Atomically Confined Ru Sites in Octahedral Co₃O₄ for High-Efficiency Hydrazine Oxidation

Hydrazine-assisted water electrolyzer is a promising energy-efficient alternative to conventional water electrolyzer, offering an appealing path for sustainable hydrogen (H ₂) production with reduced energy consumption. However, such electrolyzer is presently impeded by lacking an efficient catalyst to accelerate the kinetics of pivotal half-reaction, that is, hydrazine oxidation reaction (HzOR). Herein, a ruthenium (Ru) single-atom on an octahedral cobalt oxide (Co ₃O ₄) substrate (Ru-Co ₃O ₄) catalyst, guided by theoretical calculations is developed. Those lattice-confined Ru sites within octahedral structure of spinel Co ₃O ₄ effectively lower the energy barrier required for the formation of N ₂H ₂ ^* intermediate and desorption of H ^* species in HzOR. As a result, the Ru-Co ₃O ₄ catalyst achieves superior HzOR performance with a low potential of −0.024 V versus (vs.)reversible hydrogen electrode (RHE) at 100 mA cm ⁻² and remarkable stability for over 200 h at 200 mA cm ⁻². Importantly, a modular H ₂ production achieves an output of 0.48 kWh electricity per m ³ H ₂ by decoupling and pairing the HzOR and hydrogen evolution reaction (HER) half-reaction with a Zinc (Zn) redox reservoir. The work represents a significant advancement in the field, offering substantial flexibility for on-demand H ₂ production and energy output.