Transition-metal-based electrocatalysts for hydrazine-assisted hydrogen production

Electrocatalytic water splitting is considered as the next-generation strategy for large-scale ultrapure hydrogen production. However, the high thermodynamic potential (1.23 V vs. the reversible hydrogen electrode) and slow kinetics of the anodic oxygen evolution reaction (OER) restrict the wide application of electrocatalytic water splitting. Replacing OER by hydrazine oxidation reaction (HzOR) with lower oxidizing potential can effectively increase the energy efficiency and save the cost of production. Thus, for the hydrazine-assisted electrolytic hydrogen production, transition-metal-based (TM-based) materials are developed to work as efficient electrocatalysts, due to the facile tuning of their physicochemical properties and their low costs. In this review, we summarize the latest advances on the TM-based catalysts for hydrazine-assisted hydrogen production, with focus on the catalytic properties and mechanisms. Moreover, several key issues of the hydrogen production process and perspectives are discussed to give insight into the foundation for the future development of hydrazine-assisted electrolytic hydrogen production.