Ultrafine cable-like WC/W2C heterojunction nanowires covered by graphitic carbon towards highly efficient electrocatalytic hydrogen evolution

Abstract

Developing highly active, durable and economical noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) plays a crucial role in the future hydrogen economy. Herein, ultrafine cable-like WC/W₂C heterojunction nanowires (NWs) covered by few-layer N-doped graphite-like carbon (labeled WC/W₂C@C NWs) have been firstly accomplished via a simple two-step pyrolysis treatment of W₁₈O₄₉ NWs precursor, exhibiting tunable phase composition, excellent HER activity, fast kinetic metrics and remarkable stability along the entire pH range. With the optimized phase composition, WC/W₂C@C NWs (WC : W₂C ≈ 1 : 1.3) display the low overpotentials of 69 mV and 56 mV at the cathodic current density of 10 mA cm⁻² and small Tafel slopes of 52 and 59 mV dec⁻¹ in 0.5 M H₂SO₄ and 1 M KOH, respectively. DFT calculations and experimental results demonstrate that such prominent performance towards the HER was mainly attributed to abundant interfaces between WC and W₂C phases in the cable-like heterojunction nanowires which may exert both the high HER activity of W₂C and the excellent electrochemical stability and conductivity of WC. Furthermore, the one-dimensional (1D) nanowire morphology and graphite-like carbon shells also promote the conductivity of the whole electrocatalytic material. This work presents a new route to accomplish the morphology control, composition and electronic regulation so as to boost the HER performance of tungsten-carbide-based electrocatalysts, providing new guidance for exploring efficient noble-metal-free electrocatalysts.