Doping In ZnO Porous Nanoplates Applicable For Gas-Sensing

The rapid development of social economy and industrialization has improved people's quality of life on the one hand,but on the other hand a large amount of domestic and industrial gases and various volatile organic compounds(VOCs)have been released into the environment.Among them,VOCs are the most harmful atmospheric pollutants,which can cause environmental hazards(e.g.smog,photochemical pollution,etc.)and various diseases(e.g.respiratory difficulties,nerve damage,etc.).As the release of toxic and hazardous gases seriously endangers human health and social and environmental safety,there is an urgent need for effective monitoring of these gases.Gas sensors have been widely investigated for their low cost,high sensitivity and environmental friendliness.ZnO,as a typical metal oxide semiconductor,has promising applications in the detection of VOCs.However,the disadvantages of ZnO,such as low selectivity,high working temperature,and poor moisture resistance,have limited its practical application in gas sensing.Doping has important effects on the microscopic crystal structure,oxygen vacancy content,and forbidden band width of material,which can improve the sensing performance based on chemical and electronic sensing mechanisms.Therefore,based on the existing studies,low concentration Pt-doped ZnO nanoplates(NPs)and Co-doped ZnO NPs were prepared by one-step co-precipitation and hydrothermal methods,respectively,and used for gas sensing performance detection of acetone and benzenes(BTX),respectively,in this paper.1.Low concentration Pt-doped hydrozincite precursor was prepared by simple one-step co-precipitation method,which was then coated on alumina ceramic tubes to in-situ generate highly dispersed low concentration Pt-doped ZnO porous NPs during material aging.The Pt-doped ZnO porous NPs were used for gas sensing detection of acetone,and the results showed that the 0.01 mol%Pt-doped ZnO NPs exhibited excellent acetone sensing performance with an optimal working temperature of 400?.The as-prepared 0.01 mol%Pt-doped ZnO NPs sensor showed marked sensitivity toward acetone over 11 times higher than that of the pure ZnO sensor with a response value of 147.61.In addition,0.01%Pt-doped ZnO NPs sensor exhibited superior selectivity against other reference gases,and outstanding trace sensing capability(Ra/Rg=1.64 to 100 ppb).The prepared sensor also has good stability,durability,dynamic cycling,and resistance to humidity.The intrinsic mechanism for the improved gas sensing performance of ZnO NPs by low concentration Pt-doping may originate from the ultra-high dispersion state of Pt and the abundant oxygen species on the material surface.2.Using hydrozincite prepared by simple hydrothermal method as precursor,cobalt acetate was modified onto precursor material surface by impregnation,followed by washing,centrifugal separation,drying and calcination to obtain Co-doped ZnO porous NPs,which were used for gas sensing of four BTX gases.The obtained results showed that 3%Co-doped ZnO NPs significantly improved the response performance of four BTX gases with fast response/recovery speed and stable reproducibility compared with that of pure ZnO.The intrinsic mechanism of the improved gas sensing performance of Co-doped ZnO NPs for BTX may originate from the spillover and resistance modulation effects of Co and its own excellent catalytic degradation ability of pollutants.