Phase-selective synthesis of self-supported RuP films for efficient hydrogen evolution electrocatalysis in alkaline media.

Large-scale hydrogen production through alkaline water electrolysis requires highly active and less expensive materials to replace platinum as a catalyst for the hydrogen evolution reaction (HER). Ruthenium, as the cheapest platinum-group element, has recently been demonstrated to exhibit excellent activity toward the HER. However, achieving better HER activity of ruthenium-based materials by selecting a more active phase is still unexplored. Herein, we report the fabrication of self-supported RuP and RuP2 catalyst films on carbon cloth (RuP/CC and RuP2/CC) via a facile, potentially scalable, and phase-controllable synthetic method. RuP/CC displays superior catalytic activity with a low overpotential of 13 mV at 10 mA cm-1, outperforming RuP2/CC (33 mV at 10 mA cm-1) and most non-Pt HER catalysts. Moreover, good electrochemical stability and faradaic efficiency of nearly 100% are also demonstrated for RuP/CC. Density functional theory calculations reveal that RuP with a higher charge density at the Ru site is more favorable for the chemisorption of hydrogen, thereby exhibiting better HER activity than RuP2.