Single-atom dispersed Cu or Co on 2H-MoS2 monolayer for improving electrocatalytic activity of overall water splitting

Abstract

Low-cost but high-performance electrocatalysts based on free-noble metals for overall water splitting are crucial for the clean energy production. By density functional theory (DFT) calculations, we explored the possibility of using single-atom dispersed Cu or Co on two-dimensional (4 × 4 × 1) 2H-MoS2 monolayer (Cu@2H-MoS2 and Co@2H-MoS2) to activate the inert basal planes of 2H-MoS2 and to realize overall water splitting reaction. Our results reveal that Cu@2H-MoS2 and Co@2H-MoS2 can significantly alter surface charge distribution and electronic band structure of 2H-MoS2, and Gibbs free-energies of adsorbed H and O species on 2H-MoS2. As a result, the incorporation of Cu or Co single atoms can activate inert in-plane S-atoms, and lead to the improved electrochemical activity for both hydrogen and oxygen evolution reactions (HER and OER). Relatively, Co@2H-MoS2 exhibits better performance for HER with smaller Gibbs free energy of the hydrogen adsorption (ΔGH=0.08 eV), which is comparable to (4 × 4 × 1) Pt (111) surface (ΔGH= -0.22 eV). Compared to pristine 2H-MoS2 or Co@2H-MoS2, the catalytic activity of Cu@2H-MoS2 for OER is considerably improved with a reduced overpotential of 1.25 eV and a lower energy barrier. This study provides a design route for constructing high-performance single-atom catalysts for the overall water splitting.