关键词: 碳纳米纤维, 银-钴双金属颗粒, Janus结构, 界面工程, 电催化硝酸根还原反应

Abstract: " The efficient reduction of nitrate (NO3⁻) to ammonia (NH3) via electrocatalysis is critical for both environmental remediation and sustainable nitrogen cycle management. However, traditional single-metal catalysts often exhibit poor catalytic performance due to weak adsorption of NO3⁻ and the complex, multi-step nature of the nitrate reduction reaction (NO3RR). In this study, we addressed these challenges by designing a bimetallic catalyst with a Janus structure, Ag-Co/CNFs, enhancing the catalytic performance for NO3RR. The catalyst was prepared using a combination of electrospinning and high-temperature calcination, which facilitated the formation of Ag-Co interfaces within carbon nanofibers (CNFs). The results show that by controlling the high-temperature calcination temperature, Ag-Co bimetallic particles with a Janus structure can be prepared, thereby forming an Ag-Co interface. Characterization of the Ag-Co/CNFs material was carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and X-ray diffraction (XRD). The SEM and TEM images reveal the uniform distribution of Ag and Co in the catalyst, while HRTEM demonstrates the successful formation of the Ag-Co interface. XRD analysis indicates that the crystal structure of Ag-Co/CNFs is highly stable under different annealing conditions. The formation of the Ag-Co interface stabilizes the reaction current density, enhances the number of active sites for multi-step reactions, and facilitates the transfer of reaction intermediates between active sites, thereby improving ammonia selectivity. Additionally, the formation of the Ag-Co interface results in a lower Rct for the catalyst, which promotes the transport of charge carriers, increasing the current density and ammonia production rate. Ag-Co/CNFs combines the advantages of Co/CNFs in high nitrite conversion and overcomes the limitation of Ag/CNFs in nitrite conversion at low potentials. At -1.2 V vs. Hg/HgO, it achieves an NH3 Faradaic efficiency (FE) of up to 90.23%, and at -1.9 V vs. Hg/HgO, it reaches an ammonia production rate of 707.82 μmol/(h·cm2). Furthermore, the catalyst was compared with other single-metal catalysts, Ag/CNFs and Co/CNFs, showing superior performance in both Faradaic efficiency and ammonia production rate. This study highlights the advantages of phase interface engineering in electrocatalysis, offering a promising approach for the design of high-performance, stable catalysts for nitrate reduction reactions. The findings from this study not only provide insight into the role of phase interfaces in improving catalytic performance but also pave the way for the development of multi-metal catalysts with enhanced efficiency for other complex electrocatalytic reactions."

Key words: carbon nanofibers, silver-cobalt bimetallic particles, Janus structure, interface engineering, NO3RR