Surface enrichment of iridium on IrCo alloys for boosting hydrogen production

We report a facile synthesis of an Ir surface-enriched IrCo alloy catalyst and its excellent activity which outperforms commercial Pt/C for the hydrogen evolution reaction (HER) in acidic media showing fast kinetics. The as-synthesized catalyst exhibits low overpotentials of merely 9 mV and 29.3 mV to afford current densities of 10 and 100 mA cm⁻², respectively, a turnover frequency of 1.25 s⁻¹, a low Tafel slope of 23.7 mV dec⁻¹, and stability for 100 h at a high current density of 100 mA cm⁻²in 0.5 M H₂SO₄electrolyte. Experiments and density functional theory (DFT) calculations indicate that the enrichment of Ir atoms on the outer surface of IrCo alloys is responsible for the effectively optimized free energy of hydrogen adsorption, which boosts the kinetics and HER performance. Our finding provides an insight into the metal surface enrichment on alloy nanoparticles (NPs).