H2 Regulates the Sulfur Vacancy of Mo-Doped WS2 for Electrochemical Hydrogen Evolution Reaction

The development of efficient and economical nonprecious metal electrocatalysts is crucial for advancing the industrialization of the hydrogen evolution reaction (HER) in water electrolysis. WS₂ has become a hotspot in HER research due to its unique physicochemical properties and potential applications. In this work, a series of Mo-WS₂-n (n = 0, 0.3, 0.5 and 1.0, representing H₂ pressure) samples with abundant sulfur vacancies were prepared by utilizing H₂ as the structure directing agent (SDA). Among them, the Mo-WS₂-0.5 sample possessing abundant sulfur vacancies demonstrated best acidic HER performance by displaying an overpotential of 146 mV at 10 mA cm^–2 and the Tafel slope of 46.8 mV dec^–1, which is superior to most reported WS₂-based electrocatalysts. Furthermore, Mo-WS₂-0.5 exhibits good stability, proving its potential in practical applications. During the synthesis process, H₂ can effectively remove S atoms from WS₂ to create sulfur vacancies. Theoretical calculations unravel that both Mo doping and sulfur vacancies can significantly reduce the Gibbs free energy of hydrogen atom adsorption (ΔG_H) of WS₂. This study not only offers new insights into understanding the effects of metal doping and sulfur vacancies in WS₂ on acidic HER, but also provides a practical approach for designing low-cost and high-performance non-noble metal electrocatalysts.