Modulating the Active Hydrogen Adsorption on FeDN Interface for Boosted Electrocatalytic Nitrate Reduction with Ultra-Long Stability

The electrocatalytic reduction of nitrate (NO3-) to nitrogen (N2) is an environmentally friendly approach for efficient N-cycle management (toward a nitrogen-neutral cycle). However, poor catalyst durability and the competitive hydrogen evolution reaction significantly impede its practical application. Interface-chemistry engineering, utilizing the close relationship between the catalyst surface/interface microenvironment and electron/proton transfer process, has facilitated the development of catalysts with high intrinsic activity and physicochemical durability. This study reports the synthesis of a nitrogen-doped carbon-coated rice-like iron nitride (RL-Fe2N@NC) electrocatalyst with excellent electrocatalytic nitrate-reduction reaction activity (high N2 selectivity (approximate to 96%) and NO3- conversion (approximate to 86%)). According to detailed mechanistic investigations by in situ tests and theoretical calculations, the strong hydrogenation ability of iron nitride and enhanced nitrate enrichment of the system synergistically contribute to the rapid hydrogenation of nitrogen-containing species, increasing the intrinsic activity of the catalyst and reducing the occurrence of the competing hydrogen-evolution side reaction. Moreover, RL-Fe2N@NC shows excellent stability, retaining good NO3--to-N2 electrocatalysis activity for more than 40 cycles (one cycle per day). This paper could guide the interfacial design of Fe-based composite nanostructures for electrocatalytic nitrate reduction, facilitating a shift toward nitrogen neutrality. A Fe-N interface is designed to ameliorate the utilization of active hydrogen for electrocatalytic nitrate reduction reaction to suppress the occurrence of hydrogen evolution reaction. In addition, RL-Fe2N@NC harvests superb stability due to the dual reinforcement of the internal Fe2N and the external carbon layer. This catalyst exhibits trade-offs between the scale-up application and the nitrogen-neutral cycle.image