Synergistically improved formaldehyde gas sensing properties of SnO2 microspheres by indium and palladium co-doping

In/Pd co-doped SnO2, Pd-doped SnO2, In-doped SnO2 and pure SnO2 microspheres with a diameter of 500–600 nm were prepared by the one-pot hydrothermal method. Their structures and morphological characteristics were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). Their formaldehyde (HCHO) sensing properties were investigated in detail. Compared with the In-doped SnO2, Pd-doped SnO2 and pure SnO2 microspheres sensors, the In/Pd–SnO2 microspheres sensor exhibited excellent gas-sensing properties to HCHO gas and the operating temperature was relatively low. At the optimal operating temperature of 160 °C, the response of the sensor based on In/Pd–SnO2 microspheres to 100 ppm HCHO was 24.6 and the detectable HCHO minimum was effectively reduced to 5 ppm. In addition, due to In and Pd co-doping, the response and recovery time of the sensors to 100 ppm HCHO gas were diminished to 3 s and 6 s, respectively.