Operando Direct Observation of Stable Water-Oxidation Intermediates on Ca2-xIrO4 Nanocrystals for Efficient Acidic Oxygen Evolution

Na Li, Liang Cai, Guoping Gao, Yue Lin, Chao Wang, Hengjie Liu, Yuying Liu, Hengli Duan, Qianqian Ji, Wei Hu, Hao Tan, Zeming Qi, Lin Wang Wang, Wensheng Yan

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


We report Ca2-xIrO4 nanocrystals exhibit record stability of 300 h continuous operation and high iridium mass activity (248 A gIr-1 at 1.5 VRHE) that is about 62 times that of benchmark IrO2. Lattice-resolution images and surface-sensitive spectroscopies demonstrate the Ir-rich surface layer (evolved from one-dimensional connected edge-sharing [IrO6] octahedrons) with high relative content of Ir5+ sites, which is responsible for the high activity and long-term stability. Combining operando infrared spectroscopy with X-ray absorption spectroscopy, we report the first direct observation of key intermediates absorbing at 946 cm-1 (Ir6+O site) and absorbing at 870 cm-1 (Ir6+OO- site) on iridium-based oxides electrocatalysts, and further discover the Ir6+O and Ir6+OO- intermediates are stable even just from 1.3 VRHE. Density functional theory calculations indicate the catalytic activity of Ca2IrO4 is enhanced remarkably after surface Ca leaching, and suggest IrOO- and IrO intermediates can be stabilized on positive charged active sites of Ir-rich surface layer.

Original languageEnglish (US)
JournalNano Letters
StateAccepted/In press - 2022

Bibliographical note

Funding Information:
This work was financially supported by the National Key Research and Development Program of China (2021YFA1600800), National Natural Science Foundation of China (Grants 11975234, 11775225, U2032150, U1932211, 12075243, 12005227 and 12105286), the Users with Excellence Program of Hefei Science Center CAS (No. 2020HSC-UE002, 2020HSC–CIP013, 2021HSC-UE002, 2021HSC-UE003), the Major science and technology project of Anhui Province (202103a05020025), the Key Program of Research and Development of Hefei Science Center, CAS (2021HSC-KPRD002), the Fundamental Research Funds for the Central Universities (WK 2310000103), the Postdoctoral Science Foundation of China (Grants 2020M682041, 2020TQ0316), and partially carried out at the USTC Center for Micro and Nanoscale Research and Fabrication. G.G. was supported by the “Young Talent Support Plan” of Xi’an Jiaotong University (Grant 11304222010715). L.W.W. was supported by the Director, Office of Science, the Office of Basic Energy Science (BES), Materials Sciences and Engineering (MSE) Division of the U.S. Department of Energy (DOE) through the theory of material (KC2301) program under Contract No. DEAC02-05CH11231. The authors would like to thank Beijing Synchrotron Radiation Facility (BSRF), Shanghai Synchrotron Radiation Facility (SSRF) and Beamlines MCD-A and MCD-B (Soochow Beamline for Energy Materials) at NSRL for the synchrotron beamtime.

Publisher Copyright:
© XXXX The Authors. Published by American Chemical Society.


  • acidic oxygen evolution reaction
  • electrocatalysis
  • iridium-based oxides
  • iridium-rich surface layer
  • key intermediates

ASJC Scopus subject areas

  • Bioengineering
  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics
  • Mechanical Engineering


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