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

CuMn 2 O 4 and CoMn 2 O 4 spinels were facilely synthesized by oxidation–precipitation and subsequent heat treatment at relatively low temperature. Selective catalytic reduction (SCR) of NO x demonstrates that NO x conversions in CuMn 2 O 4 with (111) plane (CuMn 2 O 4 -C) and in CuMn 2 O 4 -C with (311) plane (CuMn 2 O 4 -T) are more than 90% at 200 and 300 °C, respectively, which are superior to those in CoMn 2 O 4 -C and CoMn 2 O 4 -T. CuMn 2 O 4 -C and CoMn 2 O 4 -C exhibit higher absorption amounts of NH 3 /NO and more oxygen vacancies than CuMn 2 O 4 -T and CoMn 2 O 4 -T, respectively. In addition, CuMn 2 O 4 -C displays high catalytic activity and good stability in NH 3 -SCR in the presence of 100 ppm of SO 2 and 10 vol % H 2 O. In situ diffuse reflection infrared Fourier transform spectroscopy results indicate the coexistence of Eley–Rideal and Langmuir–Hinshelwood mechanisms in CuMn 2 O 4 -C, and the Eley–Rideal mechanism is predominant.