WC/Mo2C heterojunctions modified with Ru embedded on carbon matrix for efficient hydrogen evolution in water electrolysis

Abstract

Tungsten carbide and molybdenum carbide heterojunctions (WC/Mo₂C) modified with trace amounts of Ru (Ru-WC/Mo₂C) embedded on amorphous carbon matrix was prepared by calcination of the metal precursors rich in dopamine. As transition metal carbides, WC and Mo₂C themselves have electronic properties similar to Pt and can catalyze the hydrogen evolution reaction (HER) of water electrolysis. When WC and Mo₂C combined to form heterojunctions and then Ru nanocrystals were loaded on them, strong electronic metal-support interaction was induced. During the formation of these composite Ru-WC/Mo₂C nanoparticles, the excess dopamine in the precursors polymerized to form a large amount of amorphous carbon, which not only served as a matrix for embedding Ru-WC/Mo₂C nanoparticles to prevent their agglomeration, but also acted as excellent conductive medium to promote the charge transport. When used as HER catalyst, compared with the pristine WC, Mo₂C and the WC/Mo₂C support, this unique structure exhibited significantly improved and long-term stable catalytic performance. In addition, Ru-WC/Mo₂C also revealed a significant feature that it could maintain this high catalytic performance over a wide pH range. For example, in electrolytes of 1 M KOH and 0.5 M H₂SO₄, the overpotentials, corresponding to current densities of 10 mA cm⁻¹, were 39.2 and 22.9 mV, respectively, and the Tafel slopes were 53.2 and 76 mV dec⁻¹, respectively. Such HER catalytic performance is very close to that of Pt. Considering the significant cost reduction of Ru-WC/Mo₂C compared to Pt, it is very promising that Ru-WC/Mo₂C would be used in the actual industrial hydrogen production by water electrolysis in the future.