Abstract
This review paper presents the most recent research progress on carbon-based composite electrocatalysts for the oxygen evolution reaction (OER), which are of interest for application in low temperature water electrolyzers for hydrogen production. The reviewed materials are primarily investigated as active and stable replacements aimed at lowering the cost of the metal electrocatalysts in liquid alkaline electrolyzers as well as potential electrocatalysts for an emerging technology like alkaline exchange membrane (AEM) electrolyzers. Low temperature electrolyzer technologies are first briefly introduced and the challenges thereof are presented. The non-carbon electrocatalysts are briefly overviewed, with an emphasis on the modes of action of different active phases. The main part of the review focuses on the role of carbon–metal compound active phase interfaces with an emphasis on the synergistic and additive effects. The procedures of carbon oxidative pretreatment and an overview of metal-free carbon catalysts for OER are presented. Then, the successful synthesis protocols of composite materials are presented with a discussion on the specific catalytic activity of carbon composites with metal hydroxides/oxyhydroxides/oxides, chalcogenides, nitrides and phosphides. Finally, a summary and outlook on carbon-based composites for low temperature water electrolysis are presented.
Highlights
Another type involves an in situ formation of the active phase overlayer, especially from materials unstable under reaction conditions, as in β-NiO(OH)/Ni2 P@NiO catalyst supported on Mg2 O(OH)2 -like phase, which is formed during the oxygen evolution reaction, where the Ni2 P nanoparticles are immediately oxidized forming a core–shell structure
The search for active and stable materials for the oxygen evolution reaction has become a field with enormous interest for the development of efficient and cost-effective electrochemical devices like water electrolyzers or aqueous metal–air batteries
We provide the most recent investigations on the incorporation of carbon-based composite materials and analyze the most relevant advances in activity and stability issues
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Water electrolysis using renewable energy sources and water as a substrate may be an answer to the problem of sustainable hydrogen production It is a fascinating subject for studies from the fundamental point of view as the reaction itself is very complex, as are the reaction conditions. From the mechanistic point of view, the most popular proposed reaction schemes involve the coupling of electron and proton transfer in every step If this coupling was always present in the oxygen evolution reaction pathway, it would put severe limitations on the optimization of the catalysts. Oxygen evolution is an important reaction in the water electrolysis application, and in reversible fuel cells, and metal–air batteries, and it is anticipated that OER will play a vital role in the design of efficient energy conversion and storage devices [16]
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