First principles calculation study of single transition metal atom grafted Au25 as efficient electrocatalysts for OER and ORR

Abstract

The method of grafting metal atoms by ligands can construct 'grafted single-atom catalysts' with good catalytic activity without destroying the cluster structure. In this study, the catalytic performance of Fe2+, Co2+ and Ni2+ grafted Au25(SR)18 cluster through l-cysteine ligand as bridging ligand (denoted as Au25-nCys-M, where n is the number of grafted Cys-ligand) in OER and ORR was investigated by density functional theory (DFT) simulations. A volcanic diagram between the overpotential of OER and ORR and the adsorption free energy of intermediates on Au25–nCys-M was determined, which showed that the adsorption strength of oxygenated intermediates can be adjusted by the grafting method and the number of bridging ligands, thus affecting the catalytic performance. Among three kinds of metal ions, the grafted Ni2+single atom catalysts showed excellent bi-functional OER and ORR activities. In particular, the Au25–1Cys-Ni2+ (n = 1) had the lowest overpotentials of 0.48 and 0.27 V for OER and ORR. Through in-depth analysis, we found that the spin magnetic moments of metal cations can be used as the descriptor of the catalytic performance of the grafted single atom catalyst. The excellent catalytic performance of Au25–nCys-Ni2+was originated from the smaller spin magnetic moment of Ni2+. These findings provided new idea for the preparation of nanocomposites with excellent OER and ORR catalytic performance.