Sulfur Vacancy-Induced Enhancement of Piezocatalytic H₂ Production in MoS₂

This study explores the role of S vacancies in MoS₂ in enhancing its piezocatalytic efficiency. Sulfur vacancies in the crystal lattice introduce localized changes in the electronic structure and charge distribution, improving the material's piezoelectric response. Characterization of the catalysts involved techniques like field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements, including impedance spectroscopy (EIS) and Mott-Schottky (M-S) analysis, are performed to assess the piezocatalytic performance. The study also employed density functional theory (DFT) calculations to investigate the electronic structure and hydrogen adsorption properties of MoS₂ with S vacancies. The results demonstrated that S-deficient MoS₂ significantly enhanced piezocatalytic H₂ evolution. The piezocatalytic H₂ production rates of MoS₂ with different vacancy concentrations are measured under ultrasonic vibration. The sample with an optimal vacancy concentration (MS-1) exhibited the highest H₂ production rate of 1423.29 µmol g^-1 h^-1, compared to 439.06 µmol g^-1 h^-1 for pristine MoS₂ (MS-0). The improved performance is attributed to the increased piezoelectric polarization and efficient charge separation facilitated by S vacancies.