Preparation, Characterization And Performance For Oxidation CO Of CuO Mesoporous Nanosheets

CO as a pollutant produced by incomplete combustion of fossil energy,not only pollutes the environment,but also endangers human health.At present,there are three common methods of CO treatment:adsorption,photocatalysis and thermal catalysis.The performance of adsorption method is unstable and easy to produce secondary pollution after repeated used,photocatalytic method can only be excited by ultraviolet and visible light,so the utilization rate of light energy is low.The application of thermal catalysis is limited by the use of noble metal catalysts.In recent years,the developed photocatalytic method combines the advantages of photocatalysis and thermal catalysis.It not only utilizes clean and renewable solar energy,but also reduces the energy consumption required in the process of thermal catalysis,so it is a feasible method for CO treatment.Therefore,it is of great significance to develop a cheap and efficient catalyst for CO.Based on this,the CuO nanoparticles?CuO-60,CuO-80,CuO-90?were prepared at 60 ?,80 ?,90? and the properties of the thermal catalytic oxidation of carbon monoxide?CO?were studied.CuO mesoporous nanoparticles?expressed as CuO-MNSN?were prepared at room temperature of 25 ?.The effects of CuO-MNS on CO thermal catalysis,photocatalytic activity,catalytic activity and catalytic principle were studied.The main contents and results are as follows:?1?CuO nanosheets?denoted as CuO-60,CuO-80,CuO-90 respectively?were prepared from CuSO₄·5H₂O,NH₃·H₂O and NaOH by a simple method which was placed in a thermostatic water bath at 60?,80?,90?,respectively.It is found that the temperature of water bath reaction has an important effect on the thermal catalytic oxidation of CO on the prepared CuO nanoparticles.With the increase of reaction temperature,the thermal catalytic oxidation activity of CuO nanoparticles decreased.The thermal catalytic activity of the three was compared in the following order:CuO-60>CuO-80>CuO-90.The CO₂ yield of CuO-60 at 140? is 5.2 times of that of CuO-90.The results show that the order of lattice oxygen activity among them is CuO-60>CuO-80>CuO-90.Therefore,the order of thermal catalytic activity in dark state is CuO-60>CuO-80>CuO-90.The results showed that the thermal catalytic activity of the three systems was significantly stronger than that of the dark state conditions?CO-TPR and O₂-TPO?.It was proved that illumination accelerated the second step of the CO reaction catalyzed by CuO as the catalyst.Therefore,the thermal catalytic activity under illumination is stronger than that under dark state.?2?CuO mesoporous nanosheets?denoted as CuO-MNS?were prepared from CuSO₄·5H₂O,NH₃·H₂O and NaOH by a simple method which was placed in a thermostatic water bath at 25?.CuO-MNS has very efficient photothermal catalytic activity and excellent stability for the toxic air pollutant CO under the full solar spectrum of the Xe lamp.Compared to commercial nonporous CuO and TiO₂?P25?,the photothermocatalytic activity of CuO-MNS under the Xe lamp illumination is enhanced by 19.8 and 88.7 times,respectively.Under the UV-vis-IR illumination with the same light intensity,the photothermocatalytic activity of CuO-MNS is 331 times higher than P25 conventional photocatalytic activity.CuO-MNS also demonstrates effective photothermocatalytic activity even under the?>830 nm infrared illumination.?3?It is discovered that the greatly effective photothermocatalytic activity of CuO-MNS is attributed to effective solar-light-driven?SLD?thermocatalytic CO oxidation.It was found that the highly efficient photothermocatalytic activity of CuO-MNS catalysts originated that the heat samples conversed by absorbing light energy was enough to make their surface temperatures reach light-off temperature(T_light-off),thusdrivingthermalreaction.MeasurementsofCO temperature-programmed reduction?CO-TPR?experiment,Raman spectra and density functional theory?DFT?calculations show that mesoporous formation significantly increases the activity of CuO lattice oxygen and the number of active lattice oxygen,and contributes to the obvious enhancement of CuO thermal catalytic activity.a novel photoactivation,completely unlike the well-known photocatalysis of photocatalytic semiconductors such as TiO₂,is discovered to considerably promote the SLD thermocatalytic CO oxidation on CuO-MNS.By combining the experimental evidence of CO-TPR and O₂-TPO in the dark and under the Xe lamp illumination as well as the theoretical evidence by the DFT calculations in the ground state and excited state,we reveal the origin of the novel photoactivation:the Xe lamp illumination considerably promotes the re-oxidation of the pre-reduced CuO-MNS,thus considerably enhancing the catalytic activity of CuO-MNS.