Ultra-high gas sensing properties of porous Cr₂O₃@SnO₂ composite toward NO_x based on the p-p heterostructure

In recent years, environmental pollution and industrial accidents caused by the leakage of harmful gas are ever-increasing, and advanced gas sensors have been considered to be one of the main strategies for environmental monitoring and industrial safety control. Herein, Cr₂O₃ film decorated disordered porous SnO₂ (Cr₂O₃@SnO₂) composite was synthesized as an effective gas sensor toward NO_x gas. The response of the Cr₂O₃@SnO₂ gas sensor toward 100 ppm NO_x gas could reach 71 % and the response time is 2.5 s. Meanwhile, the minimum detection level toward NO_x gas is only 0.3 ppm, which is pretty lower compared to other materials reported before. The excellent gas-sensitive performance is attributed to the unique heterostructure formed between the Cr₂O₃ film and the SnO₂ matrix, and electrons in this area can migrate to overcome the barrier with less energy. As a result, O₂ and NO_x gas can draw electrons from the Cr₂O₃@SnO₂ gas sensor easily, thus leading to improved gas-sensitive performance. More importantly, this research provides a new idea to synthesize effective NO_x gas-sensitive materials based on the p-p heterostructure.