Chinese Journal of Catalysis

Chinese Journal of Catalysis

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Deciphering the synergy between electron localization and alloying for photoelectrochemical nitrogen reduction to ammonia

Zheng Jianyuna,†,*, Lyu Yanhonga,b,†, Huang Aibinc,d,†, Johannessen Bernte, Cao Xunc,d,#, Jiang San Pingf,$, Wang Shuangyina,‡   

  1. aState Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, Hunan, China;
    bDepartment of Educational Science, Hunan First Normal University, Changsha 410205, Hunan, China;
    cState Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China;
    dCenter of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China;
    eAustralian Synchrotron, Clayton, Victoria 3168, Australia;
    fWA School of Mines: Minerals, Energy and Chemical Engineering, Curtin University, Perth, WA 6102, Australia
  • Received:2022-07-13 Accepted:2022-09-01
  • Contact: * E-mail: jyzheng@hnu.edu.cn;# E-mail: cxun@mail.sic.ac.cn;$ E-mail: s.jiang@curtin.edu.au;‡ Tel: +86-731-88821411; E-mail: shuangyinwang@hnu.edu.cn
  • About author:† The first three authors contributed equally to this work.
  • Supported by:
    National Natural Science Foundation of China (22075075), the Key R&D Program of China (2020YFA0710000, 2021YFA1500900), the Outstanding Youth Scientist Foundation of Hunan Province (2022JJ10023), the Hunan Province of Huxiang Talent project (2021RC3051), the Provincial Natural Science Foundation of Hunan (2021JJ40140), the Research Foundation of Education Bureau of Hunan Province (21B0812).

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Abstract: Photoelectrochemistry that directly takes advantage of solar energy by photoelectrodes is a promising green route for the nitrogen fixation, but is currently far from practical application. It is necessary to understand the structure-reactivity interplay of the photocathodes for rendering rational improvement of the existing challenges. Here, we make efforts to reveal AuCoPd-CoOx/SiO2/Si photocathodes capable of selective photoelectrochemical conversion of nitrogen to ammonia at varied pressures, achieving an ammonia yield rate of 22.2 ± 0.4 μg·h-1·cm-2 and a faradic efficiency of 22.9% at -0.1 V vs. reversible hydrogen electrode under 3-MPa nitrogen. In particular, we focus on the remarkable, but often subtle, roles of the synergy between electron localization and alloying in determining the reactivity of the photocathodes. Specifically, operando XPS and XAS illustrate that the oxidation states of Au and Pd enable the photoinduced electron capture as the reduction sites to produce the *N2 and *H active species, respectively, facilitating the couple of N-H for ammonia synthesis. Although this study is not sufficient to break through bottleneck, there is much insight on the design of efficient and robust photocathodes for photoelectrochemical nitrogen fixation.

Key words: Photoelectrochemical nitrogen fixation, Electron localization, Alloying, Pressurized reaction, Synergy mechanism