Construction And Gas Sensing Properties Of ZIF-67-derived CoOOH And Its Composite

With the development of science and technology,the amount of NOx toxic and harmful gas emitted from industrial and agricultural production has increased dramatically.It has a great impact on the ecological environment and human health.Therefore,it is necessary to design a real-time and efficient NOx gas sensor.In this paper,ZIF-67(8)was used as a precursor to synthesize CoOOH nanosheet by etching in NaOH solution.CoOOH/CuO and CoOOH/Ag composites were formed by compounding with CuO and noble metal Ag,and their gas-sensitive properties were investigated.The research content of this paper is as follows:CoOOH nanosheets with a thickness of 10-20 nm were formed by selecting a reasonable etching time and suitable Co and Zn molar ratio of ZIF-67(8)precursors by high concentration NaOH solution.The CoOOH nanosheets showed response values between 14.28 and 1.09 for 100-0.1 ppm NOx at room temperature,while it exhibited a good response(21.27)to 100 ppm ethanol at 150℃.Meanwhile,the material also has good selectivity and low detection limits.The enhanced gas-sensitive performance of CoOOH is due to a large number of oxygen vacancies,abundant pore channels and large specific surface area in the material,which promotes the adsorption and diffusion of gases in the material.CoOOH/CuO gas-sensitive sensing materials were prepared by adding different contents of Cu(NO3)2 during CoOOH preparation.The CoOOH/CuO nanosheets show high response of 21.2 to 100 ppm NOx and fast response time at room temperature.The enhanced gas sensing performance of CoOOH/CuO compared to pure CoOOH was attributed to the rich pore channels,the larger specific surface area(124.4 m2/g),and the formation of heterojunctions between CoOOH and CuO in the CoOOH/CuO composites,which exposed more active sites in the material.The CoOOH/Ag binary composites were synthesized by modification of noble metal Ag on the CoOOH,and the structural characterization and gas-sensitive properties of CoOOH/Ag composites were investigated.The response value of CoOOH/Ag for 100 ppm NOx was 33.2 at room temperature,about 2.3 times higher than that of CoOOH,and has good reproducibility.The gas-sensitive properties of the CoOOH/Ag composites were further improved compared to that of CoOOH.This is attributed to the better catalytic properties and spillover effect of the noble metal Ag which facilitates the increase of the chemisorbed oxygen content in the material.