Anchoring carbon shells encapsulated RuMn nanoparticles on N-doped carbon nanofibers for efficient hydrogen evolution reaction

Abstract

Understanding the core-shell structure of carbon-encapsulated alloys aids in enhancing catalyst stability. DFT simulations reveal that the intrinsic electric field of the alloy modulates carbon atom behavior, effectively lowering the Gibbs free energy required for water dissociation and hydrogen adsorption on the carbon surface. Carbon-encapsulated RuMn alloy nanoparticles supported on carbon nanofibers (RuMn/CNFs) was fabricated as self-supporting electrode materials to validate this conclusion via a synergistic electrospinning‑carbonization protocol. The rational design of Ru/Mn stoichiometric modulation synergized with carbon nanofiber's superior electrical conductivity and RuMn/CNFs' hydrophilic-hydrophobic dual functionality endows the catalyst with exceptional alkaline hydrogen evolution performance. Specifically, the optimized RuMn/CNFs achieves a remarkably low overpotential of 80 mV at 100 mA cm⁻² coupled with an Tafel slope of 46.3 mV dec⁻¹. Analysis of surface morphology, internal structure, and changes in metal ion concentration in the electrolyte over various hydrogen production times revealed that Mn atoms, with lower electronegativity, leach from the graphite carbon-encapsulated alloy core-shell structure, creating defects on the surface of the RuMn alloy core. Atomic-scale interfacial interactions between RuMn lattice defects and the carbon shell orchestrate two synergistic effects: (1) enhance the adsorption of water onto the carbon shell, and (2) a 47 % reduction in water dissociation energy barriers (DFT-calculated). This dual modulation drives ultrafast Volmer step kinetics, endowing RuMn/CNFs with a good activity enhancement over pristine counterparts at industrial current densities (2.3 V at 500 mA cm⁻²). This work establishes a mechanistic framework for understanding dynamic interface reconstruction in carbon-encapsulated electrocatalysts, offering critical insights into operando structural evolution patterns and active site generation mechanisms during sustained HER operation.