Is entropy relevant to gas sensor? The case of spinel (CuCoNiCrMn)3O4 for NO2 detection

In recent years, high-entropy oxides (HEOs) have attracted significant attention owing to the synergistic effects arising from their multi-elemental structure. In this study, we investigate spinel (CuCoNiCrMn)3O4 HEO as a selective sensor for NO2. A comprehensive investigation of its crystal structure, micromorphology, elemental information, and gas sensing properties has been conducted. Gas sensor tests show that the (CuCoNiCrMn)3O4 HEO delivers a dramatic and selective response to NO2. To further explore the impact of entropy on sensor properties, medium-entropy Mn0.2Ni0.8Fe2O4, Ni0.99Co0.01Mn0.01Fe1.99O4 and low-entropy NiMn2O4 have also been synthesized and evaluated. Both experimental and density function theory studies demonstrate that the (CuCoNiCrMn)3O4 HEO exhibits superior sensing performance, attributable to enhanced charge transfer and significant orbital hybridization between Co atoms in (CuCoNiCrMn)3O4 HEO and O atoms in NO2. This work addresses the relationship between configuration entropy (ΔSconfig) and gas sensing properties, thereby advancing the exploration of HEO materials for high performance sensor applications.