Bai Lichen, Franco Federico, Timoshenko Janis, Rettenmaier Clara, Scholten Fabian, Jeon Hyo Sang, Yoon Aram, Rüscher Martina, Herzog Antonia, Haase Felix T, Kühl Stefanie, Chee See Wee, Bergmann Arno, Beatriz Roldan Cuenya
Department of Interface Science, Fritz-Haber-Institute of Max-Planck-Society, Faradayweg 4-6, 14195 Berlin, Germany.
J Am Chem Soc. 2024 Apr 10;146(14):9665-9678. doi: 10.1021/jacs.3c13288. Epub 2024 Apr 1.
The electrochemical reduction of nitrate (NO) and nitrite (NO) enables sustainable, carbon-neutral, and decentralized routes to produce ammonia (NH). Copper-based materials are promising electrocatalysts for NO conversion to NH. However, the underlying reaction mechanisms and the role of different Cu species during the catalytic process are still poorly understood. Herein, by combining quasi in situ X-ray photoelectron spectroscopy (XPS) and operando X-ray absorption spectroscopy (XAS), we unveiled that Cu is mostly in metallic form during the highly selective reduction of NO/NO to NH. On the contrary, Cu(I) species are predominant in a potential region where the two-electron reduction of NO to NO is the major reaction. Electrokinetic analysis and in situ Raman spectroscopy was also used to propose possible steps and intermediates leading to NO and NH, respectively. This work establishes a correlation between the catalytic performance and the dynamic changes of the chemical state of Cu, and provides crucial mechanistic insights into the pathways for NO/NO electrocatalytic reduction.
硝酸盐（NO₃⁻）和亚硝酸盐（NO₂⁻）的电化学还原为生产氨（NH₃）提供了可持续、碳中和且分散化的途径。铜基材料是将NO₃⁻转化为NH₃的有前景的电催化剂。然而，催化过程中的潜在反应机制以及不同铜物种的作用仍知之甚少。在此，通过结合准原位X射线光电子能谱（XPS）和原位X射线吸收光谱（XAS），我们揭示了在将NO₃⁻/NO₂⁻高度选择性还原为NH₃的过程中，铜主要以金属形式存在。相反，在NO₂⁻双电子还原为NO的主要反应的电位区域中，Cu(I)物种占主导。还使用了动电分析和原位拉曼光谱分别提出了生成NO和NH₃的可能步骤和中间体。这项工作建立了催化性能与铜化学状态动态变化之间的关联，并为NO₃⁻/NO₂⁻电催化还原途径提供了关键的机理见解。
