Rational design of spinel CoMn2O4 with Co-enriched surface as high-activity catalysts for NH3-SCO reaction

Abstract

Herein, we have successfully synthesized CoMn2O4 spinel (denoted as CMO-T) as high-performance catalysts for the selective catalytic oxidation of NH3 via a two-step precipitation and low-temperature (200 °C) annealing process. The large specific surface area, abundant defects, and a spinel structure with Co-enriched surface are obtained. The relationship between CoMn2O4 spinel structure and catalytic performance is found using multiple characterization techniques. The diffusion of Co3+ into the octahedral sites and formation of Co-enriched surface for CMO-T significantly enhance the redox ability of the catalyst, and increase NH3 chemical adsorption, resulting in the formation of more Lewis acid sites. Furthermore, the abundant defects can also shorten the metal-oxygen bond and result in the high mobility of oxygen species in CMO-T, which gives the positive effect for the catalytic activity of NH3 selective oxidation. Finally, an excellent NH3-SCO activity (T100 = 200 °C) and high catalytic stability are obtained on the synthesized CoMn2O4 spinel.