Breaking Long-Range Order in Iridium Oxide by Alkali Ion for Efficient Water Oxidation

作者：Jiajian Gao, Cong‐Qiao Xu, Sung‐Fu Hung, Wei Liu, Weizheng Cai, Zhiping Zeng, Chunmiao Jia, Hao Ming Chen, Hai Xiao, Jun Li, Yanqiang Huang, Bin Liu · 发表于：Journal of the American Chemical Society · 年份：2019 · DOI：10.1021/jacs.8b11456 · 被引用次数：549 · 研究领域：Electrocatalysts for Energy Conversion、Advanced battery technologies research、Advanced Photocatalysis Techniques

Oxygen electrochemistry plays a critical role in clean energy technologies such as fuel cells and electrolyzers, but the oxygen evolution reaction (OER) severely restricts the efficiency of these devices due to its slow kinetics. Here, we show that via incorporation of lithium ion into iridium oxide, the thus obtained amorphous iridium oxide (Li–IrO x ) demonstrates outstanding water oxidation activity with an OER current density of 10 mA/cm 2 at 270 mV overpotential for 10 h of continuous operation in acidic electrolyte. DFT calculations show that lithium incorporation into iridium oxide is able to lower the activation barrier for OER. X-ray absorption characterizations indicate that both amorphous Li–IrO x and rutile IrO 2 own similar [IrO 6 ] octahedron units but have different [IrO 6 ] octahedron connection modes. Oxidation of iridium to higher oxidation states along with shrinkage in the Ir–O bond was observed by in situ X-ray absorption spectroscopy on amorphous Li–IrO x, but not on rutile IrO 2 under OER operando conditions. The much more “flexible” disordered [IrO 6 ] octahedrons with higher oxidation states in amorphous Li–IrO x as compared to the periodically interconnected “rigid” [IrO 6 ] octahedrons in crystalline IrO 2 are able to act as more electrophilic centers and thus effectively promote the fast turnover of water oxidation.