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Water electrolysis using renewable energy sources such as solar and wind power has the advantage of producing hydrogen with high efficiency and zero emissions. Solid polymer electrolyte water electrolysis (SPEWE) is divided into anion exchange membrane electrolysis (AEMWE) carried out in an alkaline environment and proton exchange membrane electrolysis (PEMWE) carried out in an acidic environment. Research on the electrocatalysts used in these electrolysis procedures has focused on the development of transition metal-based catalysts with catalytic activity, high stability, and low cost that can replace the currently used noble-metal based electrocatalysts. Among the various electrocatalyst fabrication methods, electrodeposition can be used to fabricate catalysts in a simple manner at low cost and high purity. In addition, catalysts can be directly electrodeposited onto a substrate such as a gas diffusion layer, simplifying the electrode fabrication process and readily enabling the advantageous control of the physical, chemical, structural, and compositional properties of the catalyst. In this paper, we summarize the characteristics and structures of the water electrolysis catalysts prepared by the electrodeposition method based on recent research studies that suggest their applicability to practical water electrolysis systems in the future. [ABSTRACT FROM AUTHOR]

Pt electrocatalysts in high-temperature proton exchange membrane fuel cells (HT-PEMFCs) containing phosphoric acid (PA)-doped polymer membranes are prone to poisoning by leaked PA. We performed a preliminary density functional theory (DFT) study to investigate the relationship between the electronic structure of Pt surfaces and their adsorption of PA. Excess charge on Pt was found to weaken its bonding with the oxygen in PA, thus presenting a strategy for the fabrication of PA-resistant catalyst materials. Consequently, PtCu-alloy catalysts with various compositions were prepared by electrodeposition. The morphologies and crystalline structures of the alloys were strongly dependent on alloy composition. Moreover, the Pt atoms in the PtCu-alloy catalysts were found to be in an electron-rich state, similar to that of the excessively charged Pt simulated in the DFT study. As a result, the oxygen reduction reaction activities of the PtCu-alloy catalysts were superior to that of a Pt-only catalyst, regardless of the presence of PA. In the absence of PA, the higher activity of the PtCu-alloy catalysts was ascribable to conventional alloying effects, while the increased activity in the presence of PA was largely due to the enhanced resistance to PA poisoning. Therefore, PtCu-alloy catalysts easily prepared by electrodeposition were found to be strong candidate materials for HT-PEMFC electrodes. [ABSTRACT FROM AUTHOR]