Non-covalent ligand-oxide interaction promotes oxygen evolution
Qianbao Wu, Junwu Liang, Mengjun Xiao, Chang Long, Lei Li, Zhenhua Zeng, Andraž Mavrič, Xia Zheng, Jing Zhu, Hai‐Wei Liang, Hongfei Liu, Matjaž Valant, Wei Wang, Zhengxing Lv, Jiong Li, Chunhua Cui
Abstract
Abstract Strategies to generate high-valence metal species capable of oxidizing water often employ composition and coordination tuning of oxide-based catalysts, where strong covalent interactions with metal sites are crucial. However, it remains unexplored whether a relatively weak “non-bonding” interaction between ligands and oxides can mediate the electronic states of metal sites in oxides. Here we present an unusual non-covalent phenanthroline-CoO 2 interaction that substantially elevates the population of Co 4+ sites for improved water oxidation. We find that phenanthroline only coordinates with Co 2+ forming soluble Co(phenanthroline) 2 (OH) 2 complex in alkaline electrolytes, which can be deposited as amorphous CoO x H y film containing non-bonding phenanthroline upon oxidation of Co 2+ to Co 3+/4+ . This in situ deposited catalyst demonstrates a low overpotential of 216 mV at 10 mA cm −2 and sustainable activity over 1600 h with Faradaic efficiency above 97%. Density functional theory calculations reveal that the presence of phenanthroline can stabilize CoO 2 through the non-covalent interaction and generate polaron-like electronic states at the Co-Co center.