Unveiling the mechanism of enhanced alkaline hydrogen evolution kinetics on molybdenum–cobalt sulfides for efficient anion exchange membrane water electrolyzers†

Abstract

The rational design of highly efficient and stable electrocatalysts for the alkaline hydrogen evolution reaction (HER) for anion exchange membrane water electrolyzers (AEMWEs) is urgently needed but remains quite challenging. Herein, we develop a core–shell-structured MoS₂/CoS heterostructure (MCS-1) with an optimized shell thickness (60 nm) to address this challenge. Experimental and density functional theory (DFT) calculations disclose that the introduction of CoS into MoS₂ can not only promote the initial H₂O adsorption/dissociation process and optimize the Gibbs free energy of hydrogen adsorption (ΔG_H*) but also induce the fast transfer of the adsorbed hydroxyl, thus avoiding the blocking and poisoning of active sites. Accordingly, MCS-1 exhibits a remarkably enhanced HER performance with lower overpotentials of 64 and 149 mV at 10 and 100 mA cm⁻², respectively. More importantly, using MCS-1 as the cathode and anode to assemble an AEMWE device, we achieved a current density of 200 mA cm⁻² at a low voltage of 1.63 V and stable operation over 500 h in alkaline media. This work provides a new perspective on designing highly efficient and stable alkaline HER catalysts for AEMWEs.