Hybrid water electrolysis as the way forward to sustainable hydrogen production

Replacing the anodic oxygen evolution reaction (OER) with energy saving and more favorable electrochemical oxidation reactions opens a new door to an innovative way for sustainable hydrogen production. Specifically, the electro-oxidation of organic compounds, biomass molecules, and plastic waste has attracted tremendous interest in recent years owing to its potential for H2 production at the cathode chamber and production of value-added chemicals and fuels at the anode chamber. This review is not intended to provide an in-depth, comprehensive overview of all these reactions and hybrid water electrolysis but rather highlight the key aspects of hybrid water electrolysis. The basic understanding of hybrid water electrolysis, its advantages over conventional water electrolysis, major reactions, bifunctional electrocatalysts and their fabrication based on the available information are discussed. Although this review sheds light on the basic understanding of alternative oxidation reactions in hybrid water electrolysis, a special focus is given on the important question of whether the bifunctional electrocatalysts employed in conventional water electrolysis will be effective in hybrid water electrolysis. Lastly, the challenges and perspectives are discussed.