Vanadium carbide nanodots anchored on N doped carbon nanosheets fabricated by spatially confined synthesis as a high-efficient electrocatalyst for hydrogen evolution reaction

Creating more active sites is an ideal strategy to enhance a catalyst's performance in which the trigger needs a nanosized or micro-grained structure. However, it suffers inevitable aggregation during the fabrication process resulting in the low hydrogen evolution reaction (HER) activity. Herein, vanadium carbide nanodots with 7.5 nm in size anchored on N doped carbon nanosheets (VC/NC) are synthesized by magnesiothermic reduction (MTR) using hybrid vanadium pentoxide (V₂O₅)/polyaniline composite as the precursor. During MTR, the V₂O₅ species in situ convert into VC nanodots, and the polyaniline layers translate into NC nanosheets. Owing to the highly conductive and stable NC nanosheets and abundance of active sites on VC nanodots, the VC/NC delivers a small overpotential of 76 mV at a current density of 10 mA cm⁻² with Tafel slope of 46 mV dec⁻¹ and excellent stability in 0.5 M H₂SO₄. The X-ray Photo-electronic Spectroscopy (XPS) and density functional theory (DFT) calculations reveal that the charge transfers from NC to VC, causing moderate H binding energy. This novel concept can be extended to prepare ultrafine metal oxides, carbides, and nitrides nanodots.