Wang Zhi, Han Yanjun, Wang Depeng, Zhao Daming, Zhong Haixia, Zhang Xinbo
China-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.
School of Applied Chemistry and Engineering, University of Science and Technology of China, 96 Jinzhai Street, Hefei, 230026, China.
Chemistry. 2025 Jul 25;31(42):e202501809. doi: 10.1002/chem.202501809. Epub 2025 Jul 11.
Metal-organic frameworks (MOFs) have been widely studied for various complex electrocatalytic reactions, such as nitrate reduction reaction (NORR) 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 Co(hexahydroxytriphenylene) (Co-HHTP) with Co-O units on carbon paper (CP) toward enhancing NORR. Both ZIF-67/CP and Co-HHTP/CP achieve NH 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 NH yield rates of 87.41 and 79.11 mg h cm, 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) compared to Co-HHTP. The newly generated Co(OH) 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.
金属有机框架材料（MOFs）已被广泛研究用于各种复杂的电催化反应，如硝酸盐还原反应（NORR）制氨。目前，由于MOFs在催化过程中不可避免的结构转变，其真正的活性位点存在争议，这限制了有效电催化剂的合理设计。在此，我们阐明了在碳纸（CP）上具有Co-N单元的沸石咪唑框架-67（ZIF-67）和具有Co-O单元的Co（六羟基三亚苯基）（Co-HHTP）在增强NORR方面的结构演变。相对于可逆氢电极（RHE），ZIF-67/CP和Co-HHTP/CP在-0.2至-1.0 V的宽电位范围内均实现了超过95%的NH法拉第效率。在相对于RHE为-1.0 V时，它们的NH产率分别为87.41和79.11 mg h cm，优于大多数已报道的基于MOF 的电催化剂。结合原位拉曼和非原位X射线衍射分析，我们验证了与Co-HHTP相比，ZIF-67向Co(OH)的转变更快。新生成的Co(OH)被认为是催化物种，原位傅里叶变换红外光谱和差分电化学质谱表明其具有更有利的氢化作用。这项工作为设计针对不同电化学反应的合理活性单元提供了对MOFs活性相的深刻理解。
