Visible Light-Activated Room Temperature NO 2 Gas Sensing Based on the In 2 O 3 @ZnO Heterostructure with a Hollow Microtube Structure

The persistent challenge of poor recovery characteristics of NO 2 sensors operated at room temperature remains significant. However, the development of In 2 O 3 -based gas sensing materials provides a promising approach to accelerate response and recovery for sub-ppm of NO 2 detection at room temperature. Herein, we propose a simple two-step method to synthesize a one-dimensional (1D) In 2 O 3 @ZnO heterostructure material with hollow microtubes, by coupling metal–organic frameworks (MOFs) (MIL-68 (In)) and zinc ions. Meanwhile, the In 2 O 3 @ZnO composite-based gas sensor exhibits superior sensitivity performance to NO 2 under visible light activation. The response value to 5 ppm of NO 2 at room temperature is as high as 1800, which is 35 times higher than that of the pure In 2 O 3 -based sensor. Additionally, the gas sensor based on the In 2 O 3 @ZnO heterostructure demonstrates a significantly reduced response/recovery time of 30 s/67 s compared to the sensor based on pure In 2 O 3 (74 s/235 s). The outstanding gas sensing properties of the In 2 O 3 @ZnO heterostructure-based sensors can be attributed to the enhanced photogenerated charge separation efficiency resulting from the heterostructure effect, and the improved receptor function toward NO 2, which can increase the reactive sites and gas adsorption capacity. In summary, this work proposes a low-cost and efficient method to synthesize a 1D heterostructure material with microtube structures, which can serve as a fundamental technique for developing high-performance room-temperature gas sensors.