Highly-improved room-temperature ppb-level NO2 gas sensors with oxygen vacancy-dominated In2O3/SnO2 n-n heterojunctions

Porous tremella-like In 2 O 3 /SnO 2 microspheres possess abundant oxygen vacancies. • In 2 O 3 /SnO 2 heterojunction narrows bandgap and enhances interfacial charge transfer. • In 2 O 3 /SnO 2 sensor shows ultra-sensitive ppb-level NO 2 detection performance at RT. • Superior RT NO 2 sensing performance stems from n-n heterojunction synergistic effects. • An intelligent sensing device based on the In 2 O 3 /SnO 2 sensor was built. The growing demand for ultra-sensitive, power-efficient NO 2 sensors in wearable and portable electronics has driven intense research, yet achieving reliable ppb-level detection at room temperature (RT) remains a major unresolved challenge. The In 2 O 3 /SnO 2 sensor overcomes this limitation through multiple synergistic effects arising from n-n heterojunction construction. The In 2 O 3 /SnO 2 heterojunction features a hierarchically porous morphology with larger specific surface area, enriched oxygen species and reduced E g . The In 2 O 3 /SnO 2 sensor displays outstanding NO 2 sensing performance with a response of 2209.77 toward 4 ppm NO 2 at RT, which is 250.82 times greater than that of the pristine In 2 O 3 sensor (8.81). More remarkably, the sensor realized an ultra-low theoretical limit of detection of 0.03 ppb, while still retaining a high response of 59.52 exposed to 500 ppb NO 2 . Moreover, the sensor demonstrated fast response/recovery kinetics, excellent selectivity, long-term stability, and remarkable humidity resistance. The superior performance is attributed to the multiple synergistic effects on morphological reconfiguration, bandgap narrowing, oxygen species enrichment, and vacancy-dominated unconventional charge transfer. An intelligent sensing device based on the In 2 O 3 /SnO 2 sensor was built with an innovative humidity compensation-based alarm logic, effectively reducing false alarms caused by humidity. This work provides new insights for the rational design of high-performance RT NO 2 sensors for practical applications. Download: Download high-res image (212KB) Download: Download full-size image