Abstract
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.