Grain Boundary-Rich Tungsten Carbide Nanoparticle Films Exhibit High Intrinsic Activity Toward Hydrogen Evolution

Tungsten carbides have an electronic density of states near the Fermi level similar to platinum and are predicted to exhibit high intrinsic activity toward the hydrogen evolution reaction (HER). However, traditional fabrication routes typically require high synthesis temperatures, resulting in undesirable agglomeration and losses in electrocatalytic performance. Herein, we demonstrate the use of thermal spikes, a high-energy transient phenomenon resulting from ion implantation, to synthesize tungsten carbide nanoparticle films without thermal annealing. By precisely controlling the carbon fluence implanted into smooth tungsten thin-film substrates, β-W2C, γ-WC, and δ-WC were selectively synthesized. Despite their low surface area, the tungsten carbide films possessed a high density of grain boundaries resulting in excellent intrinsic HER activity and stability (TOF = 11 H2 s-1, 10 mA cm-2 for 12 h). These results confirm that ion implantation is a promising approach for synthesizing tungsten carbide nanoparticle films with high intrinsic activity toward HER.