Phosphorus-doped MoS2 with sulfur vacancy defects for enhanced electrochemical water splitting

MoS2 is a promising electrocatalyst because of its natural abundance and outstanding electrochemical stability. However, the poor conductivity and low activity limit its catalytic performance; furthermore, MoS2 is unable to satisfy the requirements of most industrial applications. In this study, to obtain a P-doped MoS2 catalyst with S vacancy defects, P is inserted into the MoS2 matrix via a solid phase ion exchange at room temperature. The optimal P-doping amount is 11.4 wt%, and the resultant catalyst delivers excellent electrocatalytic properties for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with the corresponding overpotentials of 93 and 316 mV at 10 mA cm−2 in an alkaline solution; these values surpass the overpotentials of most previously reported MoS2-based materials. Theoretical calculations and results demonstrate that the synergistic effect of the doped P, which forms active centers in the basal plane of MoS2, and S vacancy defects caused by P doping intensifies the intrinsic electronic conductivity and electrocatalytic activity of the catalyst. Density functional theory calculations demonstrate that P optimizes the free energy of the MoS2 matrix for hydrogen adsorption, thereby considerably increasing the intrinsic activity of the doped catalyst for the HER compared with that observed from pristine MoS2. The enhanced catalytic activity of P-doped MoS2 for the OER is attributed to the ability of the doped P which facilitates the adsorption of hydroxyl and hydroperoxy intermediates and reduces the reaction energy barrier. This study provides a new environmentally friendly and convenient solid-phase ion exchange method to improve the electrocatalytic capability of two-dimensional transition-metal dichalcogenides in large-scale applications.