Atomic Cluster Outperforms Single Atom in Hydrogen Evolution and Hydrazine Oxidation for Energy‐Efficient Water Splitting

Abstract

The hydrazine‐assisted water splitting (HzAWS) is promising for energy‐saving hydrogen production. However, developing efficient bifunctional catalysts that exert hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR) at industrial‐grade current densities remains challenging. Here, Ru_C‐NiCoP catalyst, ruthenium clusters (Ru_C) immobilized onto NiCoP, is developed to elucidate the superior performance of Ru_C in enhancing bifunctional electrocatalytic activity over ruthenium single atoms (Ru_SA). The Ru_C‐NiCoP achieves current densities of 10 and 100 mA cm⁻² for HER and HzOR with working potentials of −10 and −89 mV, respectively, outperforming Ru_SA‐NiCoP (−16 and −65 mV). During HzAWS, a cell voltage reduction of 1.77 V at 300 mA cm⁻² is observed compared to overall water splitting. Density functional theory calculations reveal that Ru_C improves the adsorption energy for H₂O and N₂H₄, optimizes the H* intermediate desorption, and reduces the dehydrogenation barrier from *N₂H₃ to *N₂H₂. Additionally, the direct hydrazine fuel cell with a Ru_C‐NiCoP anode delivers an impressive power density of 226 mW cm⁻² and enables a self‐powered hydrogen production system, achieving an unprecedented hydrogen production rate of 4.9 mmol cm⁻² h⁻¹. This work offers a new perspective on developing efficient sub‐nanoscale bifunctional electrocatalysts and advancing practical energy‐saving hydrogen production techniques.