Structure–Activity Relationships of AMn2O4 (A = Cu and Co) Spinels in Selective Catalytic Reduction of NOx: Experimental and Theoretical Study

CuMn2O4 and CoMn2O4 spinels were facilely synthesized by oxidation–precipitation and subsequent heat treatment at relatively low temperature. Selective catalytic reduction (SCR) of NOx demonstrates that NOx conversions in CuMn2O4 with (111) plane (CuMn2O4-C) and in CuMn2O4-C with (311) plane (CuMn2O4-T) are more than 90% at 200 and 300 °C, respectively, which are superior to those in CoMn2O4-C and CoMn2O4-T. CuMn2O4-C and CoMn2O4-C exhibit higher absorption amounts of NH3/NO and more oxygen vacancies than CuMn2O4-T and CoMn2O4-T, respectively. In addition, CuMn2O4-C displays high catalytic activity and good stability in NH3-SCR in the presence of 100 ppm of SO2 and 10 vol % H2O. In situ diffuse reflection infrared Fourier transform spectroscopy results indicate the coexistence of Eley–Rideal and Langmuir–Hinshelwood mechanisms in CuMn2O4-C, and the Eley–Rideal mechanism is predominant.