Synergistic Ru-mediated activation of CoP/Co heterostructures on carbon nanofibers toward efficient hydrogen evolution

Abstract

Although cobalt-based phosphides exhibit promising hydrogen evolution activity, they still suffer from suboptimal hydrogen adsorption energy, sluggish water dissociation kinetics, and insufficient durability. Herein, we address this challenge by rationally constructing a highly integrated, self-supported HER electrode composed of Ru-doped CoP/Co heterostructures grown in situ on Co, N-doped electrospun carbon nanofibers (Ru–CoP/Co–NCNFs). The Ru–CoP/Co–NCNFs electrode exhibits markedly enhanced HER kinetics in both alkaline and acidic media. In alkaline medium, Ru–CoP/Co–NCNFs achieve overpotentials of 21 mV and 126 mV at 10 and 100 mA cm⁻², respectively, with a Tafel slope of 59.5 mV dec⁻¹, surpassing commercial 20% Pt/C. In acidic medium, overpotentials of 60 and 141 mV at 10 and 100 mA cm⁻², respectively, with a Tafel slope of 50.6 mV dec⁻¹, are obtained. Furthermore, negligible performance decay after 10 000 CV cycles and 200 h continuous operation at 10 mA cm⁻² highlights its remarkable durability. In situ FTIR spectroscopy directly reveals that Ru doping and the CoP/Co heterointerface promote the Volmer step of the HER. Density functional theory (DFT) calculations reveal that the synergistic effects of heterostructure engineering and Ru-induced electronic modulation reduce the reaction energy barrier of the CoP/Co heterostructure, modulate the electronic structure around the Co active center, and thereby enhance catalytic activity. The electrospun Co–N–C framework enables strong interfacial coupling with Ru–CoP/Co heterostructures and efficient charge transport across the electrode. This work offers valuable insights into optimizing transition metal phosphide-based HER electrocatalysts and provides a feasible strategy for the rational design of highly integrated, self-supported electrodes.