Efficient Cu-Co Dual-Site promotes selective catalytic oxidation of ammonia over cobalt based catalysts

Abstract

Selective catalytic oxidation of NH3 (NH3-SCO) into N2 and H2O is an efficient method to eliminate excessive NH3 emission from stock farming, agriculture, industrial sectors and NH3 slip in coal-fired power plants and diesel vehicles. However, it is a great challenge to develop the Co3O4 catalyst with high activity and high N2 selectivity at low temperature. Herein, a series of Cu doped Co3O4 catalysts is designed and synthesized, with discovering the role of Co-O bond strength by copper regulation in modulating oxygen vacancies and lattice oxygen to enhance the intrinsic activity and N2 selectivity of NH3-SCO. The Cu1Co2O4 catalyst (93 % NH3 conversion and 80 % N2 selectivity at 160 °C) achieves a higher catalytic performance compared with Co3O4 (78 % NH3 conversion and 50 % N2 selectivity at 160 °C). In addition, the N2 generation rate by normalizing over specific surface area for Cu1Co2O4 (13.1 μmol m-2h−1) is 1.7 times to that of Co3O4 (8.0 μmol m-2h−1), and the apparent activation energy of Cu1Co2O4 (36.7 kJ mol−1) is lower compared to that of Co3O4 (59.8 kJ mol−1). Reactive oxygen species and enhanced electron transfer promote the oxidation of NH3 to nitrate species, which can be further converted to N2 rather than N2O by remaining NH3 on the Cu site. The Cu-Co dual sites significantly contribute to the catalytic activity and N2 selectivity. This doping strategy is beneficial for the development of Co-O bond strength modulation in spinel catalyst and also provides a new idea for improving the NH3-SCO activity and N2 selectivity of Co-based spinel.