Amorphous phosphatized ruthenium-iron bimetallic nanoclusters with Pt-like activity for hydrogen evolution reaction

The ultrasmall sized, highly dispersed and amorphous phosphatized ruthenium-iron bimetallic nanoclusters (RuxFeyP-NCs) uniformly coated on carbon nanofibers (CNF) have been designed for boosting HER. [Display omitted] •RuxFeyP-NCs/CNF catalysts have the amorphous and ultrasmall structure with the average size of 1.77 nm.•Amorphous structures provide more electrocatalytically active sites being exposed.•The RuFeP-NCs/CNF exhibits boosting HER under acidic and alkaline conditions with low overpotentials.•The RuFeP-NCs/CNF exhibits comparatively low Tafel slopes and outstanding long-term stability.•The superior HER activities of RuFeP-NCs/CNF is systematically revealed by DFT calculations. Transition metallic phosphides (TMPs) have attracted considerable attention for use as efficient and durable electrocatalysts for the hydrogen evolution reaction (HER). However, it is still challenging for TMPs to achieve HER performance similar to that of the state-of-the-art platinum (Pt) catalysts. Herein, we report new amorphous phosphatized ruthenium-iron bimetallic nanoclusters (RuxFeyP-NCs) supported on graphitized carbon nanofibers (CNF), synthesized through a facile two-step method, which combine the merits of several catalyst design strategies. The amorphous structure allows more catalytically active sites to be exposed, and the synergy between Ru and Fe may boost the intrinsic catalytic activity. Moreover, the conductive CNF support facilitates electron transport and firmly immobilizes RuxFeyP-NCs enabling a long-term stability. The resulting RuxFeyP-NCs/CNF with optimal equimolar Ru and Fe (i.e. RuFeP-NCs/CNF) exhibits outstanding Pt-like HER performance, requiring low overpotentials of 65.8 and 16.0 mV to deliver a current density of 10 mA cm−2 in acidic and alkaline solutions, respectively, and showing a long-term stability of 100 h. The density functional theory (DFT) calculations demonstrate that RuFeP-NCs/CNF shows Gibbs free energy of hydrogen adsorption close to that of Pt and much smaller than that of FeP-NCs/CNF and RuxFey-NCs/CNF controls with non-equimolar Ru/Fe, which rationally explains the experimentally observed prominent HER performance of RuFeP-NCs/CNF.