Triggering electronic coupling between neighboring hetero-diatomic metal sites promotes hydrogen evolution reaction kinetics

The emerging single atom catalysts (SACs) with tailorable, uniform and well-defined metal sites provide an ideal platform for studying the atomic-level correlation between structural configuration and catalytic behavior on heterogeneous catalysis. Here we demonstrate the electronic synergy of neighboring Ir and Ni diatomic sites on carbon supports (IrNi-N-C) for promoting the hydrogen evolution. The catalyst exhibits superior catalytic activity with low overpotentials (28 and 45 mV at 10 mA cm⁻²) and high turnover frequencies (TOFs, 3.06 and 1.40 H₂ s⁻¹ at 50 mV) in acidic and alkaline electrolytes, respectively. Theoretical and experimental results suggest that the incorporation of adjacent Ni-N₄ moiety increases the occupancy of Ir 5d orbitals and shifts the d-band center down in the IrNi-N-C catalyst, thus facilitating the catalytic process by the optimal intermediate binding energy. This work highlights the significance of Ni 3d-Ir 5d electronic coupling between neighboring single metal sites for catalytic activity, and paves a way for the SACs design by manipulating d-d electronic interaction except for tuning of the coordination ligands and the electronic metal-support interactions.