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Updated: Sep 17, 2025
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Published on: December 6, 2021
Unraveling Structural Evolution of Cobalt-Based Metal-Organic Frameworks for Boosting Nitrate Electroreduction to
Zhi Wang1,2,3, Yanjun Han1,2,3, Depeng Wang1,2,3
1China-Belarus Belt and Road Joint Laboratory on Advanced Materials and Manufacturing, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun, 130022, China.
Abstract:
Metal-organic frameworks (MOFs) have been widely studied for various complex electrocatalytic reactions, such as nitrate reduction reaction (NO3RR) to ammonia. Currently, their real active sites are controversial due to the inevitable structure transformations of MOFs during the catalytic process, limiting the rational design of effective electrocatalysts. Here, we clarified the structural evolution of zeolitic imidazole framework-67 (ZIF-67) with Co-N units and Co3(hexahydroxytriphenylene)2 (Co-HHTP) with Co-O units on carbon paper (CP) toward enhancing NO3RR. Both ZIF-67/CP and Co-HHTP/CP achieve NH3 Faradaic efficiencies more than 95% within the wide potential range of -0.2 to -1.0 V versus reversible hydrogen electrode (RHE). At -1.0 V versus RHE, they deliver NH3 yield rates of 87.41 and 79.11 mg h-1 cm-2, respectively, which outperform the most reported MOF-based electrocatalysts. Combining with in-situ Raman and ex-situ X-ray diffraction analysis, we verified the faster transformation of ZIF-67 into Co(OH)2 compared to Co-HHTP. The newly generated Co(OH)2 was recognized as the catalytic species and presented more favorable hydrogenation as elucidated by in-situ Fourier transform infrared and differential electrochemical mass spectroscopy. This work offers insightful understanding on the active phase of MOFs for designing reasonable active units toward different electrochemical reactions.
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