Interfacial oxygen vacancies and energy-level engineering on CeO2-PPy-rGO nanocomposites towards boosted NO2 sensor performance

Monitoring of harmful nitrogen dioxide (NO2) gases is imperative for our health and environmental protection. The room-temperature operating NO2 gas sensors still suffer a limited sensitivity and slow response/recovery rate. In this work, novel CeO2-PPy-rGO nanocomposites were synthesized for improved NO2 sensing performance. The decoration of rGO introduced additional oxygen vacancies on CeO2 for enhancing the sensor response. PPy acted as a buffer layer of energy level connecting CeO2 and rGO components and promoted the response and recovery rate. The designed sensor demonstrated ppb-level NO2 detection in p-type sensing behaviors with rapid response/recovery characteristics as expected at room temperature (RT). The hybrid sensor also showed excellent selectivity, long-term stability and extremely low detection limit toward NO2. The significantly enhanced sensing properties to NO2 could be attributed to activity enhancement, a gently gradient energy level and π-π stacking between rGO and PPy. This study offers a perspective on the design of CeO2-based gas sensors for NO2 detection at RT.