Recent progress of advanced electrocatalysts for hydrogen production via hydrazine-assisted water electrolysis

Coupling the thermodynamically favorable hydrazine oxidation reaction (HzOR) with the hydrogen evolution reaction (HER) in a hybrid water electrolyzer is an effective strategy to improve the energy efficiency of large-scale high-purity H-2 production, while achieving pollutant degradation. Recently, various advanced materials have been exploited as electrocatalysts for hydrazine-assisted water electrolysis, but a fundamental understanding of them and a comprehensive summary are lacking to date. In this review, we provide a comprehensive review of advanced electrocatalysts available for HzOR-assisted water electrolysis, as well as various regulatory strategies based on precious metals and non-noble metal-based materials, such as doping, heterostructures, single-atoms, and alloying. Moreover, the structure-activity relationship including electronic structure, surface properties, and catalytic performance of the electrocatalysts is systematically discussed. Given the importance and unique advantages of direct hydrazine hydrate-assisted seawater electrolysis and self-powered electrolyzers, we also present systematic summaries of material design, performance evaluation, and mechanism studies. Finally, several key challenges and future perspectives about hydrazine-assisted water electrolysis are discussed to offer insight into large-scale H2 production for energy-saving pathways.