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We report an iron-based graphite-conjugated electrocatalyst (GCC-FeDIM) that combines the well-defined nature of homogeneous molecular electrocatalysts with the robustness of a heterogeneous electrode. A suite of spectroscopic methods, supported by the results of DFT calculations, reveals that the electrode surface is functionalized by high spin (S = 5/2) Fe (III) ions in an FeN4Cl2 coordination environment. The chloride ions are hydrolyzed in aqueous solution, with the resulting cyclic voltammogram revealing a Gaussian-shaped wave assigned to 1H+/1e- reduction of surface Fe (III) –OH surface. A catalytic wave is observed in the presence of NO3–, with an onset potential of −1. 1 V vs SCE. At pH 6. 0, GCC-FeDIM rapidly reduces NO3– to ammonium and nitrite with 88 and 6% Faradaic efficiency, respectively. Mechanistic studies, including in situ X-ray absorption spectroscopy, suggest that electrocatalytic NO3– reduction involves an iron nitrosyl intermediate. The Fe–N bond length (1. 65 Å) is similar to that observed in Fe (NO) 6 complexes, which is supported by the results of DFT calculations.
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