Construction of Feδ+–Ruδ− synergistic interface enabling efficient and stable hydrogen evolution in versatile electrolytes

• • FeRu-ERBC achieves an overpotential of only 22.7 mV at 10 mA·cm−2 in 1.0 M KOH, outperforming commercial Pt/C and enabling energy-efficient hydrogen production in alkaline media. • • The catalyst demonstrates exceptional long-term stability exceeding 120 hours in alkaline seawater and chemical wastewater, addressing the critical durability bottleneck for practical electrolysis in complex electrolytes. • • The biomass-derived carbon support induces near-complete Fe substitution by Ru, forming an atomically intimate Fe–Ru interface with electron transfer from Fe to Ru, as confirmed by XPS and Bader charge analysis, which optimizes hydrogen adsorption free energy (ΔGH) and lowers the water dissociation barrier. • • FeRu-ERBC maintains high HER activity across versatile electrolytes (alkaline, seawater, wastewater), with overpotential and stability metrics indicating resistance to chloride ion poisoning and corrosion, making it suitable for direct use in non-freshwater sources.