Dual-sided single-atom bridges with interfaces for high-efficiency acidic water electrolysis: interfacial engineering beyond sacrificial corrosion resistance

Water electrolysis is a promising route to sustainable hydrogen, but catalysts often corrode and operate slowly in high-salinity environments. We develop a dual-sided single-atom bridge (DS-SAB) electrocatalyst by isolating Fe single atoms on a Janus N-doped carbon matrix (DS-FeSACs-C@NC). The Fe-N_x/C side optimizes oxygen evolution reaction (OER) by modulating OH⁻ adsorption, while the Fe[sbnd]C side accelerates hydrogen evolution reaction (HER) by facilitating H* intermediate desorption. The Janus interlayer with vertically aligned graphene edges and N groups act as an anion-repelling barrier without sacrificing ionic conductivity. As a result, DS-SAB delivers record-low overpotentials of 76 mV (HER) and 253 mV (OER) at 10 mA cm⁻² in 0.1 M H₂SO₄, and sustains 10 mA cm⁻² for over 200 h. These achievements are attributed to the bidirectional electron transfer between Fe-N_x/C and Fe[sbnd]C sites, which tunes adsorption barriers, while an interfacial electric field accelerates electron flow, lowers impedance, and boosts catalytic kinetics. This work offers a paradigm for designing corrosion-resistant catalysts in complex electrolytes through atomic-scale interface control.