Stabilizing Highly Active Ru Sites by Suppressing Lattice Oxygen Participation in Acidic Water Oxidation

Creators: Wen, Yunzhou¹; Chen, Peining^{1, 2}; Wang, Lu^{3, 4}; Li, Shangyu¹; Wang, Ziyun²; Abed, Jehad²; Mao, Xinnan³; Min, Yimeng²; Dinh, Cao Thang⁵; De Luna, Phil²; Huang, Rui¹; Zhang, Longsheng¹; Wang, Lie¹; Wang, Liping¹; Nielsen, Robert J.⁴; Li, Huihui²; Zhuang, Taotao²; Ke, Changchun⁶; Voznyy, Oleksandr²; Hu, Yongfeng⁷; Li, Youyong³; Goddard, William A., III⁴; Zhang, Bo¹; Peng, Huisheng¹; Sargent, Edward H.²

1. Fudan University
2. University of Toronto
3. Soochow University
4. California Institute of Technology
5. Queen's University
6. Shanghai Jiao Tong University
7. Canadian Light Source (Canada)

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Abstract

In hydrogen production, the anodic oxygen evolution reaction (OER) limits the energy conversion efficiency and also impacts stability in proton-exchange membrane water electrolyzers. Widely used Ir-based catalysts suffer from insufficient activity, while more active Ru-based catalysts tend to dissolve under OER conditions. This has been associated with the participation of lattice oxygen (lattice oxygen oxidation mechanism (LOM)), which may lead to the collapse of the crystal structure and accelerate the leaching of active Ru species, leading to low operating stability. Here we develop Sr–Ru–Ir ternary oxide electrocatalysts that achieve high OER activity and stability in acidic electrolyte. The catalysts achieve an overpotential of 190 mV at 10 mA cm⁻² and the overpotential remains below 225 mV following 1,500 h of operation. X-ray absorption spectroscopy and ¹⁸O isotope-labeled online mass spectroscopy studies reveal that the participation of lattice oxygen during OER was suppressed by interactions in the Ru–O–Ir local structure, offering a picture of how stability was improved. The electronic structure of active Ru sites was modulated by Sr and Ir, optimizing the binding energetics of OER oxo-intermediates.

Additional Information

© 2021 American Chemical Society. Received: January 12, 2021. This work was supported by MOST (2016YFA0203302), NSFC (21634003, 51573027, 21875042, 21805044, and 21771170), STCSM (16JC1400702, 18QA140080, and 19QA140080), SHMEC (2017-01-07-00-07-E00062), and Yanchang Petroleum Group. This work was also supported by the Program for Eastern Scholars at Shanghai Institutions. This work was supported by the Ontario Research Fund - Research Excellence Program, NSERC, and the CIFAR Bio-Inspired Solar Energy program. The ex situ XAFS was carried out at the BL14W1 beamline, Shanghai Synchrotron Radiation Facility (SSRF). The in situ Ru K-edge and Ir L₃-edge XAFS was measured at the 1W1B beamline, Beijing Synchrotron Radiation Facility (BSRF). The in situ Ru L₃-edge measurements were carried out at the soft X-ray microcharacterization beamline (SXRMB) in Canadian Light Source (CLS). The STEM imaging part of this research was completed at the Analytical and Testing Center, Northwestern Polytechnical University. The Caltech studies were supported by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award DE-SC0004993, by NSF (CBET-1805022), and by DOE AMO. Author Contributions: Y.W., P.C., L.W., and S.L. contributed equally to this work. The authors declare no competing financial interest.

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