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

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

83 Scopus citations

Abstract

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-IrOx) demonstrates outstanding water oxidation activity with an OER current density of 10 mA/cm2 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-IrOx and rutile IrO2 own similar [IrO6] octahedron units but have different [IrO6] 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-IrOx, but not on rutile IrO2 under OER operando conditions. The much more "flexible" disordered [IrO6] octahedrons with higher oxidation states in amorphous Li-IrOx as compared to the periodically interconnected "rigid" [IrO6] octahedrons in crystalline IrO2 are able to act as more electrophilic centers and thus effectively promote the fast turnover of water oxidation.

Original languageEnglish
Pages (from-to)3014-3023
Number of pages10
JournalJournal of the American Chemical Society
Volume141
Issue number7
DOIs
StatePublished - 20 Feb 2019

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