Sea urchin-like SnO2/α-Fe2O3 heterostructural microspheres for enhanced acetone gas sensing: Materials preparation, performance evaluation, and mechanism investigation

Herein, sea urchin-like SnO2/α-Fe2O3 (SU-SnO2/α-Fe2O3) heterostructural microspheres was prepared successfully by two-steps hydrothermal treatment, and used as semiconductor for acetone gas sensing. SEM and TEM characterizations showed that as-prepared composites exhibited sea urchin-like morphology with microstructures of inner SnO2 microspheres and outer vertically grown α-Fe2O3 nanorods. SnO2/α-Fe2O3 microspheres presented higher and faster response / recovery for acetone in comparison to pure SnO2. At the optimum temperature of 300 °C, response value of SU-SnO2/α-Fe2O3 sensor reached 18.7 towards acetone vapor with concentration of 100 ppm. The response time was 8 s, and recovery time was 2 s. Moreover, the proposed method displayed an excellent linearity for measuring acetone vapor with concentration range of 1–200 ppm. The improvement of gas sensing properties for SnO2/α-Fe2O3 microspheres was ascribed to the unique microstructures, formation of heterojunction, and abundant adsorbed oxygen. To further demonstrate the promoted mechanism, adsorption behavior of as-prepared composites for acetone molecule was investigated by density-functional theory (DFT), with results that Fe sites on the hetero-interface possessed strong interaction with acetone molecule, which enhanced the gas sensing properties towards acetone. This study confirmed the gas sensor performance of SnO2/α-Fe2O3 microspheres towards acetone, and supplemented the promotion mechanism by DFT calculations.