VS<sub>2</sub> Nanoflowers\nSupported on Ti<sub>3</sub>C<sub>2</sub> MXene as Electrocatalyst\nfor the Hydrogen Evolution\nReaction

Under the threat of the two major dilemmas of energy\nscarcity and\nenvironmental degradation, the development of sustainable, clean,\nand efficient energy sources has become increasingly urgent. In recent\nyears, electrocatalytic hydrogen evolution reaction (HER) has become\na promising method for the preparation of energy sources for sustainable\nhydrogen production. However, the monolithic nature of the active\nsite/active phase of metallic transition metal disulfides (MTMDs)\nlimits the performance of HER to that of commercial Pt/C catalysts.\nHerein, we report the hydrothermal growth of VS<sub>2</sub>/Ti<sub>3</sub>C<sub>2</sub> heterogeneous structure on MXene substrates\nfor the first time. The VS<sub>2</sub>/Ti<sub>3</sub>C<sub>2</sub> heterogeneous structure exhibits extremely high catalytic activity\nand electrochemical durability. Exhibiting an overpotential of only\n33 mV and a Tafel slope of 25.93 mV dec<sup>–1</sup> in 0.5\nM H<sub>2</sub>SO<sub>4</sub> acidic electrolyte, the catalysts showed\nexcellent durability over 24 h and near 100% Faraday efficiency. Meanwhile,\nthe formation of heterogeneous structure was also demonstrated by\nboth X-ray photoelectron spectroscopy (XPS) and transmission electron\nmicroscopy (TEM) data. Theoretical studies confirmed that the successful\nconstruction of Ti–S bonds in VS<sub>2</sub>/Ti<sub>3</sub>C<sub>2</sub> heterogeneous structure accelerates the charge transfer\nrate, which modifies the electrical properties of VS<sub>2</sub> nanoflowers\nand the hydrogen adsorption properties at the Ti-edge and the S-edge.\nThis work accelerated the charge transfer rate of the electrocatalyst\nthrough the formation of a heterogeneous structure between VS<sub>2</sub> and Ti<sub>3</sub>C<sub>2</sub>, providing a strategy for\nhighly efficient electrocatalytic hydrogen evolution reaction.