Ditungsten carbide nanoparticles encapsulated by ultrathin graphitic layers with excellent hydrogen-evolution electrocatalytic properties

The development of efficient non-precious-metal electrocatalysts towards the hydrogen evolution reaction (HER), with superior activity and stability, remains a great challenge in the area of renewable energy. In this work, we demonstrated a facile, one-step protocol to synthesize ultrathin graphitic layer (GL)-encapsulated ultrafine ditungsten carbide (W₂C) nanoparticles (W₂C@GL) with sizes smaller than 10 nm, exhibiting a superior HER activity in acidic solution. An efficient W₂C phase, along with an improved electron transfer process by GL wrapping, cooperatively leads to a small Tafel slope of 68 mV dec^-1 and a large exchange current density of 0.24 mA cm^-2 for W₂C@GL, which exceeds the previous W₂C materials by far. Over 91% of the current density is maintained after over 8 h of operation, which indicates a good stability of this hybrid catalyst. Thus, W₂C@GL with these excellent properties has been among the best non-noble metal HER electrocatalyst reported to date.