Energy-saving electrochemical hydrogen production via co-generative strategies in hybrid water electrolysis: Recent advances and perspectives

Traditional overall water splitting has been regarded as a potential pathway for H2 production, but the intrinsic slow kinetics of the anodic oxygen evolution reaction severely hampers the efficiency of H2 production. Given the challenges in traditional water electrolysis, coupling the kinetically favorable anodic electrooxidation reactions of easily oxidizable substances with the hydrogen evolution reaction in a hybrid water electrolysis (HWE) configuration not only solves the pollutant emission and biomass recycling problems but also maximizes the return on energy profiteering. Various advanced compounds have been engineered through compositional regulation, structural optimization, surface nano-building, and electronic structure modification, yet some issues like tedious preparation and unsatisfactory durability still exist. Considering the gap between research and practical deployment, this review amply addresses the state-of-the-art achievements of synergistic electrocatalysis systems for the co-production of high-purity H2 and valuable products with a low energy consumption and high Faradaic efficiency. An overview of HWE system is presented first accompanied by a discussion on the design and engineering of high reactive/selective/stable electrodes/electrocatalysts for anodic oxidation of organic/biomass substrates. Importantly, the in-depth understanding of possible reaction mechanisms from both experimental and theoretical perspectives is elucidated to promote the efficiency of synergistic electrocatalysis. Subsequently, the recent research breakthroughs in the field of HWE technology are emphatically reviewed, providing a new room for low-voltage H2 generation from waste products and renewable feedstock. Some mechanism explorations, feasibility analyses, and correlation comparisons are highlighted. Finally, we propose the prospects on existing challenges with some opportunities for future research directions to push forward the progress in synergistic electrocatalysis configurations.