Investigation on gas sensing and temperature modulation properties of Ni2+ doped SnO2 materials to CO and H2

The metal oxide semiconductor sensors to quantify mixed gas components has been still difficult due to the poor selectivity although it has many advantages on application. To resolve this problem, the effect of doping on gas sensing performance was investigated. Simultaneous, PID (Proportional-Integral-Differential) temperature control technology was used to investigate the adsorption and desorption characteristics of H2 and CO by temperature modulation. The effect mechanism of Ni2+-doping and temperature-changing on adsorption-desorption of CO and H2 was proposed for distinguishing two difference. The result indicates that the responses of CO and H2 increased from 2.9 to 6.1 and 13.3 to 16.5, respectively with the increase of Ni2+ doping into SnO2, due to the increase of oxygen vacancies in gas sensing materials. It is found that the selectivity of CO to H2 was promoted nearly doubled with increase of Ni2+ doping amount to 4.0 mol% due to change of crystal structure. Temperature modulation test shows that with increases of Ni2+-doping and working temperature, the time to reach equilibrium for adsorption-desorption of gases decreased, which is considered to improve the surface activity of gas sensing materials. But the time for adsorption of the gases decreased with the increase of H2 content in the mixed gases, while the time for desorption of gases increased due to that H2 is easier to combine with adsorbed oxygen than CO. Based on the difference in adsorption and desorption in temperature-changing processes, it is a potential foundation for quantifying of CO and H2 in mixed gases by using metal oxide semiconduction sensor.