Supplement information

Experimental synthesis and characterizations of the prepared materials; SEM and TEM images of the prepared materials; Schematic diagram of the sensor measurement system; Response of (CuCoNiCrMn)3O4 to 10ppm NO2 at room temperature; Response changes of (CuCoNiCrMn)3O4 sensor to 10 ppm NO2 at 175 {degree sign}C under different RH; The I-V curve of the sensor over the applied voltage range (-2 V) - (2 V); Two-dimensional diagram of the ΔSconfing corresponding to different elements; Repeatability test and response-recovery curves of NMCFO to CO and NO2; Comparison of NO2 sensors of different spinel oxides.