Modulating Electronic Structure of MoS2 Nanosheets by Sulfide Enrichment-Induced Vacancies for Enhanced Photocatalytic Hydrogen Production

Abstract

Enhancing photocatalytic activity by changing the electronic structure of the catalyst is an effective strategy. 2H-MoS₂ has semiconductor properties, and its unsaturated side S atom is the main active site for its photocatalytic activity. However, due to the weak S─H bond energy, its hydrogen adsorption capacity is weak. In this work, the electronic structure of MoS₂ is adjusted by S-rich treatment, resulting in the formation of Mo vacancy (MoS₂-V_Mo). The level of Mo vacancies was assessed using UV–vis diffuse reflectance spectroscopy (UV–vis DRS). As these vacancies can capture certain photogenerated electrons, thereby reducing the recombination of electron-hole pairs. Through DFT calculation, it is found that the antibonding orbital electron filling of MoS₂-V_Mo is weakened, the bond energy of S─Mo bond is weakened, and the bond energy between S─H bond is enhanced, which is more conducive to proton adsorption. The photocatalytic activity for hydrogen evolution of MoS₂-3, which underwent the optimal S-rich treatment, achieved a remarkable rate of 2404.6 µmol g⁻¹ h⁻¹ in dye eosin Y (EY) sensitization system, significantly surpassing that of MoS₂ lacking the S-enriched treatment. This study introduces a novel concept for enhancing the photocatalytic hydrogen evolution performance of metal sulfides via defect engineering.