE) technique in 0.1 M HClO₄ solution at 25 °C. It was found that the kinetically controlled mass activity for the ORR on Pt/TiC-600 °C at 0.85 V (507 A g⁻¹) was comparable to that of c-Pt/CB (527 A g⁻¹). Moreover, the durability of Pt/TiC-600 °C examined by a standard potential step protocol (E = 0.9 V↔1.3 V vs. RHE, holding 30 s at each E) was much higher than that for c-Pt/CB. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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3813 KiB

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Highly Active Non-PGM Catalysts Prepared from Metal Organic Frameworks

by Heather M. Barkholtz, Lina Chong, Zachary B. Kaiser, Tao Xu and Di-Jia Liu

Catalysts 2015, 5(2), 955-965; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5020955 - 11 Jun 2015

Cited by 34 | Viewed by 7592

Abstract

Finding inexpensive alternatives to platinum group metals (PGMs) is essential for reducing the cost of proton exchange membrane fuel cells (PEMFCs). Numerous materials have been investigated as potential replacements of Pt, of which the transition metal and nitrogen-doped carbon composites (TM/N_x/C) [...] Read more.

Finding inexpensive alternatives to platinum group metals (PGMs) is essential for reducing the cost of proton exchange membrane fuel cells (PEMFCs). Numerous materials have been investigated as potential replacements of Pt, of which the transition metal and nitrogen-doped carbon composites (TM/N_x/C) prepared from iron doped zeolitic imidazolate frameworks (ZIFs) are among the most active ones in catalyzing the oxygen reduction reaction based on recent studies. In this report, we demonstrate that the catalytic activity of ZIF-based TM/N_x/C composites can be substantially improved through optimization of synthesis and post-treatment processing conditions. Ultimately, oxygen reduction reaction (ORR) electrocatalytic activity must be demonstrated in membrane-electrode assemblies (MEAs) of fuel cells. The process of preparing MEAs using ZIF-based non-PGM electrocatalysts involves many additional factors which may influence the overall catalytic activity at the fuel cell level. Evaluation of parameters such as catalyst loading and perfluorosulfonic acid ionomer to catalyst ratio were optimized. Our overall efforts to optimize both the catalyst and MEA construction process have yielded impressive ORR activity when tested in a fuel cell system. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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Open AccessArticle

Effect of Particle Size and Operating Conditions on Pt₃Co PEMFC Cathode Catalyst Durability

by Mallika Gummalla, Sarah C. Ball, David A. Condit, Somaye Rasouli, Kang Yu, Paulo J. Ferreira, Deborah J. Myers and Zhiwei Yang

Catalysts 2015, 5(2), 926-948; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5020926 - 29 May 2015

Cited by 57 | Viewed by 9350

Abstract

The initial performance and decay trends of polymer electrolyte membrane fuel cells (PEMFC) cathodes with Pt₃Co catalysts of three mean particle sizes (4.9 nm, 8.1 nm, and 14.8 nm) with identical Pt loadings are compared. Even though the cathode based on [...] Read more.

The initial performance and decay trends of polymer electrolyte membrane fuel cells (PEMFC) cathodes with Pt₃Co catalysts of three mean particle sizes (4.9 nm, 8.1 nm, and 14.8 nm) with identical Pt loadings are compared. Even though the cathode based on 4.9 nm catalyst exhibited the highest initial electrochemical surface area (ECA) and mass activity, the cathode based on 8.1 nm catalyst showed better initial performance at high currents. Owing to the low mass activity of the large particles, the initial performance of the 14.8 nm Pt₃Co-based electrode was the lowest. The performance decay rate of the electrodes with the smallest Pt₃Co particle size was the highest and that of the largest Pt₃Co particle size was lowest. Interestingly, with increasing number of decay cycles (0.6 to 1.0 V, 50 mV/s), the relative improvement in performance of the cathode based on 8.1 nm Pt₃Co over the 4.9 nm Pt₃Co increased, owing to better stability of the 8.1 nm catalyst. The electron microprobe analysis (EMPA) of the decayed membrane-electrode assembly (MEA) showed that the amount of Co in the membrane was lower for the larger particles, and the platinum loss into the membrane also decreased with increasing particle size. This suggests that the higher initial performance at high currents with 8.1 nm Pt₃Co could be due to lower contamination of the ionomer in the electrode. Furthermore, lower loss of Co from the catalyst with increased particle size could be one of the factors contributing to the stability of ECA and mass activity of electrodes with larger cathode catalyst particles. To delineate the impact of particle size and alloy effects, these results are compared with prior work from our research group on size effects of pure platinum catalysts. The impact of PEMFC operating conditions, including upper potential, relative humidity, and temperature on the alloy catalyst decay trends, along with the EMPA analysis of the decayed MEAs, are reported. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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2667 KiB

Open AccessArticle

Electrochemical Oxidation of the Carbon Support to Synthesize Pt(Cu) and Pt-Ru(Cu) Core-Shell Electrocatalysts for Low-Temperature Fuel Cells

by Griselda Caballero-Manrique, Enric Brillas, Francesc Centellas, José Antonio Garrido, Rosa María Rodríguez and Pere-Lluís Cabot

Catalysts 2015, 5(2), 815-837; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5020815 - 30 Apr 2015

Cited by 17 | Viewed by 8461

Abstract

The synthesis of core-shell Pt(Cu) and Pt-Ru(Cu) electrocatalysts allows for a reduction in the amount of precious metal and, as was previously shown, a better CO oxidation performance can be achieved when compared to the nanoparticulated Pt and Pt-Ru ones. In this paper, [...] Read more.

The synthesis of core-shell Pt(Cu) and Pt-Ru(Cu) electrocatalysts allows for a reduction in the amount of precious metal and, as was previously shown, a better CO oxidation performance can be achieved when compared to the nanoparticulated Pt and Pt-Ru ones. In this paper, the carbon black used as the support was previously submitted to electrochemical oxidation and characterized by XPS. The new catalysts thus prepared were characterized by HRTEM, FFT, EDX, and electrochemical techniques. Cu nanoparticles were generated by electrodeposition and were further transformed into Pt(Cu) and Pt-Ru(Cu) core-shell nanoparticles by successive galvanic exchange with Pt and spontaneous deposition of Ru species, the smallest ones being 3.3 nm in mean size. The onset potential for CO oxidation was as good as that obtained for the untreated carbon, with CO stripping peak potentials about 0.1 and 0.2 V more negative than those corresponding to Pt/C and Ru-decorated Pt/C, respectively. Carbon oxidation yielded an additional improvement in the catalyst performance, because the ECSA values for hydrogen adsorption/desorption were much higher than those obtained for the non-oxidized carbon. This suggested a higher accessibility of the Pt sites in spite of having the same nanoparticle structure and mean size. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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1231 KiB

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A Facile Synthesis of Hollow Palladium/Copper Alloy Nanocubes Supported on N-Doped Graphene for Ethanol Electrooxidation Catalyst

by Zhengyu Bai, Rumeng Huang, Lu Niu, Qing Zhang, Lin Yang and Jiujun Zhang

Catalysts 2015, 5(2), 747-758; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5020747 - 23 Apr 2015

Cited by 25 | Viewed by 7277

Abstract

In this paper, a catalyst of hollow PdCu alloy nanocubes supported on nitrogen-doped graphene support (H-PdCu/ppy-NG) is successfully synthesized using a simple one-pot template-free method. Two other catalyst materials such as solid PdCu alloy particles supported on this same nitrogen-doped graphene support (PdCu/ppy-NG) [...] Read more.

In this paper, a catalyst of hollow PdCu alloy nanocubes supported on nitrogen-doped graphene support (H-PdCu/ppy-NG) is successfully synthesized using a simple one-pot template-free method. Two other catalyst materials such as solid PdCu alloy particles supported on this same nitrogen-doped graphene support (PdCu/ppy-NG) and hollow PdCu alloy nanocubes supported on the reduced graphene oxide support (H-PdCu/RGO) are also prepared using the similar synthesis conditions for comparison. It is found that, among these three catalyst materials, H-PdCu/ppy-NG gives the highest electrochemical active area and both the most uniformity and dispersibility of H-PdCu particles. Electrochemical tests show that the H-PdCu/ppy-NG catalyst can give the best electrocatalytic activity and stability towards the ethanol electrooxidation when compared to other two catalysts. Therefore, H-PdCu/ppy-NG should be a promising catalyst candidate for anodic ethanol oxidation in direct ethanol fuel cells. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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Review

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Nitrogen-Doped Carbon Nanotube and Graphene Materials for Oxygen Reduction Reactions

by Qiliang Wei, Xin Tong, Gaixia Zhang, Jinli Qiao, Qiaojuan Gong and Shuhui Sun

Catalysts 2015, 5(3), 1574-1602; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031574 - 14 Sep 2015

Cited by 191 | Viewed by 25212

Abstract

Nitrogen-doped carbon materials, including nitrogen-doped carbon nanotubes (NCNTs) and nitrogen-doped graphene (NG), have attracted increasing attention for oxygen reduction reaction (ORR) in metal-air batteries and fuel cell applications, due to their optimal properties including excellent electronic conductivity, 4e⁻ transfer and superb mechanical [...] Read more.

Nitrogen-doped carbon materials, including nitrogen-doped carbon nanotubes (NCNTs) and nitrogen-doped graphene (NG), have attracted increasing attention for oxygen reduction reaction (ORR) in metal-air batteries and fuel cell applications, due to their optimal properties including excellent electronic conductivity, 4e⁻ transfer and superb mechanical properties. Here, the recent progress of NCNTs- and NG-based catalysts for ORR is reviewed. Firstly, the general preparation routes of these two N-doped carbon-allotropes are introduced briefly, and then a special emphasis is placed on the developments of both NCNTs and NG as promising metal-free catalysts and/or catalyst support materials for ORR. All these efficient ORR electrocatalysts feature a low cost, high durability and excellent performance, and are thus the key factors in accelerating the widespread commercialization of metal-air battery and fuel cell technologies. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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1421 KiB

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Recent Advances on Electro-Oxidation of Ethanol on Pt- and Pd-Based Catalysts: From Reaction Mechanisms to Catalytic Materials

by Ye Wang, Shouzhong Zou and Wen-Bin Cai

Catalysts 2015, 5(3), 1507-1534; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031507 - 02 Sep 2015

Cited by 388 | Viewed by 24835

Abstract

The ethanol oxidation reaction (EOR) has drawn increasing interest in electrocatalysis and fuel cells by considering that ethanol as a biomass fuel has advantages of low toxicity, renewability, and a high theoretical energy density compared to methanol. Since EOR is a complex multiple-electron [...] Read more.

The ethanol oxidation reaction (EOR) has drawn increasing interest in electrocatalysis and fuel cells by considering that ethanol as a biomass fuel has advantages of low toxicity, renewability, and a high theoretical energy density compared to methanol. Since EOR is a complex multiple-electron process involving various intermediates and products, the mechanistic investigation as well as the rational design of electrocatalysts are challenging yet essential for the desired complete oxidation to CO₂. This mini review is aimed at presenting an overview of the advances in the study of reaction mechanisms and electrocatalytic materials for EOR over the past two decades with a focus on Pt- and Pd-based catalysts. We start with discussion on the mechanistic understanding of EOR on Pt and Pd surfaces using selected publications as examples. Consensuses from the mechanistic studies are that sufficient active surface sites to facilitate the cleavage of the C–C bond and the adsorption of water or its residue are critical for obtaining a higher electro-oxidation activity. We then show how this understanding has been applied to achieve improved performance on various Pt- and Pd-based catalysts through optimizing electronic and bifunctional effects, as well as by tuning their surface composition and structure. Finally we point out the remaining key problems in the development of anode electrocatalysts for EOR. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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3896 KiB

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Nanoscale Alloying in Electrocatalysts

by Shiyao Shan, Jinfang Wu, Ning Kang, Hannah Cronk, Yinguang Zhao, Wei Zhao, Zakiya Skeete, Pharrah Joseph, Bryan Trimm, Jin Luo and Chuan-Jian Zhong

Catalysts 2015, 5(3), 1465-1478; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031465 - 19 Aug 2015

Cited by 7 | Viewed by 6537

Abstract

In electrochemical energy conversion and storage, existing catalysts often contain a high percentage of noble metals such as Pt and Pd. In order to develop low-cost electrocatalysts, one of the effective strategies involves alloying noble metals with other transition metals. This strategy promises [...] Read more.

In electrochemical energy conversion and storage, existing catalysts often contain a high percentage of noble metals such as Pt and Pd. In order to develop low-cost electrocatalysts, one of the effective strategies involves alloying noble metals with other transition metals. This strategy promises not only significant reduction of noble metals but also the tunability for enhanced catalytic activity and stability in comparison with conventional catalysts. In this report, some of the recent approaches to developing alloy catalysts for electrocatalytic oxygen reduction reaction in fuel cells will be highlighted. Selected examples will be also discussed to highlight insights into the structural and electrocatalytic properties of nanoalloy catalysts, which have implications for the design of low-cost, active, and durable catalysts for electrochemical energy production and conversion reactions. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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Advances in Ceramic Supports for Polymer Electrolyte Fuel Cells

by Oran Lori and Lior Elbaz

Catalysts 2015, 5(3), 1445-1464; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031445 - 17 Aug 2015

Cited by 65 | Viewed by 9739

Abstract

Durability of catalyst supports is a technical barrier for both stationary and transportation applications of polymer-electrolyte-membrane fuel cells. New classes of non-carbon-based materials were developed in order to overcome the current limitations of the state-of-the-art carbon supports. Some of these materials are designed [...] Read more.

Durability of catalyst supports is a technical barrier for both stationary and transportation applications of polymer-electrolyte-membrane fuel cells. New classes of non-carbon-based materials were developed in order to overcome the current limitations of the state-of-the-art carbon supports. Some of these materials are designed and tested to exceed the US DOE lifetime goals of 5000 or 40,000 hrs for transportation and stationary applications, respectively. In addition to their increased durability, the interactions between some new support materials and metal catalysts such as Pt result in increased catalyst activity. In this review, we will cover the latest studies conducted with ceramic supports based on carbides, oxides, nitrides, borides, and some composite materials. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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Recent Development of Pd-Based Electrocatalysts for Proton Exchange Membrane Fuel Cells

by Hui Meng, Dongrong Zeng and Fangyan Xie

Catalysts 2015, 5(3), 1221-1274; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031221 - 15 Jul 2015

Cited by 83 | Viewed by 11206

Abstract

This review selectively summarizes the latest developments in the Pd-based cataysts for low temperature proton exchange membrane fuel cells, especially in the application of formic acid oxidation, alcohol oxidation and oxygen reduction reaction. The advantages and shortcomings of the Pd-based catalysts for electrocatalysis [...] Read more.

This review selectively summarizes the latest developments in the Pd-based cataysts for low temperature proton exchange membrane fuel cells, especially in the application of formic acid oxidation, alcohol oxidation and oxygen reduction reaction. The advantages and shortcomings of the Pd-based catalysts for electrocatalysis are analyzed. The influence of the structure and morphology of the Pd materials on the performance of the Pd-based catalysts were described. Finally, the perspectives of future trends on Pd-based catalysts for different applications were considered. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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Recent Progress on Fe/N/C Electrocatalysts for the Oxygen Reduction Reaction in Fuel Cells

by Jing Liu, Erling Li, Mingbo Ruan, Ping Song and Weilin Xu

Catalysts 2015, 5(3), 1167-1192; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5031167 - 06 Jul 2015

Cited by 67 | Viewed by 11652

Abstract

In order to reduce the overall system cost, the development of inexpensive, high-performance and durable oxygen reduction reaction (ORR)N, Fe-codoped carbon-based (Fe/N/C) electrocatalysts to replace currently used Pt-based catalysts has become one of the major topics in research on fuel cells. This review [...] Read more.

In order to reduce the overall system cost, the development of inexpensive, high-performance and durable oxygen reduction reaction (ORR)N, Fe-codoped carbon-based (Fe/N/C) electrocatalysts to replace currently used Pt-based catalysts has become one of the major topics in research on fuel cells. This review paper lays the emphasis on introducing the progress made over the recent five years with a detailed discussion of recent work in the area of Fe/N/C electrocatalysts for ORR and the possible Fe-based active sites. Fe-based materials prepared by simple pyrolysis of transition metal salt, carbon support, and nitrogen-rich small molecule or polymeric compound are mainly reviewed due to their low cost, high performance, long stability and because they are the most promising for replacing currently used Pt-based catalysts in the progress of fuel cell commercialization. Additionally, Fe-base catalysts with small amount of Fe or new structure of Fe/Fe₃C encased in carbon layers are presented to analyze the effect of loading and existence form of Fe on the ORR catalytic activity in Fe-base catalyst. The proposed catalytically Fe-centered active sites and reaction mechanisms from various authors are also discussed in detail, which may be useful for the rational design of high-performance, inexpensive, and practical Fe-base ORR catalysts in future development of fuel cells. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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22504 KiB

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Recent Advances in Carbon Supported Metal Nanoparticles Preparation for Oxygen Reduction Reaction in Low Temperature Fuel Cells

by Yaovi Holade, Nihat Ege Sahin, Karine Servat, Teko W. Napporn and Kouakou B. Kokoh

Catalysts 2015, 5(1), 310-348; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5010310 - 06 Mar 2015

Cited by 90 | Viewed by 22267

Abstract

The oxygen reduction reaction (ORR) is the oldest studied and most challenging of the electrochemical reactions. Due to its sluggish kinetics, ORR became the major contemporary technological hurdle for electrochemists, as it hampers the commercialization of fuel cell (FC) technologies. Downsizing the metal [...] Read more.

The oxygen reduction reaction (ORR) is the oldest studied and most challenging of the electrochemical reactions. Due to its sluggish kinetics, ORR became the major contemporary technological hurdle for electrochemists, as it hampers the commercialization of fuel cell (FC) technologies. Downsizing the metal particles to nanoscale introduces unexpected fundamental modifications compared to the corresponding bulk state. To address these fundamental issues, various synthetic routes have been developed in order to provide more versatile carbon-supported low platinum catalysts. Consequently, the approach of using nanocatalysts may overcome the drawbacks encountered in massive materials for energy conversion. This review paper aims at summarizing the recent important advances in carbon-supported metal nanoparticles preparation from colloidal methods (microemulsion, polyol, impregnation, Bromide Anion Exchange…) as cathode material in low temperature FCs. Special attention is devoted to the correlation of the structure of the nanoparticles and their catalytic properties. The influence of the synthesis method on the electrochemical properties of the resulting catalysts is also discussed. Emphasis on analyzing data from theoretical models to address the intrinsic and specific electrocatalytic properties, depending on the synthetic method, is incorporated throughout. The synthesis process-nanomaterials structure-catalytic activity relationships highlighted herein, provide ample new rational, convenient and straightforward strategies and guidelines toward more effective nanomaterials design for energy conversion. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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Design of Pt/Carbon Xerogel Catalysts for PEM Fuel Cells

by Nathalie Job, Stéphanie D. Lambert, Anthony Zubiaur, Chongjiang Cao and Jean-Paul Pirard

Catalysts 2015, 5(1), 40-57; https://0-doi-org.brum.beds.ac.uk/10.3390/catal5010040 - 28 Jan 2015

Cited by 15 | Viewed by 8885

Abstract

The design of efficient catalytic layers of proton exchange membrane fuel cells (PEMFCs) requires the preparation of highly-loaded and highly-dispersed Pt/C catalysts. During the last few years, our work focused on the preparation of Pt/carbon xerogel electrocatalysts, starting from simple impregnation techniques that [...] Read more.

The design of efficient catalytic layers of proton exchange membrane fuel cells (PEMFCs) requires the preparation of highly-loaded and highly-dispersed Pt/C catalysts. During the last few years, our work focused on the preparation of Pt/carbon xerogel electrocatalysts, starting from simple impregnation techniques that were further optimized via the strong electrostatic adsorption (SEA) method to reach high dispersion and a high metal weight fraction. The SEA method, which consists of the optimization of the precursor/support electrostatic impregnation through an adequate choice of the impregnation pH with regard to the support surface chemistry, leads to very well-dispersed Pt/C samples with a maximum 8 wt.% Pt after drying and reduction under H₂. To increase the metal loading, the impregnation-drying-reduction cycle of the SEA method can be repeated several times, either with fresh Pt precursor solution or with the solution recycled from the previous cycle. In each case, a high dispersion (Pt particle size ~3 nm) is obtained. Finally, the procedure can be simplified by combination of the SEA technique with dry impregnation, leading to no Pt loss during the procedure. Full article

(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)

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