Chinese Journal of Catalysis

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Electrosynthesis of nylon-6 precursor via heteroatom-doping- regulated oxygen vacancies engineering over ZnO

Suwei Lua,1, Hongping Yana,1, Hongwei Zhanga,b,1, Yuying Chenga, Xinxin Jianga, Xuyun Penga, Junwei Huanga, Yuanjin Lia,*, Xin Wangc, Shijing Lianga,b,*, Lilong Jianga,b   

  1. aState Key Laboratory of Fluorine & Nitrogen Chemicals, National Engineering Research Center of Chemical Fertilizer Catalyst, College of Chemical Engineering, Fuzhou University, Fuzhou 350002, Fujian, China;
    bQingyuan Innovation Laboratory, Quanzhou 362801, Fujian, China;
    cDepartment of Chemistry, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR, China
  • Received:2025-11-11 Accepted:2026-01-28
  • About author:1Contributed equally to this work.
  • Supported by:
    National Natural Science Foundation of China (22221005, 22378060, 22405049, 22308056) and the Natural Science Foundation of Fujian Province (2024J02009).

Abstract: Electrocatalysis is a green alternative to directly synthesize cyclohexanone oxime (CHOX, Nylon-6 precursor) via electrocatalytic reduction of nitrogen oxides to NH2OH and spontaneous C-N coupling with cyclohexanone, but suffering from a low-yield or poor Faradaic efficiency (FE) because of the scaling relationship. Herein, a strategy of heteroatom-doping-regulated oxygen vacancies (Vo) engineering was proposed to design a robust Cu-ZnO1‒x catalyst for efficient electrosynthesis of cyclohexanone oxime (ESCO). The complete characterizations and theoretical studies revealed that the doped-Cu can reduce Vo sites formation energy and regulate their local electronic state. The synergistic effect between doped Cu and Vo led to the break of the scaling relationship, presenting the enhancement of NO3- adsorption/dissociation, the weakness of H* adsorption, and the balance of the NH2OH adsorption for further C-N coupling reaction. Therefore, the hydrogen evolution reaction and NH2OH reduction to NH3 side reactions can be suppressed. The optimized Cu-ZnO1‒x delivered an outstanding activity with a 1238.8 μmol h‒1 mgcat.‒1 yield and 68.2% FE. Lastly, the reaction mechanism was established following *NO3 → *NO3H → *NO2 → *NO2H → *NO → *HNO → *NHOH → *NH2OH and spontaneous C-N coupling with cyclohexanone to form CHOX. The outstanding ESCO performance on Cu-ZnO1‒x catalyst demonstrates the effectiveness of this heteroatom-doping-regulated Vo engineering strategy.

Key words: Cyclohexanone oxime, Oxygen vacancy, Cu-doping, C-N coupling reaction, Electrocatalytic