Single Iridium Atom Doped Ni₂P Catalyst for Optimal Oxygen Evolution

Single-atom catalysts (SACs) with 100% active sites have excellent prospects for application in the oxygen evolution reaction (OER). However, further enhancement of the catalytic activity for OER is quite challenging, particularly for the development of stable SACs with overpotentials <180 mV. Here, we report an iridium single atom on Ni₂P catalyst (Ir_SA-Ni₂P) with a record low overpotential of 149 mV at a current density of 10 mA·cm^-2 in 1.0 M KOH. The Ir_SA-Ni₂P catalyst delivers a current density up to ∼28-fold higher than that of the widely used IrO₂ at 1.53 V vs RHE. Both the experimental results and computational simulations indicate that Ir single atoms preferentially occupy Ni sites on the top surface. The reconstructed Ir-O-P/Ni-O-P bonding environment plays a vital role for optimal adsorption and desorption of the OER intermediate species, which leads to marked enhancement of the OER activity. Additionally, the dynamic "top-down" evolution of the specific structure of the Ni@Ir particles is responsible for the robust single-atom structure and, thus, the stability property. This Ir_SA-Ni₂P catalyst offers novel prospects for simplifying decoration strategies and further enhancing OER performance.