Zeolitic Imidazolate Framework Derived Fe Catalyst Electrocatalytic-Driven Atomic Hydrogen for Efficient Reduction of Nitrate to N2

Excessive discharge of nitrogen-containing chemical products into the natural water environment leads to the serious environmental problem of nitrate-nitrogen pollution, threatening the ecological balance and human health. In this study, we propose an efficient denitrification electrochemical method utilizing iron-doped zeolite imidazolium framework derived defective nitrogen-doped carbon (d-FeNC) catalysts. The d-FeNC catalyst exhibited 97% nitrate removal efficiency and 94% total nitrogen (TN) removal, and the reaction rate constant was increased from 0.73h-1 of the Fe-undoped electrocatalyst (d-NC) to 1.11h-1. The successful synthesis of d-FeNC with carbon defect sites and encapsulated Fe was confirmed by in-depth characterization. In situ electron paramagnetic resonance (EPR) analysis in conjunction with cyclic voltammetry (CV) tests confirmed the carbon substrates with defect enhanced the trapping of atomic hydrogen (H*) on the catalyst surface. Density functional theory (DFT) calculations clarified the doping of Fe facilitated the adsorption of nitrate, resulting in contact of H* with nitrate on the catalyst surface. In the synergy of the defective state organic framework and metal Fe, H* and nitrate realized a collision process. The electrochemical denitrification system achieved an excellent nitrate removal capacity of 7587 mgN·g-1cat in high-concentration nitrate solution and showed excellent stability under various conditions. Overall, this study underscores the potential of defective iron-doped carbon catalysts for efficient electrocatalytic denitrification, providing a promising approach for sustainable wastewater treatment. Environmental Implication The accumulation of nitrate-N (NO3--N) in environmental waters has caused serious environmental pollution, threatening ecological balance and human health. In particular, the by-product nitrite-N (NO2--N) from accumulated nitrate has been recognized as a precursor of potential carcinogens, leading to massive mortality of aquatic organisms and even causing damage to the human liver. In this study, metal doping and defect engineering techniques were employed to achieve effective contact between reducing active species and NO3--N, enabling electrocatalytic efficient treatment of nitrate pollutants in real water bodies.