Carbon-encapsulated multi-phase nanocomposite of W2C@WC1−x as a highly active and stable electrocatalyst for hydrogen generation

Abstract

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.