Hydrogen and value-added products yield from hybrid water electrolysis: A critical review on recent developments

Water electrolysis is considered a promising approach for ultrapure hydrogen production. However, the conventional water electrolysis method suffers from high overpotential, mainly due to sluggish reaction kinetics of oxygen evolution reaction (OER). The reactive oxygen species are generated by OER, which degrades the proton exchange membrane, and oxygen can combine with cathodic hydrogen to form explosive gaseous mixtures. Over the past decade, researchers have been exploring the hybrid water electrolysis method by replacing OER with an alternative oxidation reaction. In the hybrid water electrolysis method, oxidizing the chemical agent assists electrochemical hydrogen production at an ultra-low potential, which in particular, forms value-added products. The hybrid water electrolysis technique uses electrocatalysts to drive the chemical species-assisted hydrogen production. This review summarizes the recent development of electrochemical hydrogen production through the hybrid water electrolysis method and fundamental knowledge of reaction mechanisms. In addition, the design methods of noble metal, non-noble metal, and carbon-based electrocatalysts were investigated. Further, the review discusses the probable anodic reactions to replace OER and various oxidative products for efficient H2 production and generation of value-added products. Finally, the current challenges and perspectives for the future development of hybrid water electrolysis technologies are discussed.