Nitrogen-doped iron for selective catalytic reduction of nitrate to dinitrogen

Nitrate is the leading cause of eutrophication worldwide and is one of the most challenging pollutants for restoration of polluted surface waters such as lakes, rivers and reservoirs. We report herein a new architecture of iron nanoparticles for high-efficiency denitrification by selective reduction of nitrate (NO₃^-) to dinitrogen (N₂). The iron nanoparticles are doped with nitrogen (FeN) and encapsulated within a thin layer of nitride-carbon (NC). The nanoparticles have high pyrrolic N content (17.4 at.%) and large specific surface area (2040 m²/g). Laboratory experiments demonstrated high N₂ selectivity (91%) and nitrate removal capacity (6004 mg N/g Fe) for treatment of nitrate-containing water. This iron-based nanomaterial overcomes shortcomings of conventional catalysts by eliminating the use of precious and toxic heavy metals (e.g., Pd, Pt, Cu, Ni) and minimizing the generation of undesirable byproducts (e.g., ammonia) from the reactions with nanoscale zero-valent iron (nZVI). The multiple electron transfers process from NO₃^- to N₂ can be fine-tuned by adjusting the NC shell thickness. Superior electrocatalytic performance, low cost and minimal environmental impact of the iron-derived nanocatalyst offer promising prospects for water purification, waste treatment and environmental remediation.