Recent Advances in Hydrogen Production from Hybrid Water Electrolysis through Alternative Oxidation Reactions

Water splitting driven by green electricity from renewable energy input to produce H2 has been widely considered as a promising strategy to realize the goals for future clean energy. However, in conventional overall water electrolysis, the sluggish kinetics and high onset potential of anode OER limit the cathode HER rate, which lowers the overall energy conversion efficiency. Over the past decade, an innovative concept involving hybrid water electrolysis by replacing OER with thermodynamically more favorable oxidation reactions coupling with the cathodic hydrogen evolution reaction has been devised to alleviate the limitations associated with the anodic OER. In this review, we summarize the recent progress concerning electrochemical hydrogen production by coupling the oxidation of molecules incorporating hydroxyl, aldehyde, and amino functional groups, with special emphasis on alternative reactions involving CO and sulfide. Finally, the remaining challenges and future perspectives are also discussed. We hope this review will accelerate the development of novel strategies for practicable H2 production from hybrid water electrolysis. In this review, we provide comprehensive overview of potential anodic oxidation systems that can replace OER, focusing on hybrid electrolysis of water. The advantages, challenges and outlooks of using alcohols and aldehydes, biomass derived compounds, amines, and other small molecules as anodes alternative reactants for electrolytic hydrogen production have been discussed in detail.