Carbon-encapsulated multi-phase nanocomposite of W₂C@WC_{1-: X} as a highly active and stable electrocatalyst for hydrogen generation

The major challenges related to the activity, stability, and cost of electrocatalysts are being increasingly raised to achieve highly efficient and cost-effective hydrogen generation. Herein, multiphase nanocomposites of W₂C@WC_1-x encapsulated within graphitic carbon layers were prepared via a facile and effective process of electrical explosion of wires and subsequent heat treatment to serve as a highly active and stable electrocatalyst without any noble metal for hydrogen generation. The single-phase comprising less than 15 nm WC_1-x nanoparticles embedded in a lump of amorphous carbon were successfully synthesized via the EEW process in oleic acid used as a carbon source at room temperature. Subsequent heat treatment facilitates the desired phase transition of WC_1-x to W₂C without the formation of any secondary phases, maintaining the initial particle size and simultaneously eliminating excess amorphous carbon adhered to the nanoparticles. The few graphitic carbon layer-encapsulated nanoparticles with the main W₂C phase prepared by this simple method exhibit high efficiency for hydrogen generation with a low overpotential of 240 mV at a current density of 10 mA cm^-2 and a low Tafel slope of 86 mV dec^-1. Moreover, the overpotential is well maintained at a constantly injected current density of 10 mA cm^-2 for 100 h with a low η₁₀₀/η_i value of 1.03 (η_i: initial overpotential, η₁₀₀: overpotential after 100 h), demonstrating superior catalytic stability in acidic media. This work proposes and evaluates a facile strategy for the synthesis of highly efficient electrocatalysts based on metal carbides without noble metals.