Hierarchical Porous In2O3/ZnO Heterojunctions with Oxygen Vacancy Enrichment for Ultrasensitive Ethylene Glycol Detection

Abstract The growing demand for real-time monitoring of toxic ethylene glycol (EG) vapor in industrial safety and energy storage systems calls for high-performance gas sensors with superior sensitivity. Herein, hierarchically porous In2O3/ZnO heterojunctions were constructed by anchoring ZIF-8-derived ZnO onto nanoflower-like In2O3 through a low-temperature conversion strategy. The indium-containing precursor promoted ZnO crystallization at 350 °C, enabling mild heterojunction formation. The optimized In2O3-2ZnO exhibited the largest specific surface area, the highest concentration of oxygen vacancies, and a narrowed bandgap. Accordingly, In2O3-2ZnO delivered a response of 1077.92 ± 40.65 toward 20 ppm EG at 200 °C, with a theoretical detection limit of 105 ppb, excellent selectivity, good repeatability, and stable long-term performance. The enhanced performance originates from the combined effects of oxygen-vacancy-assisted oxygen activation and In2O3/ZnO interfacial electronic modulation, which strengthen EG adsorption and charge-transfer-induced resistance variation. The low ppb-level detection limit suggests its potential for early warning of EG leakage before hazardous accumulation in battery thermal management and industrial cooling systems.