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Amorphization mechanism of SrIrO3 electrocatalyst: How oxygen redox initiates ionic diffusion and structural reorganization

Authors : Gang Wan, John W. Freeland, Jan Kloppenburg, Guido Petretto, Jocienne N. Nelson, Ding-Yuan Kuo, Cheng-Jun Sun, Jianguo Wen, J. Trey Diulus, Gregory S. Herman, Yongqi Dong, Ronghui Kou, Jingying Sun, Shuo Chen, Kyle M. Shen, Darrell G. Schlom, Gian-Marco Rignanese, Geoffroy Hautier, Dillon D. Fong, Zhenxing Feng, Hua Zhou and Jin Suntivich.

The production of materials and fuels from widely available molecules is one of the most important challenges facing 21st-century society. Electrocatalysts function by providing environments conducive to the fuel and material electrosynthesis. However, developing high-performance electrocatalysts is far from straightforward. One of the major hurdles is the lack of information regarding the evolving structure of the electrocatalysts during the electrochemical operations. This knowledge gap is particularly problematic for the oxygen evolution reaction (OER), where the reaction environment is highly oxidizing and can rearrange the structure of the electrocatalyst. Given that the OER, the key electro-oxidation reaction, is one of the major causes of inefficiency in the fuel and material electrosynthesis, understanding the structural and chemical evolution of the electrocatalyst during the OER is essential to the development of active future electrocatalyst materials and, more broadly, to the prospect of materials and energy sustainability.

In this work, we provide atomic-level insight into the crystalline-toamorphous transformation and describe a mechanism that holistically connects the lattice oxygen activation, metal dissolution, and amorphization in SrIrO3. We focus on SrIrO3 , the state-of-the-art OER electrocatalyst in acid, to understand the origin of its high activity and track its interfacial evolution during the OER, providing the knowledge essential to the future electrocatalyst development. The theoretical modelling performed at UCLouvain complements a suite of synchrotron-based surface-sensitive x-ray techniques and electron microscopy to understand the surface transformation process. Our results show that the OER leads to the formation of an active ~2.4-nm-thick amorphous Sry IrO x film atop crystalline, highly defective “SrIrO3.”

https://advances.sciencemag.org/content/7/2/eabc7323

Science Advances  08 Jan 2021:
Vol. 7, no. 2, eabc7323
DOI: 10.1126/sciadv.abc7323

Published on January 11, 2021