An Ultra-Selective and Humidity-Resistant Room-Temperature-Operated NO

As a common gas-sensing material, TiO2 is limited by poor gas selectivity and humidity immunity like many other metal oxides. Here, an ultra-selective and humidity-resistant room temperature-operated NO2 sensor is developed using black TiO2 for the first time. Compared with conventional white TiO2, black TiO2 significantly enhances NO2 selectivity and humidity resistance by enhancing the NO2 response for ≥10 times while simultaneously suppressing responses to 7 common interfering gases and H2O adsorption. A wireless portable equipment is developed that exhibits the capabilities of identifying NO2 from a mixed atmosphere and recognizing environmental differences in practical scenarios. These improvements and different response types are attributed to the regulation of H2O adsorption: H2O layers are formed on white TiO2, leading to dominant ion-proton conductivity and blocked gas-solid interactions, while H2O adsorption is suppressed and hydroxyl groups are formed on black TiO2, enhancing NO2 response. This study not only promotes a significant advancement and proves the feasibility of using common metal oxides for high-performance NO2 detection at room temperature in a mixed environment irrespective of ambient humidity, but also offers valuable insights into the sensing mechanisms.