Preparation Of WO₃-Cr₂O₃ Nanocomposite And Its Photoelectrocatalytic And Gas Sensing Properties

Metal oxide semiconductors have been widely studied in the field of photoelectrochemical water oxidation and gas sensor.The microstructure and physical properties of semiconductor determine the incident photonto-current efficiency and faradaic efficiency of water oxidation.Besides,it is also determined the sensitivity and selectivity of the gas sensor to the target gas.Especially,the p-n heterojunction semiconductor composite shows very good performance in the photoelectriccatalysis and gas sensing for the energy band match and the expansion of the electron depletion layer of semiconductor composite.Thus,in this paper,the main contents are as follows:?1?The WO₃ nanosheets-Cr₂O₃ nanoparticles?WO₃-Cr₂O₃?p-n heterojunction photoanode with high efficiency photoelectrochemical properties was prepared.The WO₃-Cr₂O₃ p-n heterojunction photoanode was prepared by electrophoretic method.Among them,the WO₃-Cr₂O₃ p-n heterojunction photoanode prepared by 10 s electrophoretic deposition showed the best photoelectrochemical performance.Compared to pure WO₃ photoanode under the same conditions,its onset potential decreased⁰.1 V and the photocurrent density increased to 2.57 times(1.8 mA cm^-2vs.0.7 mA cm^-2)at 1.8 V vs.RHE.Besides,the faradaic efficiency?holes to oxygen?increased from 73.9%to 92.0%.The mechanism of WO₃-Cr₂O₃ p-n heterojunction with significantly enhanced photoelectrochemical properties was summarized as follows:1)the energy band match and good interfacial contact of WO₃-Cr₂O₃ p-n heterojunction promote the separation and transfer of photogenerated electrons and holes,2)electronic reverse migration inhibited by the high density distribution of Cr₂O₃ nanoparticles that suppresses the side reactions in water oxidation.?2?The monoclinic WO₃ nanosheets-Cr₂O₃ nanoparticles?m-WO₃-Cr₂O₃?composite with enhanced gas sensitivity to butanone was prepared.The m-WO₃-Cr₂O₃ composite was prepared by hydrothermal method.When the molar ratios of W/Cr were 40:1 and 10:1,the response value of m-WO₃-Cr₂O₃ composite to100 ppm butanone at 180°C increases from 10.7?m-WO₃ nanosheets gas sensor?to40.5 and 38.2,respectively.Among them,the response and recovery time of m-WO₃-Cr₂O₃?W/Cr=40:1?to 5 ppm butanone at 180°C was only 9 s and 15 s,respectively.The mechanism of m-WO₃-Cr₂O₃ composite with enhanced gas sensor properties was the formation of p-n heterojunction leading to the expansion of the electron depletion layer,which leads to the enhancement of the sensitivity of sensors to butanone.In addition,Cr₂O₃ might have catalytic oxidation performance to butanone that maybe helpful to enhance the response to butanone.?3?The hexagonal WO₃ nanorods-Cr₂O₃ nanoparticles?h-WO₃-Cr₂O₃?composite was prepared and its gas sensor properties to butanone were discussed.The h-WO₃-Cr₂O₃ composite was prepared by hydrothermal method.When molar ratio of W/Cr is 10:1,the composite was successful to achieve the gas sensor selectivity to butanone at 205°C,and the response value to 100 ppm butanone was 5.4.The response and recovery time of h-WO₃-Cr₂O₃?W/Cr=10:1?composite to 5 ppm butanone is 10 s and 80 s,respectively.The mechanism of h-WO₃-Cr₂O₃ composite with enhanced gas sensor selectivity to butanone was the formation of p-n heterojunction and the catalytic oxidation of Cr₂O₃ to butanone.