Earth-Abundant Metal-Based Electrocatalysts Promoted Anodic Reaction in Hybrid Water Electrolysis for Efficient Hydrogen Production: Recent Progress and Perspectives

Exploring advanced technologies to efficiently produce green hydrogen energy is imperative to alleviate the energy crisis and environmental pollution. Conventional overall water electrolysis (OWE) has been regarded as a promising approach for effective H-2 production, however, it is largely restricted by the sluggish kinetics of the anodic oxygen evolution reaction (OER). Coupling kinetically favorable anodic reactions, such as biomass-derived compound oxidation and pollutant degradation, with the hydrogen evolution reaction (HER) in hybrid water electrolysis (HWE), can not only solve the biomass recycling and pollutant emission problems but also save the energy cost for clean H-2 generation. Hence, various advanced earth-abundant electrocatalysts have been developed to catalyze those promising anodic reactions, yet some problems such as tedious preparation and unsatisfactory performance still exist. Given the gap between research and practical applications, this review summarizes the recent progress in electrocatalysts for diverse alternative anodic oxidation reactions over the last five years together with their application in HWE systems. An in-depth understanding of different reaction mechanisms and assessments toward electrocatalysts is discussed to further enhance anodic efficiency. The advantages, differences, and critical issues of different HWE systems are thoroughly discussed as well, providing a new avenue for low-voltage H-2 production from renewable resources and waste products.