Asymmetric Rh–O–Co bridge sites enable superior bifunctional catalysis for hydrazine-assisted hydrogen production

Abstract

Hydrazine-assisted water splitting is a promising strategy for energy-efficient hydrogen production, yet challenges remain in developing effective catalysts that can concurrently catalyze both the hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR) in acidic media. Herein, we report an effective bifunctional catalyst consisting of Rh clusters anchored on Co₃O₄ branched nanosheets (Rh-Co₃O₄ BNSs) synthesized via an innovative arginine-induced strategy. The Rh-Co₃O₄ BNSs exhibit unique Rh–O–Co interfacial sites that facilitate charge redistribution between Rh clusters and the Co₃O₄ substrate, thereby optimizing their valence electronic structures. When the current density reaches 10 mA cm⁻², the Rh-Co₃O₄ BNSs require working potentials of only 32 mV for the HER and 0.26 V for the HzOR, far surpassing commercial Pt/C. Furthermore, the Rh-Co₃O₄ BNSs can work efficiently for hydrazine-assisted water electrolysis with a low voltage of 0.34 V at 10 mA cm⁻² and excellent stability. Theoretical calculations reveal that the optimized valence electronic structure within interfacial Rh–O–Co sites not only reduces the adsorption energy barrier of Co₃O₄ for H* in the HER; but also optimizes the hydrazine adsorption in the HzOR and lowers the free energy change in the potential-determining step, where the facilitated dehydrogenation is observed in in situ Raman spectra. This work provides a viable approach for designing efficient bifunctional catalysts for future hydrazine-assisted hydrogen production.