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Electrocatalytic Water Splitting
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Electrocatalytic Water Splitting

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Electrochemistry".

Deadline for manuscript submissions: closed (30 June 2021) | Viewed by 34698

Special Issue Editor

Prof. Dr. Mark Symes

E-Mail Website
Guest Editor
School of Chemistry, WestCHEM, University of Glasgow, Glasgow, UK
Interests: electrocatalysis; water splitting; nitrogen reduction; nitrogen oxides; metal-ligand coordination complexes

Special Issue Information

Dear Colleagues,

As our reliance on renewable energy sources grows, so too does our need to store this energy in order to mitigate against peaks and troughs in supply. Amongst the numerous solutions that have been proposed for this challenge, the electrolysis of water using renewables stands out due to its scalability and the potential for hydrogen to underwrite a global sustainable energy cycle.

This Special Issue of Molecules is devoted to electrocatalysis and photo-electrocatalysis of water splitting reactions, including studies on the oxygen evolution reaction, the hydrogen evolution reaction and complete water-splitting systems. Manuscripts examining theoretical and computational aspects of water-splitting electrocatalysis and photo-electrocatalysis are also welcome, as are concept articles that wish to expound new directions in electrocatalysis relating to water splitting. All scientists working in these emerging and promising fields of research are strongly encouraged to submit their original works for publication in this Special Issue.

Prof. Dr. Mark Symes
Guest Editor

Manuscript Submission Information

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Keywords

  • Oxygen evolution reaction
  • Hydrogen evolution reaction
  • Electrochemical water splitting
  • Photoelectrochemical water splitting
  • Electrocatalytic water splitting

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Published Papers (7 papers)

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Research

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12 pages, 1832 KiB  
Communication
Applying Active Learning to the Screening of Molecular Oxygen Evolution Catalysts
by Michael John Craig and Max García-Melchor
Molecules 2021, 26(21), 6362; https://doi.org/10.3390/molecules26216362 - 21 Oct 2021
Cited by 7 | Viewed by 3083
Abstract
The oxygen evolution reaction (OER) can enable green hydrogen production; however, the state-of-the-art catalysts for this reaction are composed of prohibitively expensive materials. In addition, cheap catalysts have associated overpotentials that render the reaction inefficient. This impels the search to discover novel catalysts [...] Read more.
The oxygen evolution reaction (OER) can enable green hydrogen production; however, the state-of-the-art catalysts for this reaction are composed of prohibitively expensive materials. In addition, cheap catalysts have associated overpotentials that render the reaction inefficient. This impels the search to discover novel catalysts for this reaction computationally. In this communication, we present machine learning algorithms to enhance the hypothetical screening of molecular OER catalysts. By predicting calculated binding energies using Gaussian process regression (GPR) models and applying active learning schemes, we provide evidence that our algorithm can improve computational efficiency by guiding simulations towards candidates with promising OER descriptor values. Furthermore, we derive an acquisition function that, when maximized, can identify catalysts that can exhibit theoretical overpotentials that circumvent the constraints imposed by linear scaling relations by attempting to enforce a specific mechanism. Finally, we provide a brief perspective on the appropriate sets of molecules to consider when screening complexes that could be stable and active for this reaction. Full article
(This article belongs to the Special Issue Electrocatalytic Water Splitting)
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17 pages, 3256 KiB  
Article
Insights on the Electrocatalytic Seawater Splitting at Heterogeneous Nickel-Cobalt Based Electrocatalysts Engineered from Oxidative Aniline Polymerization and Calcination
by Perla Hajjar, Marie-Agnès Lacour, Nathalie Masquelez, Julien Cambedouzou, Sophie Tingry, David Cornu and Yaovi Holade
Molecules 2021, 26(19), 5926; https://doi.org/10.3390/molecules26195926 - 30 Sep 2021
Cited by 12 | Viewed by 3660
Abstract
Given the limited access to freshwater compared to seawater, a growing interest surrounds the direct seawater electrolysis to produce hydrogen. However, we currently lack efficient electrocatalysts to selectively perform the oxygen evolution reaction (OER) over the oxidation of the chloride ions that are [...] Read more.
Given the limited access to freshwater compared to seawater, a growing interest surrounds the direct seawater electrolysis to produce hydrogen. However, we currently lack efficient electrocatalysts to selectively perform the oxygen evolution reaction (OER) over the oxidation of the chloride ions that are the main components of seawater. In this contribution, we report an engineering strategy to synthesize heterogeneous electrocatalysts by the simultaneous formation of separate chalcogenides of nickel (NiSx, x = 0, 2/3, 8/9, and 4/3) and cobalt (CoSx, x = 0 and 8/9) onto a carbon-nitrogen-sulfur nanostructured network. Specifically, the oxidative aniline polymerization in the presence of metallic cations was combined with the calcination to regulate the separate formation of various self-supported phases in order to target the multifunctional applicability as both hydrogen evolution reaction (HER) and OER in a simulated alkaline seawater. The OER’s metric current densities of 10 and 100 mA cm−2 were achieved at the bimetallic for only 1.60 and 1.63 VRHE, respectively. This high-performance was maintained in the electrolysis with a starting voltage of 1.6 V and satisfactory stability at 100 mA over 17 h. Our findings validate a high selectivity for OER of ~100%, which outperforms the previously reported data of 87–95%. Full article
(This article belongs to the Special Issue Electrocatalytic Water Splitting)
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13 pages, 2370 KiB  
Article
Influence of Chiral Compounds on the Oxygen Evolution Reaction (OER) in the Water Splitting Process
by Mirko Gazzotti, Andrea Stefani, Marco Bonechi, Walter Giurlani, Massimo Innocenti and Claudio Fontanesi
Molecules 2020, 25(17), 3988; https://doi.org/10.3390/molecules25173988 - 1 Sep 2020
Cited by 9 | Viewed by 3938
Abstract
Results are presented concerning the influence on the water splitting process of enantiopure tartaric acid present in bulk solution. Stainless steel and electrodeposited nickel are used as working electrode (WE) surface. The latter is obtained by electrodeposition on the two poles of a [...] Read more.
Results are presented concerning the influence on the water splitting process of enantiopure tartaric acid present in bulk solution. Stainless steel and electrodeposited nickel are used as working electrode (WE) surface. The latter is obtained by electrodeposition on the two poles of a magnet. The influence and role played by the chiral compound in solution has been assessed by comparing the current values, in cyclic voltammetry (CV) experiments, recorded in the potential range at which oxygen evolution reaction (OER) occurs. In the case of tartaric acid and nickel WE a spin polarization of about 4% is found. The use of the chiral environment (bulk solution) and ferromagnetic chiral Ni electrode allows for observing the OER at a more favorable potential: About 50 mV (i.e., a cathodic, less positive, shift of the potential at which the oxygen evolution is observed). Full article
(This article belongs to the Special Issue Electrocatalytic Water Splitting)
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21 pages, 2113 KiB  
Article
Application of Photo-Electrochemically Generated Hydrogen with Fuel Cell Based Micro-Combined Heat and Power: A Dynamic System Modelling Study
by Krisztian Ronaszegi, Eric S. Fraga, Jawwad Darr, Paul R. Shearing and Dan J. L. Brett
Molecules 2020, 25(1), 123; https://doi.org/10.3390/molecules25010123 - 28 Dec 2019
Cited by 6 | Viewed by 4011
Abstract
Photo-electrochemical (PEC) hydrogen generation is a promising technology and alternative to photovoltaic (PV)-electrolyser combined systems. Since there are no commercially available PEC cells and very limited field trials, a computer simulation was used to assess the efficacy of the approach for different domestic [...] Read more.
Photo-electrochemical (PEC) hydrogen generation is a promising technology and alternative to photovoltaic (PV)-electrolyser combined systems. Since there are no commercially available PEC cells and very limited field trials, a computer simulation was used to assess the efficacy of the approach for different domestic applications. Three mathematical models were used to obtain a view on how PEC generated hydrogen is able to cover demands for a representative dwelling. The analysed home was grid-connected and used a fuel cell based micro-CHP (micro-combined heat and power) system. Case studies were carried out that considered four different photo-electrode technologies to capture a range of current and possible future device efficiencies. The aim for this paper was to evaluate the system performance such as efficiency, fuel consumption and CO2 reduction capability. At the device unit level, the focus was on photo-electrode technological aspects, such as the effect of band-gap energy represented by different photo-materials on productivity of hydrogen and its uncertainty caused by the incident photon-to-current conversion efficiency (IPCE), which is highly electrode preparation specific. The presented dynamic model allows analysis of the performance of a renewable energy source integrated household with variable loads, which will aid system design and decision-making. Full article
(This article belongs to the Special Issue Electrocatalytic Water Splitting)
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12 pages, 3700 KiB  
Article
Electrochemical Hydrogen Evolution over Hydrothermally Synthesized Re-Doped MoS2 Flower-Like Microspheres
by Juan Aliaga, Pablo Vera, Juan Araya, Luis Ballesteros, Julio Urzúa, Mario Farías, Francisco Paraguay-Delgado, Gabriel Alonso-Núñez, Guillermo González and Eglantina Benavente
Molecules 2019, 24(24), 4631; https://doi.org/10.3390/molecules24244631 - 17 Dec 2019
Cited by 26 | Viewed by 5966
Abstract
In this research, we report a simple hydrothermal synthesis to prepare rhenium (Re)- doped MoS2 flower-like microspheres and the tuning of their structural, electronic, and electrocatalytic properties by modulating the insertion of Re. The obtained compounds were characterized by X-ray diffraction (XRD), [...] Read more.
In this research, we report a simple hydrothermal synthesis to prepare rhenium (Re)- doped MoS2 flower-like microspheres and the tuning of their structural, electronic, and electrocatalytic properties by modulating the insertion of Re. The obtained compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Structural, morphological, and chemical analyses confirmed the synthesis of poorly crystalline Re-doped MoS2 flower-like microspheres composed of few stacked layers. They exhibit enhanced hydrogen evolution reaction (HER) performance with low overpotential of 210 mV at current density of 10 mA/cm2, with a small Tafel slope of 78 mV/dec. The enhanced catalytic HER performance can be ascribed to activation of MoS2 basal planes and by reduction in charge transfer resistance during HER upon doping. Full article
(This article belongs to the Special Issue Electrocatalytic Water Splitting)
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16 pages, 2685 KiB  
Article
Oxygen Evolution Reaction at IrO2/Ir(Ni) Film Electrodes Prepared by Galvanic Replacement and Anodization: Effect of Precursor Ni Film Thickness
by Aikaterini Touni, Athanasios Papaderakis, Dimitrios Karfaridis, Georgios Vourlias and Sotiris Sotiropoulos
Molecules 2019, 24(11), 2095; https://doi.org/10.3390/molecules24112095 - 1 Jun 2019
Cited by 17 | Viewed by 4828
Abstract
IrO2/Ir(Ni) film electrodes of variable Ni content have been prepared via a galvanic replacement method, whereby surface layers of pre-deposited Ni are replaced by Ir, followed by electrochemical anodization. Electrodeposition of Ni on a glassy carbon electrode support has been carried [...] Read more.
IrO2/Ir(Ni) film electrodes of variable Ni content have been prepared via a galvanic replacement method, whereby surface layers of pre-deposited Ni are replaced by Ir, followed by electrochemical anodization. Electrodeposition of Ni on a glassy carbon electrode support has been carried out at constant potential and the charge of electrodeposited Ni controlled so as to investigate the effect of precursor Ni layer thickness on the electrocatalytic activity of the corresponding IrO2/Ir(Ni)/GC electrodes for the oxygen evolution reaction (OER). After their preparation, these electrodes were characterized by microscopic (SEM) and spectroscopic (EDS, XPS) techniques, revealing the formation of Ir deposits on the Ni support and a thin IrO2 layer on their surfaces. To determine the electroactive surface area of the IrO2 coatings, cyclic voltammograms were recorded in the potential range between hydrogen and oxygen evolution and the charge under the anodic part of the curves, corresponding to Ir surface oxide formation, served as an indicator of the quantity of active IrO2 in the film. The electrocatalytic activity of the coatings for OER was investigated by current–potential curves under steady state conditions, revealing that the catalysts prepared from thinner Ni films exhibited enhanced electrocatalytic performance. Full article
(This article belongs to the Special Issue Electrocatalytic Water Splitting)
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Review

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20 pages, 2276 KiB  
Review
The Reactivity and Stability of Polyoxometalate Water Oxidation Electrocatalysts
by Dandan Gao, Ivan Trentin, Ludwig Schwiedrzik, Leticia González and Carsten Streb
Molecules 2020, 25(1), 157; https://doi.org/10.3390/molecules25010157 - 31 Dec 2019
Cited by 55 | Viewed by 8035
Abstract
This review describes major advances in the use of functionalized molecular metal oxides (polyoxometalates, POMs) as water oxidation catalysts under electrochemical conditions. The fundamentals of POM-based water oxidation are described, together with a brief overview of general approaches to designing POM water oxidation [...] Read more.
This review describes major advances in the use of functionalized molecular metal oxides (polyoxometalates, POMs) as water oxidation catalysts under electrochemical conditions. The fundamentals of POM-based water oxidation are described, together with a brief overview of general approaches to designing POM water oxidation catalysts. Next, the use of POMs for homogeneous, solution-phase water oxidation is described together with a summary of theoretical studies shedding light on the POM-WOC mechanism. This is followed by a discussion of heterogenization of POMs on electrically conductive substrates for technologically more relevant application studies. The stability of POM water oxidation catalysts is discussed, using select examples where detailed data is already available. The review finishes with an outlook on future perspectives and emerging themes in electrocatalytic polyoxometalate-based water oxidation research. Full article
(This article belongs to the Special Issue Electrocatalytic Water Splitting)
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