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12 pages, 7864 KiB

Open AccessArticle

PbS Quantum Dots-Decorated BiVO₄ Photoanodes for Highly Efficient Photoelectrochemical Hydrogen Production

by Joo-Won Seo, Seung-Beom Ha, In-Cheul Song and Jae-Yup Kim

Nanomaterials 2023, 13(5), 799; https://0-doi-org.brum.beds.ac.uk/10.3390/nano13050799 - 22 Feb 2023

Cited by 3 | Viewed by 1569

While metal oxides such as TiO₂, Fe₂O₃, WO₃, and BiVO₄ have been previously studied for their potential as photoanodes in photoelectrochemical (PEC) hydrogen production, their relatively wide band-gap limits their photocurrent, making them unsuitable [...] Read more.

While metal oxides such as TiO₂, Fe₂O₃, WO₃, and BiVO₄ have been previously studied for their potential as photoanodes in photoelectrochemical (PEC) hydrogen production, their relatively wide band-gap limits their photocurrent, making them unsuitable for the efficient utilization of incident visible light. To overcome this limitation, we propose a new approach for highly efficient PEC hydrogen production based on a novel photoanode composed of BiVO₄/PbS quantum dots (QDs). Crystallized monoclinic BiVO₄ films were prepared via a typical electrodeposition process, followed by the deposition of PbS QDs using a successive ionic layer adsorption and reaction (SILAR) method to form a p-n heterojunction. This is the first time that narrow band-gap QDs were applied to sensitize a BiVO₄ photoelectrode. The PbS QDs were uniformly coated on the surface of nanoporous BiVO₄, and their optical band-gap was reduced by increasing the number of SILAR cycles. However, this did not affect the crystal structure and optical properties of the BiVO₄. By decorating the surface of BiVO₄ with PbS QDs, the photocurrent was increased from 2.92 to 4.88 mA/cm² (at 1.23 V_RHE) for PEC hydrogen production, resulting from the enhanced light-harvesting capability arising from the narrow band-gap of the PbS QDs. Moreover, the introduction of a ZnS overlayer on the BiVO₄/PbS QDs further improved the photocurrent to 5.19 mA/cm², attributed to the reduction in interfacial charge recombination. Full article

(This article belongs to the Special Issue Design of Nanocatalysts and Electrodes: Application to Fuel Cell and Water Electrolysis)

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10 pages, 2021 KiB

Open AccessArticle

Activity Quantification of Fuel Cell Catalysts via Sequential Poisoning by Multiple Reaction Inhibitors

by Yunjin Kim, Jiho Min, Keonwoo Ko, Bathinapatla Sravani, Sourabh S. Chougule, Yoonseong Choi, Hyeonwoo Choi, SeoYeong Hong and Namgee Jung

Nanomaterials 2022, 12(21), 3800; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12213800 - 28 Oct 2022

Cited by 1 | Viewed by 1146

Abstract

The development of non−Pt or carbon−based catalysts for anion exchange membrane fuel cells (AEMFCs) requires identification of the active sites of the catalyst. Since not only metals but also carbon materials exhibit oxygen reduction reaction (ORR) activity in alkaline conditions, the contribution of [...] Read more.

The development of non−Pt or carbon−based catalysts for anion exchange membrane fuel cells (AEMFCs) requires identification of the active sites of the catalyst. Since not only metals but also carbon materials exhibit oxygen reduction reaction (ORR) activity in alkaline conditions, the contribution of carbon-based materials to ORR performance should also be thoroughly analyzed. However, the conventional CN⁻ poisoning experiments, which are mainly used to explain the main active site of M−N−C catalysts, are limited to only qualitative discussions, having the potential to make fundamental errors. Here, we report a modified electrochemical analysis to quantitatively investigate the contribution of the metal and carbon active sites to ORR currents at a fixed potential by sequentially performing chronoamperometry with two reaction inhibitors, CN⁻ and benzyl trimethylammonium (BTMA⁺). As a result, we discover how to quantify the individual contributions of two active sites (Pt nanoparticles and carbon support) of carbon−supported Pt (Pt/C) nanoparticles as a model catalyst. This study is expected to provide important clues for the active site analysis of carbon-supported non−Pt catalysts, such as M−N−C catalysts composed of heterogeneous elements. Full article

(This article belongs to the Special Issue Design of Nanocatalysts and Electrodes: Application to Fuel Cell and Water Electrolysis)

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11 pages, 71590 KiB

Open AccessArticle

Excellent Electrocatalytic Hydrogen Evolution Reaction Performances of Partially Graphitized Activated-Carbon Nanobundles Derived from Biomass Human Hair Wastes

by Sankar Sekar, Dae Hyun Sim and Sejoon Lee

Nanomaterials 2022, 12(3), 531; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12030531 - 03 Feb 2022

Cited by 14 | Viewed by 2722

Abstract

Carbonaceous materials play a vital role as an appropriate catalyst for electrocatalytic hydrogen production. Aiming at realizing the highly efficient hydrogen evolution reaction (HER), the partially graphitized activated-carbon nanobundles were synthesized as a high-performance HER electrocatalyst by using biomass human hair ashes through [...] Read more.

Carbonaceous materials play a vital role as an appropriate catalyst for electrocatalytic hydrogen production. Aiming at realizing the highly efficient hydrogen evolution reaction (HER), the partially graphitized activated-carbon nanobundles were synthesized as a high-performance HER electrocatalyst by using biomass human hair ashes through the high-temperature KOH activation at two different temperatures of 600 and 700 °C. Due to the partial graphitization, the 700 °C KOH-activated partially graphitized activated-carbon nanobundles exhibited higher electrical conductivity as well as higher textural porosity than those of the amorphous activated-carbon nanobundles that had been prepared by the KOH activation at 600 °C. As a consequence, the 700 °C-activated partially graphitized activated-carbon nanobundles showed the extraordinarily high HER activity with the very low overpotential (≈16 mV at 10 mA/cm² in 0.5 M H₂SO₄) and the small Tafel slope (≈51 mV/dec). These results suggest that the human hair-derived partially graphitized activated-carbon nanobundles can be effectively utilized as a high-performance HER electrocatalyst in future hydrogen-energy technology. Full article

(This article belongs to the Special Issue Design of Nanocatalysts and Electrodes: Application to Fuel Cell and Water Electrolysis)

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11 pages, 2285 KiB

Open AccessArticle

Highly Enhanced OER Performance by Er-Doped Fe-MOF Nanoarray at Large Current Densities

by Yan Ma, Yujie Miao, Guomei Mu, Dunmin Lin, Chenggang Xu, Wen Zeng and Fengyu Xie

Nanomaterials 2021, 11(7), 1847; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11071847 - 16 Jul 2021

Cited by 12 | Viewed by 3791

Abstract

Great expectations have been held for the electrochemical splitting of water for producing hydrogen as a significant carbon-neutral technology aimed at solving the global energy crisis and greenhouse gas issues. However, the oxygen evolution reaction (OER) process must be energetically catalyzed over a [...] Read more.

Great expectations have been held for the electrochemical splitting of water for producing hydrogen as a significant carbon-neutral technology aimed at solving the global energy crisis and greenhouse gas issues. However, the oxygen evolution reaction (OER) process must be energetically catalyzed over a long period at high output, leading to challenges for efficient and stable processing of electrodes for practical purposes. Here, we first prepared Fe-MOF nanosheet arrays on nickel foam via rare-earth erbium doping (Er_0.4 Fe-MOF/NF) and applied them as OER electrocatalysts. The Er_0.4 Fe-MOF/NF exhibited wonderful OER performance and could yield a 100 mA cm⁻² current density at an overpotential of 248 mV with outstanding long-term electrochemical durability for at least 100 h. At large current densities of 500 and 1000 mA cm⁻², overpotentials of only 297 mV and 326 mV were achieved, respectively, revealing its potential in industrial applications. The enhancement was attributed to the synergistic effects of the Fe and Er sites, with Er playing a supporting role in the engineering of the electronic states of the Fe sites to endow them with enhanced OER activity. Such a strategy of engineering the OER activity of Fe-MOF via rare-earth ion doping paves a new avenue to design other MOF catalysts for industrial OER applications. Full article

(This article belongs to the Special Issue Design of Nanocatalysts and Electrodes: Application to Fuel Cell and Water Electrolysis)

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15 pages, 4245 KiB

Open AccessArticle

Influence of Electrochemical Pretreatment Conditions of PtCu/C Alloy Electrocatalyst on Its Activity

by Angelina Pavlets, Anastasia Alekseenko, Vladislav Menshchikov, Sergey Belenov, Vadim Volochaev, Ilya Pankov, Olga Safronenko and Vladimir Guterman

Nanomaterials 2021, 11(6), 1499; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11061499 - 06 Jun 2021

Cited by 14 | Viewed by 2566

Abstract

A carbon supported PtCu_x/C catalyst, which demonstrates high activity in the oxygen electroreduction and methanol electrooxidation reactions in acidic media, has been obtained using a method of chemical reduction of Pt (IV) and Cu (2+) in the liquid phase. It has [...] Read more.

A carbon supported PtCu_x/C catalyst, which demonstrates high activity in the oxygen electroreduction and methanol electrooxidation reactions in acidic media, has been obtained using a method of chemical reduction of Pt (IV) and Cu (2+) in the liquid phase. It has been found that the potential range of the preliminary voltammetric activation of the PtCu_x/C catalyst has a significant effect on the de-alloyed material activity in the oxygen electroreduction reaction (ORR). High-resolution transmission electron microscopy (HRTEM) demonstrates that there are differences in the structures of the as-prepared material and the materials activated in different potential ranges. In this case, there is practically no difference in the composition of the PtCu_x-y/C materials obtained after activation in different conditions. The main reason for the established effect, apparently, is the reorganized features of the bimetallic nanoparticles’ surface structure, which depend on the value of the limiting anodic potential in the activation process. The effect of the activation conditions on the catalyst’s activity in the methanol electrooxidation reaction is less pronounced. Full article

(This article belongs to the Special Issue Design of Nanocatalysts and Electrodes: Application to Fuel Cell and Water Electrolysis)

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13 pages, 2676 KiB

Open AccessArticle

Black-Si as a Photoelectrode

by Denver P. Linklater, Fatima Haydous, Cheng Xi, Daniele Pergolesi, Jingwen Hu, Elena P. Ivanova, Saulius Juodkazis, Thomas Lippert and Jurga Juodkazytė

Nanomaterials 2020, 10(5), 873; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10050873 - 01 May 2020

Cited by 9 | Viewed by 3770

Abstract

The fabrication and characterization of photoanodes based on black-Si (b-Si) are presented using a photoelectrochemical cell in NaOH solution. B-Si was fabricated by maskless dry plasma etching and was conformally coated by tens-of-nm of TiO₂ using atomic layer deposition (ALD) with a [...] Read more.

The fabrication and characterization of photoanodes based on black-Si (b-Si) are presented using a photoelectrochemical cell in NaOH solution. B-Si was fabricated by maskless dry plasma etching and was conformally coated by tens-of-nm of TiO₂ using atomic layer deposition (ALD) with a top layer of CoO

_{x}

cocatalyst deposited by pulsed laser deposition (PLD). Low reflectivity

R < 5 %

of b-Si over the entire visible and near-IR (

λ < 2 μ

m) spectral range was favorable for the better absorption of light, while an increased surface area facilitated larger current densities. The photoelectrochemical performance of the heterostructured b-Si photoanode is discussed in terms of the n-n junction between b-Si and TiO₂. Full article

(This article belongs to the Special Issue Design of Nanocatalysts and Electrodes: Application to Fuel Cell and Water Electrolysis)

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11 pages, 2471 KiB

Open AccessArticle

Modulating Catalytic Activity and Durability of PtFe Alloy Catalysts for Oxygen Reduction Reaction Through Controlled Carbon Shell Formation

by Youngjin Kim, A. Anto Jeffery, Jiho Min and Namgee Jung

Nanomaterials 2019, 9(10), 1491; https://doi.org/10.3390/nano9101491 - 19 Oct 2019

Cited by 18 | Viewed by 4377

Abstract

Demand on synthetic approaches to high performance electrocatalyst with enhanced durability is increasing for fuel cell applications. In this work, we present a facile synthesis of carbon shell-coated PtFe nanoparticles by using acetylacetonates in metal precursors as carbon sources without an additional polymer [...] Read more.

Demand on synthetic approaches to high performance electrocatalyst with enhanced durability is increasing for fuel cell applications. In this work, we present a facile synthesis of carbon shell-coated PtFe nanoparticles by using acetylacetonates in metal precursors as carbon sources without an additional polymer coating process for the carbon shell formation. The carbon shell structure is systematically controlled by changing the annealing conditions such as the temperature and gas atmosphere. PtFe catalysts annealed at 700 °C under H₂-mixed N₂ gas show much higher oxygen reduction reaction (ORR) activity and superior durability compared to a Pt catalyst due to the ultrathin and porous carbon shells. In addition, when increasing the annealing temperature, the carbon shells encapsulating the PtFe nanoparticles improves the durability of the catalysts due to the enhanced crystallinity of the carbon shells. Therefore, it is demonstrated that the developed hybrid catalyst structure with the carbon shells not only allows the access of reactant molecules to the active sites for oxygen reduction reaction but also prevents the agglomeration of metal nanoparticles on carbon supports, even under harsh operating conditions. The proposed synthetic approach and catalyst structure are expected to provide more insights into the development of highly active and durable catalysts for practical fuel cell applications. Full article

(This article belongs to the Special Issue Design of Nanocatalysts and Electrodes: Application to Fuel Cell and Water Electrolysis)

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10 pages, 2261 KiB

Open AccessFeature PaperArticle

Electrochemical Analysis for Demonstrating CO Tolerance of Catalysts in Polymer Electrolyte Membrane Fuel Cells

by Jiho Min, A. Anto Jeffery, Youngjin Kim and Namgee Jung

Nanomaterials 2019, 9(10), 1425; https://0-doi-org.brum.beds.ac.uk/10.3390/nano9101425 - 08 Oct 2019

Cited by 14 | Viewed by 3471

Abstract

Since trace amounts of CO in H₂ gas produced by steam reforming of methane causes severe poisoning of Pt-based catalysts in polymer electrolyte membrane fuel cells (PEMFCs), research has been mainly devoted to exploring CO-tolerant catalysts. To test the electrochemical property of [...] Read more.

Since trace amounts of CO in H₂ gas produced by steam reforming of methane causes severe poisoning of Pt-based catalysts in polymer electrolyte membrane fuel cells (PEMFCs), research has been mainly devoted to exploring CO-tolerant catalysts. To test the electrochemical property of CO-tolerant catalysts, chronoamperometry is widely used under a CO/H₂ mixture gas atmosphere as an essential method. However, in most cases of catalysts with high CO tolerance, the conventional chronoamperometry has difficulty in showing the apparent performance difference. In this study, we propose a facile and precise test protocol to evaluate the CO tolerance via a combination of short-term chronoamperometry and a hydrogen oxidation reaction (HOR) test. The degree of CO poisoning is systematically controlled by changing the CO adsorption time. The HOR polarization curve is then measured and compared with that measured without CO adsorption. When the electrochemical properties of PtRu alloy catalysts with different atomic ratios of Pt to Ru are investigated, contrary to conventional chronoamperometry, these catalysts exhibit significant differences in their CO tolerance at certain CO adsorption times. The present work will facilitate the development of catalysts with extremely high CO tolerance and provide insights into the improvement of electrochemical methods. Full article

(This article belongs to the Special Issue Design of Nanocatalysts and Electrodes: Application to Fuel Cell and Water Electrolysis)

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