Ultrasmall and phase-pure W(2)C nanoparticles for efficient electrocatalytic and photoelectrochemical hydrogen evolution

Earlier research has been primarily focused on WC as one of the most promising earth-abundant electrocatalysts for hydrogen evolution reaction (HER), whereas the other compound in this carbide family—W(2)C—has received far less attention. Our theoretical calculations suggest that such a focus is misplaced and W(2)C is potentially more HER-active than WC. Nevertheless, the preparation of phase pure and sintering-free W(2)C nanostructures represents a formidable challenge. Here we develop an improved carburization method and successfully prepare ultrasmall and phase-pure W(2)C nanoparticles. When evaluated for HER electrocatalysis, W(2)C nanoparticles exhibit a small onset overpotential of 50 mV, a Tafel slope of 45 mV dec(−1) and outstanding long-term cycling stability, which are dramatically improved over all existing WC-based materials. In addition, the integration of W(2)C nanoparticles with p-type Si nanowires enables highly active and sustainable solar-driven hydrogen production. Our results highlight the great potential of this traditionally non-popular material in HER electrocatalysis.