Research

11 pages, 1378 KiB

Open AccessArticle

One-Pot Synthesis of Pt Nanobowls Assembled from Ultrafine Nanoparticles for Methanol Oxidation Reaction

by Shoulin Zhang, Pu Wang, Yaoshun Chen, Wenqing Yao, Zhijuan Li and Yawen Tang

Nanomaterials 2022, 12(19), 3471; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12193471 - 04 Oct 2022

Cited by 2 | Viewed by 1140

Simultaneously engineering a bowl-like and ultrafine nano-size structure offers an attractive route to not only increase the utilization efficiency of noble metals, the specific surface areas and the availability of active sites, but also boost the structural robustness and long-term stability. However, a [...] Read more.

Simultaneously engineering a bowl-like and ultrafine nano-size structure offers an attractive route to not only increase the utilization efficiency of noble metals, the specific surface areas and the availability of active sites, but also boost the structural robustness and long-term stability. However, a great challenge remains in terms of the methods of synthesis. Herein, we report a facile one-pot hydrothermal method for the preparation of hollow porous Pt nanobowls (NBs) assembled from ultrafine particles. N,N′-methylenebisacrylamide (MBAA) acts as a structure-directing agent that forms a self-template with Pt ions and drives the nucleation and assembly of Pt metals, resulting in the fabrication of Pt NBs from ultrafine particles. By virtue of their unique structure and morphology, the optimized Pt NBs exhibited enhanced electrocatalytic methanol oxidation reaction (MOR) activity with 3.1-fold greater mass activity and 2.6-fold greater specific activities compared with those of commercial Pt black catalysts, as well as excellent stability and anti-poisoning ability. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cell Reactions in Alkaline Media)

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15 pages, 4826 KiB

Open AccessArticle

Facile Synthesis of Low-Cost Copper-Silver and Cobalt-Silver Alloy Nanoparticles on Reduced Graphene Oxide as Efficient Electrocatalysts for Oxygen Reduction Reaction in Alkaline Media

by Jadranka Milikić, Sara Knežević, Stevan Stojadinović, Mabkhoot Alsaiari, Farid A. Harraz, Diogo M. F. Santos and Biljana Šljukić

Nanomaterials 2022, 12(15), 2657; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12152657 - 02 Aug 2022

Cited by 3 | Viewed by 1746

Abstract

Copper-silver and cobalt-silver alloy nanoparticles deposited on reduced graphene oxide (CuAg/rGO and CoAg/rGO) were synthesized and examined as electrocatalysts for oxygen reduction reaction (ORR) and hydrogen peroxide reduction reaction (HPRR) in alkaline media. Characterization of the prepared samples was done by transmission electron [...] Read more.

Copper-silver and cobalt-silver alloy nanoparticles deposited on reduced graphene oxide (CuAg/rGO and CoAg/rGO) were synthesized and examined as electrocatalysts for oxygen reduction reaction (ORR) and hydrogen peroxide reduction reaction (HPRR) in alkaline media. Characterization of the prepared samples was done by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction analysis (XRD), and scanning electron microscopy with integrated energy-dispersive X-ray spectroscopy (SEM-EDS). CuAg/rGO and CoAg/rGO nanoparticles diameter ranged from 0.4 to 9.2 nm. The Ag loading was ca. 40 wt.% for both electrocatalysts, with that for Cu and Co being 35 and 17 wt.%, respectively. CoAg/rGO electrocatalyst showed a Tafel slope of 109 mV dec⁻¹, significantly lower than that for CuAg/rGO (184 mV dec⁻¹), suggesting faster ORR kinetics. Additionally, a higher diffusion current density was obtained for CoAg/rGO (−2.63 mA cm⁻²) than for CuAg/rGO (−1.74 mA cm⁻²). The average value of the number of electrons transferred during ORR was 2.8 for CuAg/rGO and 3.3 for CoAg/rGO electrocatalyst, further confirming the higher ORR activity of the latter. On the other hand, CuAg/rGO showed higher peak current densities (−3.96 mA cm⁻²) for HPRR compared to those recorded for CoAg/rGO electrocatalyst (−1.96 mA cm⁻²). Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cell Reactions in Alkaline Media)

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12 pages, 1662 KiB

Open AccessArticle

Carbon Nanotubes Interconnected NiCo Layered Double Hydroxide Rhombic Dodecahedral Nanocages for Efficient Oxygen Evolution Reaction

by Meng Li, Yujie Huang, Jiaqi Lin, Meize Li, Mengqi Jiang, Linfei Ding, Dongmei Sun, Kai Huang and Yawen Tang

Nanomaterials 2022, 12(6), 1015; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12061015 - 20 Mar 2022

Cited by 5 | Viewed by 2445

Abstract

Proper control of a 3d transition metal-based catalyst with advanced structures toward oxygen evolution reaction (OER) with a more feasible synthesis strategy is of great significance for sustainable energy-related devices. Herein, carbon nanotube interconnected NiCo layered double hydroxide rhombic dodecahedral nanocages (NiCo-LDH [...] Read more.

Proper control of a 3d transition metal-based catalyst with advanced structures toward oxygen evolution reaction (OER) with a more feasible synthesis strategy is of great significance for sustainable energy-related devices. Herein, carbon nanotube interconnected NiCo layered double hydroxide rhombic dodecahedral nanocages (NiCo-LDH RDC@CNTs) were developed here with the assistance of a feasible zeolitic imidazolate framework (ZIF) self-sacrificing template strategy as a highly efficient OER electrocatalyst. Profited by the well-fined rhombic dodecahedral nanocage architecture, CNTs’ interconnected characteristic and structural feature of the vertically aligned nanosheets, the as-synthesized NiCo-LDH RDC@CNTs integrated large exposed active surface areas, enhanced electron transfer capacity and multidimensional mass diffusion channels, and thereby collaboratively afforded the remarkable electrocatalytic performance of the OER. Specifically, the designed NiCo-LDH RDC@CNTs exhibited a distinguished OER activity, which only required a low overpotential of 255 mV to reach a current density of 10 mA cm⁻² for the OER. For the stability, no obvious current attenuation was detected, even after continuous operation for more than 27 h. We certainly believe that the current extraordinary OER activity combined with the robust stability of NiCo-LDH RDC@CNTs enables it to be a great candidate electrocatalyst for economical and sustainable energy-related devices. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cell Reactions in Alkaline Media)

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9 pages, 2235 KiB

Open AccessArticle

Cyanogel-Derived Synthesis of Porous PdFe Nanohydrangeas as Electrocatalysts for Oxygen Reduction Reaction

by Jinxin Wan, Zhenyuan Liu, Xiaoyu Yang, Peng Cheng and Chao Yan

Nanomaterials 2021, 11(12), 3382; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11123382 - 13 Dec 2021

Cited by 9 | Viewed by 2237

Abstract

It is important to develop cost-efficient electrocatalysts used in the oxygen reduction reaction (ORR) for widespread applications in fuel cells. Palladium (Pd) is a promising catalyst, due to its more abundant reserves and lower price than platinum (Pt), and doping an earth-abundant 3 [...] Read more.

It is important to develop cost-efficient electrocatalysts used in the oxygen reduction reaction (ORR) for widespread applications in fuel cells. Palladium (Pd) is a promising catalyst, due to its more abundant reserves and lower price than platinum (Pt), and doping an earth-abundant 3d-transition metal M into Pd to form Pd–M bimetallic alloys may not only further reduce the use of expensive Pd but also promote the electrocatalytic performance of ORR, owing to the synergistic effect between Pd and M. Here we report a cyanogel-derived synthesis of PdFe alloys with porous nanostructure via a simple coinstantaneous reduction reaction by using K₂Pd^IICl₄/K₄Fe^II(CN)₆ cyanogel as precursor. The synthesized PdFe alloys possess hydrangea-like morphology and porous nanostructure, which are beneficial to the electrochemical performance in ORR. The onset potential of the porous PdFe nanohydrangeas is determined to be 0.988 V, which is much more positive than that of commercial Pt/C catalyst (0.976 V) and Pd black catalyst (0.964 V). Resulting from the unique structural advantages and synergetic effect between bimetals, the synthesized PdFe nanohydrangeas with porous structure have outstanding electrocatalytic activity and stability for ORR, compared with the commercial Pd black and Pt/C. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cell Reactions in Alkaline Media)

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15 pages, 2291 KiB

Open AccessArticle

Ultra-Low Pt Loading in PtCo Catalysts for the Hydrogen Oxidation Reaction: What Role Do Co Nanoparticles Play?

by Felipe de Jesús Anaya-Castro, Mara Beltrán-Gastélum, Omar Morales Soto, Sergio Pérez-Sicairos, Shui Wai Lin, Balter Trujillo-Navarrete, Francisco Paraguay-Delgado, Luis Javier Salazar-Gastélum, Tatiana Romero-Castañón, Edgar Reynoso-Soto, Rosa María Félix-Navarro and Moisés Israel Salazar-Gastélum

Nanomaterials 2021, 11(11), 3156; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11113156 - 22 Nov 2021

Cited by 10 | Viewed by 2273

Abstract

The effect of the nature of the catalyst on the performance and mechanism of the hydrogen oxidation reaction (HOR) is discussed for the first time in this work. HOR is an anodic reaction that takes place in anionic exchange membrane fuel cells (AEMFCs) [...] Read more.

The effect of the nature of the catalyst on the performance and mechanism of the hydrogen oxidation reaction (HOR) is discussed for the first time in this work. HOR is an anodic reaction that takes place in anionic exchange membrane fuel cells (AEMFCs) and hydrogen pumps (HPs). Among the investigated catalysts, Pt exhibited the best performance in the HOR. However, the cost and the availability limit the usage. Co is incorporated as a co-catalyst due to its oxophylic nature. Five different PtCo catalysts with different Pt loading values were synthesized in order to decrease Pt loading. The catalytic activities and the reaction mechanism were studied via electrochemical techniques, and it was found that both features are a function of Pt loading; low-Pt-loading catalysts (Pt loading < 2.7%) led to a high half-wave potential in the hydrogen oxidation reaction, which is related to higher activation energy and an intermediate Tafel slope value, related to a mixed HOR mechanism. However, catalysts with moderate Pt loading (Pt loading > 3.1%) exhibited lower E_1/2 than the other catalysts and exhibited a mechanism similar to that of commercial Pt catalysts. Our results demonstrate that Co plays an active role in the HOR, facilitating H_ads desorption, which is the rate-determining step (RDS) in the mechanism of the HOR. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cell Reactions in Alkaline Media)

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13 pages, 2441 KiB

Open AccessArticle

Cobalt–Iron–Phosphate Hydrogen Evolution Reaction Electrocatalyst for Solar-Driven Alkaline Seawater Electrolyzer

by Chiho Kim, Seunghun Lee, Seong Hyun Kim, Jaehan Park, Shinho Kim, Se-Hun Kwon, Jong-Seong Bae, Yoo Sei Park and Yangdo Kim

Nanomaterials 2021, 11(11), 2989; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11112989 - 06 Nov 2021

Cited by 12 | Viewed by 3497

Abstract

Seawater splitting represents an inexpensive and attractive route for producing hydrogen, which does not require a desalination process. Highly active and durable electrocatalysts are required to sustain seawater splitting. Herein we report the phosphidation-based synthesis of a cobalt–iron–phosphate ((Co,Fe)PO₄) electrocatalyst for [...] Read more.

Seawater splitting represents an inexpensive and attractive route for producing hydrogen, which does not require a desalination process. Highly active and durable electrocatalysts are required to sustain seawater splitting. Herein we report the phosphidation-based synthesis of a cobalt–iron–phosphate ((Co,Fe)PO₄) electrocatalyst for hydrogen evolution reaction (HER) toward alkaline seawater splitting. (Co,Fe)PO₄ demonstrates high HER activity and durability in alkaline natural seawater (1 M KOH + seawater), delivering a current density of 10 mA/cm² at an overpotential of 137 mV. Furthermore, the measured potential of the electrocatalyst ((Co,Fe)PO₄) at a constant current density of −100 mA/cm² remains very stable without noticeable degradation for 72 h during the continuous operation in alkaline natural seawater, demonstrating its suitability for seawater applications. Furthermore, an alkaline seawater electrolyzer employing the non-precious-metal catalysts demonstrates better performance (1.625 V at 10 mA/cm²) than one employing precious metal ones (1.653 V at 10 mA/cm²). The non-precious-metal-based alkaline seawater electrolyzer exhibits a high solar-to-hydrogen (STH) efficiency (12.8%) in a commercial silicon solar cell. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cell Reactions in Alkaline Media)

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9 pages, 2616 KiB

Open AccessArticle

Facile Synthesis of MoP-RuP2 with Abundant Interfaces to Boost Hydrogen Evolution Reactions in Alkaline Media

by Zhi Chen, Ying Zhao, Yuxiao Gao, Zexing Wu and Lei Wang

Nanomaterials 2021, 11(9), 2347; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11092347 - 09 Sep 2021

Cited by 5 | Viewed by 2095

Abstract

Exploiting efficient electrocatalysts for hydrogen evolution reactions (HERs) is important for boosting the large-scale applications of hydrogen energy. Herein, MoP-RuP₂ encapsulated in N,P-codoped carbon (MoP-RuP₂@NPC) with abundant interfaces were prepared via a facile avenue with the low-toxic melamine phosphate as [...] Read more.

Exploiting efficient electrocatalysts for hydrogen evolution reactions (HERs) is important for boosting the large-scale applications of hydrogen energy. Herein, MoP-RuP₂ encapsulated in N,P-codoped carbon (MoP-RuP₂@NPC) with abundant interfaces were prepared via a facile avenue with the low-toxic melamine phosphate as the phosphorous resource. Moreover, the obtained electrocatalyst possessed a porous nanostructure, had abundant exposed active sites and improved the mass transport during the electrocatalytic process. Due to the above merits, the prepared MoP-RuP₂@NPC delivered a greater electrocatalytic performance for HERs (50 mV@10 mA cm⁻²) relative to RuP₂@NPC (120 mV) and MoP@NPC (195 mV) in 1 M KOH. Moreover, an ultralow potential of 1.6 V was required to deliver a current density of 10 mA cm⁻² in the two-electrode configuration for overall water splitting. For practical applications, intermittent solar energy, wind energy and thermal energy were utilized to drive the electrolyzer to generate hydrogen gas. This work provides a novel and facile strategy for designing highly efficient and stable nanomaterials toward hydrogen production. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cell Reactions in Alkaline Media)

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10 pages, 4544 KiB

Open AccessArticle

Self-Supported Defect-Rich Au-Based Nanostructures as Robust Bifunctional Catalysts for the Methanol Oxidation Reaction and Oxygen Reduction Reaction in an Alkaline Medium

by Yuanyuan Tao, Xiu Liang, Guanchen Xu, Dongwei Li, Yong Li, Na Zhang, Yingzhou Chen, Xifeng Jiang and Hongyu Gong

Nanomaterials 2021, 11(9), 2193; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11092193 - 26 Aug 2021

Cited by 6 | Viewed by 1893

Abstract

Recently, alkaline direct methanol fuel cells have made great progress with the development of alkaline electrocatalysis, and a wide variety of catalysts have been explored for methanol oxidation reaction (MOR)and oxygen reduction reaction (ORR). However, the slow kinetics of the MOR and ORR [...] Read more.

Recently, alkaline direct methanol fuel cells have made great progress with the development of alkaline electrocatalysis, and a wide variety of catalysts have been explored for methanol oxidation reaction (MOR)and oxygen reduction reaction (ORR). However, the slow kinetics of the MOR and ORR remain a great challenge. In this paper, self-supported defect-rich AuCu was obtained by a convenient one-pot strategy. Self-supported AuCu presented a branched, porous nanostructure. The nanobranch consisted of several 13 nm skeletons, which connected in the kink of the structure. Different growth directions co-existed at the kink, and the twin boundaries and dislocations as defects were observed. When the Au-based nanostructure functioned as an electrocatalyst, it showed robust MOR and ORR performance. For the MOR, the forward peak current was 2.68 times greater than that of Au/C; for the ORR, the activity was close to that of Pt/C and significantly better than that of Au/C. In addition, it possessed superior electrochemical stability for MOR and ORR. Finally, an in-depth exploration of the impact of surface defects and electrochemical Cu removal on MOR and ORR activity was carried out to explain the MOR and ORR’s catalytic performance. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cell Reactions in Alkaline Media)

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