Orbital Modulation with P Doping Improves Acid and Alkaline Hydrogen Evolution Reaction of MoS 2 .

There has been great interest in developing and designing economical, stable and highly active electrocatalysts for the hydrogen evolution reaction (HER) via water splitting in an aqueous solution at different pH values. Transition-metal dichalcogenides (TMDCs), e.g., MoS 2 , are identified to be promising catalysts for the HER due to the limited active sites at their edges, while the large basal plane of MoS 2 is inert and shows poor performance in electrocatalytic hydrogen production. We theoretically propose orbital modulation to improve the HER performance of the basal plane of MoS 2 through non-metal P doping. The substitutional doping of P provides empty 3 p z orbitals, perpendicular to the basal plane, can enhance the hydrogen adsorption for acid HER and can promote water dissociation for alkaline HER, which creates significant active sites and enhances the electronic conductivity as well. In addition, 3P-doped MoS 2 exhibits excellent HER catalytic activity with ideal free energy at acid media and low reaction-barrier energy in alkaline media. Thus, the doping of P could significantly boost the HER activity of MoS 2 in such conditions. Our study suggests an effective strategy to tune HER catalytic activity of MoS 2 through orbital engineering, which should also be feasible for other TMDC-based electrocatalysts.