Preparation And Performance Studies Of Novel Three-dimensional Ordered Macroporous Indium Oxide Gas-sensitive Materials

Highly sensitive volatile organic compounds（VOCs）gas sensors have been developed for environmental monitoring.In₂O₃ is widely used in gas sensors due to its wide direct band gap and high electrical conductivity,but there are still problems such as high operating temperature,poor sensitivity and selectivity when using conventional In₂O₃ materials to fabricate gas sensors.Therefore,this paper uses both single-atom noble metal loading and rare earth element doping to modify In₂O₃ materials to improve their sensing performance for ethanol and formaldehyde gases,and explores the effects of changes in material composition and structure on their sensing performance and mechanism through a variety of characterization techniques.In the following details:1.Three-dimensional ordered macroporous（3DOM）In₂O₃ nanomaterials（x%Rh/In₂O₃）loaded with different levels of Rh were synthesized by the colloidal template method and UV photoreduction.ac-HAADF-STEM,CO-DRIFTS and XAFS analyses showed that Rh in 0.5%Rh/In₂O₃ existed in the atomic dispersion state that possesses a high number of active sites and adsorbed oxygen content.The sensor based on this material exhibited high sensitivity(53.01 ppm^-1)and ultra-low detection limits（0.07 ppb）for ethanol gas at 260℃,indicating that atomically dispersed Rh-loaded 3DOM In₂O₃ can significantly improve the sensing performance for ethanol gas while reducing the number of precious metals.Furthermore,the sensing mechanism of ethanol on the 0.5%Rh/In₂O₃ surface was investigated by Ethanol-DRIFTS and found to undergo a low activation energy（84.46 KJ/mol）ethanol-acetaldehyde-carbon dioxide gas-sensitive response pathway.2.3DOM In₂O₃ nanomaterials with different levels of Pr-doped rare earth elements（In₂O₃/x%Pr）were prepared by a one-step gel-crystal template method.XRD,Raman and XPS results show that Pr ions are successfully doped into the In₂O₃ material and inhibit In₂O₃ grain growth,leading to lattice distortion,increasing the oxygen vacancy defect content and the proportion of adsorbed oxygen in the material.UV-Vis DRS and Hall test results show that Pr doping narrows the electron leap band gap energy of the material,increases the Hall electron mobility and reduces the activation energy barrier during the reaction.The sensor based on In₂O₃/3%Pr material exhibited high sensitivity(3.37 ppm^-1),low detection limit（1.97 ppb）and high selectivity for formaldehyde gas at 240℃.