Synthesis of ZnO nanorods loaded with SnO2 cubes and the mechanism of improved ethanol sensing performance with DFT calculation

ZnO nanorods are synthesized by a simple calcination method. The SnO2/ZnO heterojunctions composed of ZnO nanorods and SnO2 cubes have been successfully constructed. The obtained samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS). The sensing performance has been tested in detail, and the results showed that 10%SnO2/ZnO exhibits excellent ethanol sensitivity at 300 °C. Compared to ZnO nanorods, the 10%SnO2/ZnO sensor not only decreased the operating temperature (400 °C–300 °C), but also increased response to ethanol by about three times. In addition, the sensing mechanism has also been simulated through density functional theory (DFT). The calculation results show that SnO2/ZnO exhibit greater adsorption energy (1.67 eV) for oxygen than that of ZnO (1.17 eV). Compared to the interaction between ZnO and ethanol (0.429 eV, 0.32e), SnO2/ZnO and ethanol exhibits greater adsorption energy (−1.11 eV) and more electron transfer (0.39 e). Therefore, the decreased operating temperature of 10%SnO2/ZnO sensor can be attributed to the synergistic catalytic effect of SnO2/ZnO on ethanol, and the improved response should be ascribed to more adsorbed oxygen and more electron transfer between ethanol and SnO2/ZnO heterojunction.