Zhang Jia-Jia, Lou Yao-Yin, Wu Zhangxiong, Huang Xiaoyang Jerry, Sun Shi-Gang
Particle Engineering Laboratory, School of Chemical and Environmental Engineering, and Suzhou Key Laboratory of Novel Semiconductor-optoelectronics Materials and Devices, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu 215123, China.
CAS Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, P. R. China.
J Am Chem Soc. 2024 Sep 11;146(36):24966-24977. doi: 10.1021/jacs.4c06657. Epub 2024 Aug 28.
Nitrate (NO) in wastewater poses a serious threat to human health and the ecological environment. The electrocatalytic NO reduction to ammonia (NH) reaction (NORR) emerges as a promising carbon-free energy route for enabling NO removal and sustainable NH synthesis. However, it remains a challenge to achieve high Faraday efficiencies at a wide potential window due to the complex multiple-electron reduction process. Herein, spatially separated dual-metal tandem electrocatalysts made of a nitrogen-doped ordered mesoporous carbon support with ultrasmall and high-content Cu nanoparticles encapsulated inside and large and low-content Ru nanoparticles dispersed on the external surface (denoted as Ru/Cu@NOMC) are designed. In electrocatalytic NORR, the Cu sites can quickly convert NO to adsorbed NO (*NO), while the Ru sites can efficiently produce active hydrogen (*H) to enhance the kinetics of converting *NO to NH on the Cu sites. Due to the synergistic effect between the Cu and Ru sites, Ru/Cu@NOMC exhibits a maximum NH Faradaic efficiency (FE) of approximately 100% at -0.1 V vs reversible hydrogen electrode (RHE) and a high NH yield rate of 1267 mmol g h at -0.5 V vs RHE. Finite element method (FEM) simulation and electrochemical in situ Raman spectroscopy revealed that the mesoporous framework can enhance the intermediate concentration due to the in situ confinement effect. Thanks to the Cu-Ru synergistic effect and the mesopore confinement effect, a wide potential window of approximately 500 mV for FE over 90% and a superior stability for NH production over 156 h can be achieved on the Ru/Cu@NOMC catalyst.
废水中的硝酸盐（NO）对人类健康和生态环境构成严重威胁。电催化将NO还原为氨（NH₃）的反应（NORR）作为一种有前景的无碳能源途径，可实现NO的去除和可持续的NH₃合成。然而，由于复杂的多电子还原过程，在宽电位窗口下实现高法拉第效率仍然是一个挑战。在此，设计了一种空间分离的双金属串联电催化剂，它由氮掺杂的有序介孔碳载体组成，内部包裹着超小且高含量的铜纳米颗粒，外表面分散着大尺寸且低含量的钌纳米颗粒（表示为Ru/Cu@NOMC）。在电催化NORR中，Cu位点可快速将NO转化为吸附态的NO（*NO），而Ru位点能高效产生活性氢（H），以增强在Cu位点上NO转化为NH₃的动力学。由于Cu和Ru位点之间的协同效应，Ru/Cu@NOMC在相对于可逆氢电极（RHE）为-0.1 V时表现出约100%的最大NH₃法拉第效率（FE），在相对于RHE为-0.5 V时具有1267 mmol g⁻¹ h⁻¹的高NH₃产率。有限元方法（FEM）模拟和电化学原位拉曼光谱表明，介孔框架由于原位限域效应可提高中间体浓度。得益于Cu-Ru协同效应和介孔限域效应，在Ru/Cu@NOMC催化剂上可实现约500 mV的宽电位窗口，FE超过90%，并且在NH₃生产方面具有超过156 h的优异稳定性。
