Iron-Catalyzed Selective Denitrification over N-Doped Mesoporous Carbon

Electrocatalytic denitrification has been considered as one of the most promising technologies to selectively reduce excessive nitrogen oxyanions to benign dinitrogen in polluted water. The development of nonprecious metal catalysts with high performance for the denitrification is imperative but still a great challenge. Herein, we report an iron-based electrocatalyst for high-efficiency and selective denitrification. This nanocatalyst is prepared by template assembly of iron-based metal organic frameworks on surface-functionalized bimodal mesoporous carbon and subsequent pyrolysis under argon atmosphere. It contains well-dispersed FeN sites and Fe nanoparticles (most of them are wrapped by N-doped graphitic carbon), with high surface area (1080 m² g^-1) and uniform mesopore and micropore (5.0 and 1.7 nm) for the construction of electrodes. Experimental results confirm that the catalyst can achieve an excellent nitrate removal capacity of 3410 mg N/g Fe, along with a reduction efficiency up to 87% and N₂ selectivity of 81% in neutral electrolyte (100 mg/L NO₃^--N and 0.1 M Na₂SO₄) within 24 h. It is proposed that the active FeN sites cooperated with sufficient Fe nanoparticles to be conducive to adsorption of O in NO₃^- on the catalyst for the improved performance. The material also presents long-term durability and good adaptability in the range of pH 5-9 and simulated neutral wastewater, mainly contributed by the protection of the mesostructure and graphitic N-doped carbon. These findings open the door to rational design of nonprecious metal iron-based functional electrocatalysts for water purification and environmental remediation.