Fe/N modified porous carbon nanofibers with encapsulated FeCo nanoparticles for efficient electrocatalytic nitrate reduction to ammonia.

The efficient electrocatalytic nitrate (NO) reduction to ammonia (NRA) offers a sustainable alternative for both environmental remediation and ammonia synthesis. Developing advanced electrocatalysts with rationally designed spatial arrangement of active sites and optimizing the synergetic effect among components are crucial for high efficiency and selectivity. Herein, we present Fe/N active sites decorated on porous carbon nanofibers (CNFs) with encapsulated FeCo nanoparticles (FeCo@CNFs-Fe/N) as electrocatalysts for NRA. The FeCo@CNFs-Fe/N catalyst demonstrates exceptional performance, achieving a high ammonia yield of 498.18 µmol/(h·g). Meanwhile, the enhanced reduction activity, especially the reduction in overpotential by 0.565 V, is 3-10 times higher than that of FeCo-encapsulated and Fe/N-modified CNFs-based catalysts. The enhanced catalytic activity is attributed to the efficient structure design and optimized spatial distribution of active sites, which enhance the electron transfer rate and decrease the reaction energy barrier. Mechanistic studies reveal that the synergetic effect between encapsulated nanoparticles and surface-modified Fe/N sites plays a crucial role in promoting efficient nitrate adsorption and selective ammonia production. These findings highlight the potential of strategically engineered CNF-based composites for nitrate reduction and other advanced electrocatalytic applications.