Single-Step Synthesis of W2C Nanoparticle-Dispersed Carbon Electrocatalysts for Hydrogen Evolution Reactions Utilizing Phosphate Groups on Carbon Edge Sites

A novel, one-step protocol for the selective synthesis of W 2 C nanoparticles from phosphotungstic acid (H 3 PW 12 O 40 ), a low-cost and commercially available tungsten compound, was developed. The nanoparticles had diameters of 1-50 nm and were dispersed on a carbon substrate. The W 2 C nanoparticles were prepared by a simple operation sequence, involving impregnation of carbon black with H 3 PW 12 O 40 followed by calcination at 1000 °C. X-ray diffraction study revealed the selective formation of the W 2 C phase in the samples prepared, whereas the tungsten carbide (WC) phase was present in the control prepared from H 2 WO 4 . Stable W 2 C nanoparticles were obtained using this method owing to the presence of phosphate at the interfaces between the W 2 C nanoparticles and the carbon substrates, which inhibited the diffusion of carbon atoms from the carbon substrates to the W 2 C nanoparticles, leading to the formation of WC. The W 2 C nanoparticles prepared showed an excellent catalytic activity for the hydrogen evolution reaction (HER), with low Tafel slopes of ∼50 mV/decade. The HER catalytic activity was notably high, being comparable to that of MoS 2 , which is a promising alternative to Pt. The present method can potentially be applied to produce highly effective, low-cost, Pt-free electrocatalysts for the HER.