Ligand effect on switching the rate-determining step of water oxidation in atomically precise metal nanoclusters

This study investigates the impact of ligands on the oxygen evolution reaction (OER) kinetics of atomically precise Au25 nanoclusters. Using para-mercaptobenzoic acid (pMBA), 6-mercaptohexanoic acid (MHA), and homocysteine (HCys) as ligands, the researchers demonstrate that ligand engineering can switch the rate-determining step of the OER. Au25 nanoclusters capped with pMBA exhibit superior performance, exhibiting almost four times higher activity than those capped with the other two ligands. This enhanced activity is attributed to pMBA's stronger electron-withdrawing ability, leading to increased partial positive charges on the Au(I) active sites, facilitating OH− adsorption. X-ray photoelectron spectroscopy and theoretical calculations support this finding. Tafel slopes and in situ Raman spectroscopy reveal different rate-determining steps for the different ligand-capped nanoclusters, providing mechanistic insights into the ligand's influence on OER catalysis.

Zhihe Liu, Hua Tan, Bo Li, Zehua Hu, De-en Jiang, Qiaofeng Yao, Lei Wang, Jianping Xie