A Spectroscopically Observed Iron Nitrosyl Intermediate in the Reduction of Nitrate by a Surface-Conjugated Electrocatalyst
A Spectroscopically Observed Iron Nitrosyl Intermediate in the Reduction of Nitrate by a Surface-Conjugated Electrocatalyst
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DOI：
10.1021/jacs.2c03487
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发表时间：
2022-09-26
影响因子：
15
通讯作者：
Smith, Jeremy M.
中科院分区：
文献类型：
--
作者：
Ghosh, Moumita;Braley, Sarah E.;Smith, Jeremy M.
我们报告了一种铁基石墨共轭电催化剂（GCC-FeDIM），它将均相分子电催化剂的明确性质与异质电极的稳健性结合在一起。由 DFT 计算结果支持的一套光谱方法表明，电极表面在 FeN4Cl2 配位环境中通过高自旋 (S = 5/2) Fe(III) 离子进行功能化。氯离子在水溶液中水解，所得循环伏安图显示高斯形波，归因于表面 Fe(III)-OH 表面的 1H+/1e- 还原。在 NO3- 存在的情况下观察到催化波，起始电位相对于 SCE 为 -1.1 V。在 pH 6.0 时，GCC-FeDIM 快速将 NO3- 还原为铵和亚硝酸盐，法拉第效率分别为 88% 和 6%。包括原位 X 射线吸收光谱在内的机理研究表明，电催化 NO3 还原涉及亚硝酰铁中间体。 Fe-N键长（1.65埃）与{Fe(NO)}6配合物中观察到的键长相似，这得到了DFT计算结果的支持。
We report an iron-based graphite-conjugated electrocatalyst (GCC-FeDIM) that combines the well-defined nature of homogeneous molecular electrocatalysts with the robustness of a heterogeneous electrode. A suite of spectroscopic methods, supported by the results of DFT calculations, reveals that the electrode surface is functionalized by high spin (S = 5/2) Fe(III) ions in an FeN4Cl2 coordination environment. The chloride ions are hydrolyzed in aqueous solution, with the resulting cyclic voltammogram revealing a Gaussian-shaped wave assigned to 1H+/1e- reduction of surface Fe(III)-OH surface. A catalytic wave is observed in the presence of NO3-, with an onset potential of -1.1 V vs SCE. At pH 6.0, GCC-FeDIM rapidly reduces NO3- to ammonium and nitrite with 88 and 6% Faradaic efficiency, respectively. Mechanistic studies, including in situ X-ray absorption spectroscopy, suggest that electrocatalytic NO3- reduction involves an iron nitrosyl intermediate. The Fe-N bond length (1.65 angstrom) is similar to that observed in {Fe(NO)}6 complexes, which is supported by the results of DFT calculations.