Humidity-Independent NO₂ Gas Sensors Based on CeO₂/ZnO/WO₃ Heterostructure Films Fabricated by Template-Assisted Magnetron Sputtering.

The detection of trace nitrogen dioxide (NO₂) in port atmospheres is crucial for protecting occupational health and maintaining air quality in coastal cities. Nonetheless, the reliable monitoring of NO₂ remains a challenge in complex environments featuring high humidity, diverse gas compositions, and dynamically fluctuating concentrations, which impose substantial interference. Here, the NO₂ sensors based on the CeO₂/ZnO/WO₃ (CZWT) heterostructure films were fabricated via the template-assisted magnetron sputtering. The optimal device exhibited outstanding NO₂ sensing performance at 280 °C with high response (81.69 to 50 ppm NO₂), 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 Ce³⁺/Ce⁴⁺ redox cycle endowed the sensors with humidity-tolerant response properties. In parallel, a wireless gas-detection device was developed to achieve the monitoring of NO₂ in humid environments. This work demonstrates an effective approach for designing humidity-independent MOS gas sensors.