Humidity-Independent NO 2 Gas Sensors Based on CeO 2 /ZnO/WO 3 Heterostructure Films Fabricated by Template-Assisted Magnetron Sputtering

The detection of trace nitrogen dioxide (NO 2 ) in port atmospheres is crucial for protecting occupational health and maintaining air quality in coastal cities. Nonetheless, the reliable monitoring of NO 2 remains a challenge in complex environments featuring high humidity, diverse gas compositions, and dynamically fluctuating concentrations, which impose substantial interference. Here, the NO 2 sensors based on the CeO 2 /ZnO/WO 3 (CZWT) heterostructure films were fabricated via the template-assisted magnetron sputtering. The optimal device exhibited outstanding NO 2 sensing performance at 280 °C with high response (81.69 to 50 ppm NO 2 ), rapid response/recovery rate (25/10 s), ultralow detection limit (10 ppb), ideal selectivity, and excellent long-term stability (90 days). Further investigations suggested that the exceptional hydrophobicity of the CZWT heterostructure film and the dynamic Ce 3+ /Ce 4+ redox cycle endowed the sensors with humidity-tolerant response properties. In parallel, a wireless gas-detection device was developed to achieve the monitoring of NO 2 in humid environments. This work demonstrates an effective approach for designing humidity-independent MOS gas sensors.