Critical Role of Interface Design in Acceleration of Overall Water Splitting and Hybrid Electrolysis Process: State of the Art and Perspectives

Electrocatalytic water splitting to hydrogen (H<inf>2</inf>) is an ideal approach to generate renewable energy. One of the major drawbacks is the tightly coupled kinetically sluggish and energy inefficient anodic oxygen evolution reaction (OER) with hydrogen forming a cathodic half-cell reaction which leads to a significant reduction in overall cell efficiency. In this context, before reviewing the literature, we have first briefly analyzed the energetics of overall water splitting, problems, and challenges under different pH conditions which can be useful for the further understanding of the process. Replacement of the anodic OER by a thermodynamically favorable substrate oxidation offers flexibility, value addition, and energy efficiency in the case of hybrid or assisted water electrolysis to afford hydrogen. Recent progress in terms of sacrificial oxidants in hybrid water electrolysis are discussed in this context, where the sacrificial oxidants are so chosen that the oxidation often leads to its value addition. Also here, we have offered insights into interface designing in heterostructures by modulating chemical and electronic environments for the enhancement of the intrinsic catalytic activity and stability. The effect of incorporation of such materials into the overall water splitting reaction, their catalytic active sites, and interactions with intermediates are thoroughly explored. This review can be a good complement for better understanding of the elucidation of the interface role in hybrid water electrolysis for future commercial applications.