Supplement 1

Preparation process of (FeCoNiCrMn)3O4 materials and procedure of gas sensing tests. XPS analysis of (FeCoNiCrMn)3O4. Raman spectroscopy of (FeCoNiCrMn)3O4. Comparison of NO2 sensing performances of various materials. Hall test results of (FeCoNiCrMn)3O4. Density functional theory calculations of (FeCoNiCrMn)3O4. The partial density of states of N, O atom in NO2 and Fe, Co, Ni, Cr, Mn atom in (FeCoNiCrMn)3O4. At different active metal sites, the adsorption energy and charge transfer between (FeCoNiCrMn)3O4 and NO2 with different adsorption configurations. At different active metal sites, the adsorption energy between (FeCoNiCrMn)3O4 and O2 with different adsorption configurations. The adsorption energy between FeMnO, FeNiO, FeCoNiO, FeMnCrO and NO2 with different adsorption configurations.