Catalytic hydrogen production by isoelectronic doped MoS₂

In recent years MoS₂ has been widely investigated as a prospective catalyst for hydrogen production. Although MoS₂ is inferior to Pt, there are plenty of ways for its modification. Manipulation with phases, amount of vacancies, edges, and grain boundaries path the way to make MoS₂ a superior material for electrocatalytic H₂ production. However, controlling all these parameters during the synthesis is still problematic. We claim that the isoelectronic doping during chemical vapor deposition of MoS₂ may be an effective way to control these changes desirably.

This work reveals the doping of MoS₂ monolayers by isoelectronic atoms (W and Se) in broad concentration range effects on the catalytic activity. At low concentrations (up to 30%), both dopants significantly decrease the Tafel slopes, which indicates the increasing effectivity of H₂ formation. However, hydrogen formation is inhibited at high defect concentrations (35-50%). At lower doping rates, single atom defects trigger the formation of vacancies, the transition of 2H into the metastable 1T phase, and phase boundaries occurrence. These factors strongly tune up the hydrogen adsorption on the doped MoS₂ surface. As the doping rate achieves 35%, defects coagulate into the pure 2H phase MoS₂, WS₂, and MoSe₂, which inhibit the reaction.