Selective Adsorption Response Of NiO-based Gas Sensor Based On P-n Junction Interface Control

As coke oven gas,water gas and other secondary gases,CO and H2 can be used as reactants in chemical and metallurgical production processes.However,due to the similar physical and chemical properties of CO and H2,it is difficult to distinguish the two gases in practical production and application,so it is impossible to realize the efficient utilization of chemical energy.Metal oxide semiconductor gas sensor has been widely studied and applied because of its advantages such as easy to carry,easy to operate,real-time monitoring,fast response-recovery time and high sensitivity.However,the poor selectivity of metal oxide semiconductor gas sensor restricts its application.Therefore,the development of metal oxide semiconductor gas sensor with excellent performance is extremely urgent.In this paper,Ni(CH₃COO)₂·4H₂O as nickel source was successfully prepared by sol-gel method combined with vacuum annealing technology.The composition and chemical valence of NiO were analyzed by XRD and XPS,and the existence of NiO material was confirmed.After gas sensitivity test on NiO material,it was found that under the condition of 550 ? annealing and 350 ? test temperature,the response values of NiO material to 400 ppm CO and H2 were 0.15 and 0.03,respectively.Compared with the other four different sintering temperatures and test temperatures,the response values of NiO material under this condition to CO and H2 were the largest difference.By loading 10 at% precious metal Pt,the response value of NiO material to CO and H2 can be increased to 1.8 times and 9 times of the original.In this paper,SnO₂ materials were prepared by sol-gel method,and n-x SnO₂/p-NiO composites were constructed by introducing SnO₂ materials into NiO materials.When x=0.59,n-0.59 SnO₂/p-NiO composites sintered at 550 ? can selectively detect CO and H2 at 400 ppm at 350 ?,and the response value for CO and H2 is 0.21 and-0.16 respectively.Under these conditions,n-x SnO₂/p-NiO composites can realize the selective detection of CO and H2 XRD and TEM analysis proved the composition of the composite material,and there were no other undesired elements except Ni,Sn and O.The results of EDS-mapping test showed that Ni,Sn and O were randomly distributed.The results of XPS test showed that Ni element existed in the form of Ni2+,and Sn in the form of Sn4+.TEM analysis results were consistent.Then,the stability and detection limit of n-0.59 SnO₂/p-NiO composite material were tested.It was found that the stability was good,and the detection limit of CO gas was below 100 ppm.Finally,the transition rule of n-0.59 SnO₂/p-NiO composite from n-type response to p-type response was found at different sintering temperatures and test temperatures.