Metallophthalocyanine catalysed electroreduction of nitrate and nitrite ions in alkaline media

The electrochemical reduction of nitrite and nitrate in alkaline solution has been studied on glassy carbon electrodes modified with phthalocyanine complexes of Mn, Fe, Co, Ni, Cu and Zn (MnPc, FePc, CoPc, NiPc, CuPc and ZnPc, respectively, and Pc(-2) is phthalocyanine dianion). Voltammetry shows that the reduction of nitrite occurs at potentials slightly less negative than for nitrate reduction. The MPc complexes lower the overpotential for the reduction of nitrite and nitrate as follows: CuPc > FePc > NiPc > CoPc > MnPc > ZnPc > glassy carbon electrode. The main product for the reduction of nitrite and nitrate is ammonia, with high yields of ammonia being obtained, depending on the choices of the electrolysis potential and MPc complex.