(Invited) Electroreduction of Nitrogen to Ammonia at Iron Catalytic Sites Generated at Interfaces Utilizing Iron Phosphides and Heme-Type Complexes

Abstract

There has been growing interest in the development of durable, specific and reasonably efficient low-cost catalysts for nitrogen (N2) electroreduction reaction, or nitrogen fixation, particularly in aqueous solutions capable of producing ammonia under ambient, or near ambient, conditions. The successful electrocatalytic reduction of nitrogen (N2) and formation of NH3 in alkaline an medium has been reported here using the Fe3P phase of iron phosphide. Detection of in-situ formed product has been achieved by probing the electrooxidation of NH3 to nitrogen (N2) using the additional working electrode modified with Pt nanoparticles. On mechanistic grounds, the iron (Fe0) sites seem to be electrocatalytic active during the reduction of nitrogen. The iron sites can also be generated within the phtalocyanine ring binding metal ions through four inwardly projecting nitrogen centers. Furthermore, horseradish peroxidase metalloenzyme, in which a large alpha-helical protein binds heme as a redox cofactor, is capable of inducing electroduction of N2.