Dual-independent active sites for efficient hydrogen production

Abstract

Redox bifunctional electrocatalysts play a significant role in driving electrochemical cells, which is hardly achieved by a single active site due to the totally different catalytic reaction mechanism. Herein, we propose dual-independent active sites as a proof-of-concept to design Mo₂C@C/Co@C bifunctional catalysts for efficient hydrogen production, where carbon coated Mo₂C nanoparticles (Mo₂C@C) serve as desirable hydrogen evolution reaction (HER) active sites, while Co encapsulated in carbon layers (Co@C) provides favorable active sites for the hydrazine oxidation reaction (HzOR). During the thermal reorganization, Mo₂C and Co can be self-assembled from the precursor into dispersed and uniform nanoparticles to construct dual-independent active sites with a tightly contacted hierarchical structure, beneficial for bifunctional properties, with low overpotentials of −83 mV and 71 mV to reach 10 mA cm⁻² for the HzOR and HER, respectively. When applied in symmetric OHzS, the electrolyzer requires 0.49 V to achieve 300 mA cm⁻². The Mo₂C@C/Co@C assembled Zn–Hz battery exhibits excellent durability for 300 cycles with an energy efficiency of 94%.