Souza Marciélli K R, Cardoso Eduardo S F, Pinto Leandro M C, Crivelli Isabela S C, Rodrigues Clauber D, Souto Robson S, Rezende-Filho Ary T, Lanza Marcos R V, Maia Gilberto
Institute of Chemistry, Federal University of Mato Grosso do Sul, Avenida Senador Filinto Muller 1555, Campo Grande, Mato Grosso do Sul 79074-460, Brazil.
São Carlos Institute of Chemistry, University of São Paulo, Avenida Trabalhador São-Carlense 400, São CarlosSão Paulo 13566-590, Brazil.
ACS Appl Mater Interfaces. 2025 Jan 8;17(1):1295-1310. doi: 10.1021/acsami.4c18269. Epub 2024 Dec 27.
There has been huge interest among chemical scientists in the electrochemical reduction of nitrate (NO) to ammonia (NH) due to the useful application of NH in nitrogen fertilizers and fuel. To conduct such a complex reduction reaction, which involves eight electrons and eight protons, one needs to develop high-performance (and stable) electrocatalysts that favor the formation of reaction intermediates that are selective toward ammonia production. In the present study, we developed and applied CoO/graphene nanoribbon (GNR) electrocatalysts with excellent properties for the effective reduction of NO to NH, where NH yield rate of 42.11 mg h mg, FE of 98.7%, NO conversion efficiency of 14.71%, and NH selectivity of 100% were obtained, with the application of only 37.5 μg cm of the catalysts (for the best catalyst ─CoO(Cowt %55)GNR, only 20.6 μg cm of Co was applied), confirmed by loadings ranging from 19-150 μg cm. The highly satisfactory results obtained from the application of the proposed catalysts were favored by high average values of electrochemically active surface area (ECSA) and low values, along with the presence of several planes in CoO entangled with GNR and the occurrence of a kind of "(Co(Co(CN))(HO)) complex" structure on the catalyst surface, in addition to the effective migration of NO from the cell cathodic branch to the anodic branch, which was confirmed by the experiment conducted using a H-cell separated by a Nafion 117 membrane. The in situ FTIR and Raman spectroscopy results helped identify the adsorbed intermediates, namely, NO, NO, NO, and NHOH, and the final product NH, which are compatible with the proposed NO electroreduction mechanism. The Density Functional Theory (DFT) calculations helped confirm that the CoO(Cowt %55)GNR catalyst exhibited a better performance in terms of nitrate electroreduction in comparison with CoO(Cowt %75), considering the intermediates identified by the in situ FTIR and Raman spectroscopy results and the rate-determining step (RDS) observed for the transition of *NO to *NHO (0.43 eV).
由于氨在氮肥和燃料方面的有用应用，化学科学家们对将硝酸盐（NO）电化学还原为氨（NH₃）产生了浓厚兴趣。要进行这种涉及八个电子和八个质子的复杂还原反应，需要开发高性能（且稳定）的电催化剂，这种催化剂有利于形成对氨生产具有选择性的反应中间体。在本研究中，我们开发并应用了具有优异性能的CoO/石墨烯纳米带（GNR）电催化剂，用于将NO有效还原为NH₃，在仅施加37.5 μg cm⁻²的催化剂（对于最佳催化剂─CoO（Cowt %55）GNR，仅施加20.6 μg cm⁻²的Co）的情况下，获得了42.11 mg h⁻¹ mg⁻¹的NH₃产率、98.7%的法拉第效率（FE）、14.71%的NO转化效率和100%的NH₃选择性，通过19 - 150 μg cm⁻²的负载量得到证实。所提出的催化剂应用所获得的高度令人满意的结果得益于电化学活性表面积（ECSA）的高平均值和低的值，以及CoO中与GNR缠结的几个平面的存在和催化剂表面上一种“(Co(Co(CN))(H₂O))络合物”结构的出现，此外，通过使用由Nafion 117膜隔开的H型电池进行的实验证实了NO从电池阴极分支向阳极分支的有效迁移。原位FTIR和拉曼光谱结果有助于识别吸附的中间体，即NO、NO₂、NO₃和NHOH，以及最终产物NH₃，这与所提出 的NO电还原机理相符。密度泛函理论（DFT）计算有助于证实，考虑到原位FTIR和拉曼光谱结果所识别的中间体以及观察到的NO向NHOH转变的速率决定步骤（RDS）（0.43 eV），CoO（Cowt %55）GNR催化剂在硝酸盐电还原方面表现出比CoO（Cowt %75）更好的性能。
