are also revealed in the figure. These results confirm the successful synthesis of SnO2 of SnO2 -Pt-Pd-In2 O3 composite.
The morphology and the structure of the as-prepared SnO2- Pd-Pt-In2O3 composite were observed in the SEM images. The overall morphology of as-prepared composite is shown in Fig. 2(a) and (b). It can be seen that the composite has moderate agglom- eration. Furthermore, some loose nanoparticles disperse on the surfaces of composite, leading to coarse surfaces. The more detail structural features of as-prepared composite were examined by high-magnification SEM, as shown in Fig. 2(c) and (d). It can be noticed that the particles are generally irregular which are not uni- form in size and not well dispersed. However, the overall structure is fluffy. The fluffy structure is helpful for gas diffusion and its reac- tion on the surface of SnO2 -Pd-Pt-In2 O3 composite, so it is very important for the gas sensing performance of as-prepared SnO2- Pd-Pt-In2 O3 composite [28].