Mesoporous Co-MoS2 with sulfur vacancies: A bifunctional electrocatalyst for enhanced water-splitting reactions in alkaline media

Abstract

As a graphene-like layered material, molybdenum disulfide (MoS₂), has attracted increasing attentions for its promising application in electrocatalysis. Whereas MoS₂ still suffers from the sluggish reaction kinetics in oxygen evolution reaction (OER) due to the low density of active sites in most exposed planes. In this work, high density of active sites on MoS₂ basal planes has been obtained by synthesizing mesoporous MoS₂ with Co doping and sulfur vacancies (V_S). The synergy of the mesoporous structure, Co doping, and sulfur vacancies resulted in optimized bifunctional electrocatalytic activity for both hydrogen evolution reaction (HER) and OER in alkaline media. The overpotential required to achieve a current density of 10 mA cm⁻² (denoted as η₁₀) is 34 mV for HER and 268 mV for OER, respectively. The two-electrode electrolyzer constructed with the as-prepared cobalt-doped mesoporous MoS₂ electrodes exhibited a low bias (η₁₀ = 1.58 V) for overall water splitting. Density functional theory (DFT) calculations confirm the significance of Co doping and the S vacancy defects, which lowers the Gibbs free energy (ΔG) for the formation of the corresponding intermediates.