Carbon-encapsulated multi-phase nanocomposite of W 2 C@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 W2 C@WC1-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 WC1-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 WC1-x to W2 C 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 W2 C 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 /ηi value of 1.03 (ηi : 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.