Structural Regulation And Gas Sensitivity Performance Studies Of Cobalt Tetroxide

Co3O4 is a typical p-type semiconductor gas sensing material.How to effectively improve the gas-sensing performance of Co3O4 material is a hot spot for reserchers.In this paper,rod-shaped Co3O4 materials and K-doped Co3O4 materials were prepared by surfactant with the help of hydrothermal method.The structure and chemical composition of the materials were studied in detail by means of characterization.The doping of K improves the gas-sensing performance of the material by adjusting the content of Co3+ and O2-active substances on the surface of the material.The study further infers the gas-sensing mechanism of the doped material.The details are as follows:(1)In the experiment,hydrothermal method was used to successfully prepare rod-shaped Co3O4 materials by adjusting the amount of surfactant cetyltrimethylammonium bromide(CTAB)and the calcination temperature of the precursor.Analysis of phase morphology and crystal structure revealed that rod-shaped Co3O4 was evenly distributed,and the degree of lattice distortion was positively correlated with the gas-sensing performance of the material.The response of the gas sensor to 50 ppm C2H5OH at the optimal operating temperature of 170? can reach 56,and the response/recovery time is 365 s/128 s.Studies have shown that the crystallinity of the material becomes worse when the calcination temperature is lower,resulting in increased defects and increased oxygen content on the surface,which in turn increases the gas-sensing response.In addition,the sensor has a low detection limit(0.005 ppm)and good stability and repeatability,but the selectivity of VOCs gas needs to be improved.(2)Using the same hydrothermal method,K-doped rod-shaped Co3O4 materials were prepared,and the gas-sensitivity properties of Co3O4 materials with different doping amounts to C2H5OH were tested.Crystal phase and chemical analysis results show that the ratio of Co3+ to Co2+on the surface of 1.0%doped K-Co3O4 material is the highest,and the surface oxygen vacancy content is also the largest.These two factors contribute to the high content of chemically adsorbed oxygen on the surface of the material,which effectively reduces the forbidden band width of the crystalline semiconductor,so that the material has a larger carrier concentration at a lower operating temperature.In addition,most of the Co3+active sites promote the cracking and oxidation of C2H5OH molecules,thereby accelerating the response-recovery speed of the interaction between the material and the detection gas.Gas sensitivity performance results show that the best working temperature of K-doped rod-shaped Co3O4 gas sensor is 160?,and the response value of 1.0%K-Co3O4 sensor to 50 ppm C2H5OH can reach 220,which is 6 times higher than pure Co3O4.At the same time,the material also has good selectivity,repeatability and long-term stability.The excellent gas-sensing performance makes this material expected to be used in the actual detection of VOCs.