ZnFe 2 O 4 Thin‐Film SO 2 Gas Sensor for Industrial Emission Monitoring in Petrochemical Refineries

Reliable detection of SO 2 at low operating temperatures remains a significant challenge for metal oxide gas sensors, particularly in harsh refinery environments where selectivity and stability are critical. In this study, ZnFe 2 O 4 thin films with compact and porous morphologies are deposited via spray pyrolysis to investigate their suitability for SO 2 sensing in refinery environments. The rigorous structural analysis reveals a strong correlation between crystalline features and sensing performance. In particular, an increased degree of spinel inversion enhances the sensor response by facilitating charge transport and surface reactivity. The porous films exhibit superior sensing behavior compared to compact films, owing to their higher surface area and increased availability of active adsorption sites. The optimized ZP375 sensor demonstrates a linear response towards SO 2 concentration up to 200 ppm, with a low detection limit of 0.41 ppm. The sensor exhibits optimal performance at an operating temperature of 150°C and demonstrates excellent selectivity towards SO 2 in the presence of other common interfering gases typically encountered in refinery environments. The sensor further exhibits long‐term stability extended up to 30 days. The results highlight the potential of spray‐deposited ZnFe 2 O 4 thin films as robust and energy‐efficient sensing materials for SO 2 monitoring in industrial emissions from petrochemical refineries.