Room-Temperature Trimethylamine Sensing of Spinel High-Entropy Oxide (FeCoCuCrMn)3O4 via Ultrafast Joule Heating

Abstract Revealing the interaction between sensing materials and gas molecules from the perspective of electronic orbital configuration is key to unlocking the selectivity origin of gas sensing. Herein, the single-phase spinel high-entropy oxide (HEO), (FeCoCuCrMn)3O4, has been synthesized via ultrafast Joule heating and exhibits high trimethylamine gas selectivity and sensing response at room temperature. Such gas-sensing dynamics originate from the fact that the eg sub-orbitals of Fe3+ 3d orbitals are highly matched with lone-pair electron orbitals of trimethylamine N atoms, enabling efficient hybridization to form stable Fe–N coordination bonds and constructing the atomic basis for high gas selectivity of (FeCoCuCrMn)3O4 toward trimethylamine. The appropriate lattice distortion induced by the ultrafast Joule heating strengthens orbital matching/hybridization, enhances trimethylamine molecule adsorption, and boosts electron transfer. The density functional theory (DFT) calculation of adsorption energy on Fe active sites, charge-density difference, and density of states validates the strong adsorption interaction and electron transfer of trimethylamine on (FeCoCuCrMn)3O4 surfaces. This study provides profound atomic-level insights into trimethylamine gas-sensing selectivity of HEOs.