Construction of Hybrid ZnO/SnO2 n–n Heterojunction with Hierarchical Porous Biomorphic Nanostructure as a High-Response Sensor for Methanol Gas

A novel hierarchical porous biomorphic ZnO/SnO was facilely synthesized in one step using bagasse as a bio-template. The structural features of the ZnO/SnO2 n–n heterostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results revealed that the as-prepared ZnO/SnO2 retained the original pore morphology of the bagasse material, and the ZnO/SnO2 was demonstrated with higher sensing performance as compared with the pure SnO2. Particularly, when the molar ratio of SnO2:ZnO = 1:1, the sensor displayed the highest response, showing an excellent response value of 37 under 100 ppm methanol at 340 °C. Meanwhile, the ZnO/SnO2 composite exhibited good gas selectivity and stability to methanol, which could mainly be attributed to the formation of n-n junctions between SnO2 and ZnO and the high capability of absorbed oxygen species of the ZnO/SnO2 composite.