Accelerating H* desorption of hollow Mo2C nanoreactor via in-situ grown carbon dots for electrocatalytic hydrogen evolution

Molybdenum carbide (Mo2C) is a promising non-noble metal electrocatalyst with electronic structures similar to Pt for hydrogen evolution reaction (HER). However, strong H* adsorption at the Mo sites hinders the improvement of HER performance. Here, we synthesized monodisperse hollow Mo2C nanoreactors, in which the carbon dots (CD) were in situ formed onto the surface of Mo2C through carburization reactions. According to finite element simulation and analysis, the CD@Mo2C possesses better mesoscale diffusion properties than Mo2C alone. The optimized CD@Mo2C nanoreactor demonstrates superior HER performance in alkaline electrolyte with a low overpotential of 57 mV at 10 mA cm−2, which is better than most Mo2C-based electrocatalysts. Moreover, CD@Mo2C exhibits excellent electrochemical stability during 240 h, confirmed by operando Raman and X-ray diffraction (XRD). Density functional theory (DFT) calculations show that carbon dots cause the d-band center of CD@Mo2C to shift away from Fermi level, promoting water dissociation and the desorption of H*. This study provides a reasonable strategy towards high-activity Mo-based HER eletrocatalysts by modulating the strength of Mo–H bonds.