Electrocatalytic, Homogeneous Ammonia Oxidation in Water to Nitrate and Nitrite with a Copper Complex

Abstract

Electrocatalytic ammonia oxidation (AO) at room temperature and pressure allows energy-economical and environmentally-friendly production of nitrites and nitrates. Few molecular catalysts, however, have been developed for this six- or eight-electron oxidation process. We now report [Cu(bipyalk)]+, a homogenous, earth-abundant metal electrocatalyst that realizes the title reaction in water. The complex selectively catalyzes the ammonia oxidation electrochemically at 94% Faradaic efficiency without generating the less-valuable N2 product commonly seen in molecular AO catalysis. Moreover, our complex is designed to not mediate water oxidation (WO), which is beneficial for high selectivity in AO in aqueous media. Initial mechanistic studies by electrochemistry propose monometallic catalysis and water or ammonia-nucleophilic attack for N–O bond formation. Figure 1