Oxygen-Doped VS4 Microspheres with Abundant Sulfur Vacancies as a Superior Electrocatalyst for the Hydrogen Evolution Reaction

In this work, one-dimensional chainlike structured vanadium tetrasulfide (VS4) with rich defects has been demonstrated as an advanced electrocatalyst for an efficient hydrogen evolution reaction (HER). The VS4 microspheres featuring oxygen doping and abundant sulfur vacancies are synthesized by a simple solution method. The O-doping and S-vacancy offer the VS4 with a dramatically narrowed band gap and an improved intrinsic electronic conductivity, benefitting for fast charge transport during the HER process. Furthermore, the rich defects of sulfur vacancies and oxygen heteroatoms provide more active sites with high activity for catalyzing protons to hydrogen reaction. Owing to the synergistic effects of defect engineering and electronic benefits, the VS4 microspheres serve as a superior HER catalyst surpassing the 1T-VS2 microflowers with a layered structure. The VS4 microsphere catalyst exhibits prominent kinetic metrics of a low onset potential of 15 mV, a low overpotential of 48 mV at 10 mA cm(-2), a small Tafel slope of 44 mV dec(-1), and a stable long-term operation of 75 h. This work paves a new pathway to improve the electrocatalytic activity of HER catalysts by synergistically modulating their defects and electronic structures.