Highly Sensitive and Selective HCHO Sensor Based on Co Doped ZnO Hollow Microspheres Activated by UV Light

Low power consumption or even detecting harmful gases at room temperature is the future development trend of gas sensors. In this work, Co doped ZnO hollow microspheres were prepared by a facile water bath method. Co doping increases the electron density of ZnO and promotes the adsorption of oxygen on the surface. The surface band bending caused by oxygen adsorption further promotes the separation efficiency of photogenerated charge. The sensing results showed that 1.5 mol% Co doped ZnO exhibited the highest response of 111.6 to 50 ppm formaldehyde (HCHO) activated by UV light (6.8 mW/cm
²
) at room temperature. Moreover, the detection of limit can reach to 100 ppb, and the response and recovery time is 32 and 44 s, respectively. The excellent gas-sensing performance could be attributed to the increase in adsorbed negative oxygen species on the surface, the improved separation efficiency of photogenerated charge, and the porous and hollow microstructure of ZnO. In addition, the sensor possessed excellent reproducibility, selectivity, and a certain ability of moisture resistance.