N-stabilized metal single atoms enabled rich defects for noble-metal alloy toward superior water reduction

The traditional methods of introducing defects into alloy catalysts, such as dealloying, quenching, and doping, usually require complicated processes, rendering less controllability to the products and performances. Herein, a simple fabrication method for vacancy-rich IrCo alloy nanoparticles supported on N-doped carbon sheets (denoted as D-IrCo/NC) is applied by post-annealing the single atom (Ir and Co) dispersed precursors. The mobile single atoms and the coalescences of metallic clusters are directly observed via in situ transmission electron microscopy. Compared to the alloy catalysts obtained by direct calcination or other traditional methods, the D-IrCo_4.9/NC catalyst is enriched with vacancy defects and only demands an overpotential of 14 mV at j = 10 mA/cm² for HER. Density functional theory (DFT) calculations reveal that the under-coordinated Ir sites possess the lowest hydrogen adsorption energy. This novel preparation method is universal, and this work also provides a facile strategy to fabricate highly defective alloy catalysts evolved from single atom precursors. (Figure presented.).