Activating the MoS₂ Basal Plane toward Enhanced Solar Hydrogen Generation via in Situ Photoelectrochemical Control

Developing robust, low-cost, and scalable catalysts for photoelectrochemical (PEC) water splitting devices is crucial for the sustainable hydrogen evolution reaction (HER). MoS2 has emerged as a potent alternative to Pt-based catalysts for the HER. However, the active sites of 2H-MoS2 are reported to locate at the edges, leaving a large number of inert basal planes useless. Herein, a facile strategy is reported to activate the MoS2 basal plane via an in situ PEC protocol. Both experimental studies and theoretical calculations reveal the emergence of O–Mo–S sites on the MoS2 basal planes, which enable not only enhancing its intrinsic conductivity but also modulating the adsorption behavior of H atoms and consequent HER activity. As a result, the MoS2-decorated Si photocathodes exhibit an applied bias photon-to-current efficiency of 4.9% under the simulated AM1.5G illumination. This study offers a potential scalable route for the fabrication of high-performance and precious metal-free solar-to-fuel devices.