Highly efficient sub-nanometer RuxCuyP2 nanoclusters designed for hydrogen evolution under alkaline media

The sub-nanometer Ru/Cu binary alloy phosphide nanoclusters over carbon nanofibers as low- ruthenium electrocatalysts to mediate HER in alkaline environment with high activity and long stability. [Display omitted] •The RuCuP2/CNF sub-nanometer nanoclusters (1.72 nm) are achieved through successive phosphorization step.•The RuCuP2/CNF sub-nanometer nanoclusters have a short electron diffusion distance, high surface-to-volume ratio.•The RuCuP2/CNF exhibits remarkable HER activity with low overpotential of j10 = 10 mV in alkaline solutions.•The superior HER activities of RuCuP2/CNF is systematically revealed by XPS test and ΔG0 calculations. Design of highly active and stable non-precious electrocatalysts towards hydrogen evolution reaction (HER) is a hot research topic in low cost, clean and sustainable hydrogen energy field, yet remaining the important challenge caused by the sluggish reaction kinetics for water-alkali electrolyzers. Herein, a robust electrocatalyst is proposed by designing a novel sub-nanometer of copper and ruthenium bimetallic phosphide nanoclusters (RuxCuyP2) supported on a graphited carbon nanofibers (CNF). Uniform RuxCuyP2 (~1.90 nm) on the surface of CNF are obtained by introducing the dispersed Ru, thereby improving the intrinsic activity for HER. On optimizing the Ru ratio, the (x = y = 1) RuCuP2/CNF catalyst exhibits an excellent HER electroactivity with an overpotential of 10 mV in 1.0 M NaOH electrolyte to produce 10 mA cm−2 current density, which is lower than commercial 20% Pt/C in alkaline solution. Moreover, the kinetic study demonstrated that electrochemical activation energies for HER of RuCuP2/CNF is 20.7 kJ mol−1 highest among different ratio bimetallic phosphide. This simple, cost-effective, and environmentally friendly methodology can pave the way for exploitation of bimetallic phosphide nanoclusters for catalyst design.