Controllable Thermochemical Generation of Active Defects in the Horizontal/Vertical MoS₂ for Enhanced Hydrogen Evolution

Abstract As for 2D transition metal dichalcogenides, the creation of proper active defects concentrations is considered as the efficient strategy for improving hydrogen evolution performance. However, the synthesis methods of large‐area MoS₂ catalysts with controllable active defects are limited, also for its working mechanism. Herein, thermochemical generation of active defects for MoS₂ catalysts has established by annealing sodium hypophosphite, in which the phosphine is spontaneously generated and chemically tailors the MoS₂ lattice. The defects formation is confirmed by the investigation of slightly‐changed surface structure and unpaired electrons for the annealed samples. The hydrogen evolution reaction performances of horizontally/vertically grown MoS₂ films are improved by controlling reaction conditions, indicating the active defects could form in the basal plane and edges with retained crystal structure. The overpotential of MoS₂ samples converted from 10 nm Mo reduces from −520 to −265 mV with largely decreased Tafel slope. The electrochemical microreactor studies reveal the protons adsorption of active sites shows much more significant contribution, than interfacial charge transfer with the enhanced remarkable performance (−100 mV at 10 mA cm⁻²). This study presents the large‐area synthesized strategy for MoS₂ based catalysts with controllable defects concentration and helps establish rational design principles for future MoS₂ family electrocatalysts.