Single-Phase Spinel High-Entropy (FeCoNiCrMn)₃O₄ Synthesized Using Electrospinning Technique and Its Application in the Sensing of Trimethylamine Gas at Room Temperature

High-entropy engineering strategies have achieved success in enhancing energy storage and catalytic performances but are rarely reported to improve gas-sensing dynamics, especially for room-temperature gas sensing. Herein, single-phase spinel high-entropy oxide (FeCoNiCrMn)3O4 has been synthesized by electrospinning and authenticated by XRD Rietveld refinement simulation, configuration entropy calculation, and element mapping. For the first time, the as-prepared alkalized high-entropy oxide (FeCoNiCrMn)3O4 shows room-temperature trimethylamine gas-sensing properties, including superior sensing response (113%), high gas selectivity, fast response/recovery speed (11 s/28 s), as well as preferable repeatability and reliability toward 500 ppm of trimethylamine gas. Gas-sensing tests of comparative samples obtained by replacing and reducing metal ions validate that the synergistic effect by Fe, Co, Ni, Cr, and Mn ions enables (FeCoNiCrMn)3O4 to exhibit room-temperature trimethylamine gas sensing, while more lattice distortion, adsorbed oxygen, and oxygen vacancies generated by alkalization treatment further heighten trimethylamine gas adsorption and catalyze surface gas-sensing reactions. The coupling of high entropy and alkalization strategy opens up a new path for improving room-temperature gas sensing.