Study On The Photocatalytic Properties By Cerium Dioxide Based Composite Nanomaterials

Diuron as refractory pollutants are well-known to be present can exist in water and soil,which will cause significant pollution problem to the environment.Moreover,hydrogen has become a clean energy with great potential to alleviate the energy crisis due to its high calorific value of combustion,pollution-free and other environmentally-friendly characteristics.Photocatalytisis methods can be used to decompose pollutants into carbon dioxide and water.In addition,hydrogen can be produced via photocatalytic water splitting.CeO2 as one of semiconductors has been widely applied in diverse fields due to its abundant sources,non-toxicity,non-secondary pollution and high photocatalytic efficiency.However,it was only capable to be excited by incident light in the ultraviolet region due to the limitation of band gap energy,resulting in the low utilization rate of photon.Therefore,cerium oxide nanowires have been specifically prepared by a simple hydrothermal method.Then,the RGO-CNW,Cu-CNW and Cu-RGO-CNW were synthesized.The characterization methods of FE-SEM,FEG-TEM,XRD,FTIR,UV-Vis,EPR and PL were used to analyze the morphology and structure of the composite material.Furthermore,the effects of different experimental parameters(e.g.loading ratio,dosage,concentration,pH and sacrificial agent)were studied to quantitatively assess the performance of photocatalytic reavtions.In addition,the dynamic model and DFT model have been constructed to explore the reaction path and plausible mechanism of photocatalytic water splitting for hydrogen production,and degradation of diuron and 3,4-dichloroaniline.The findings were shown as follows:(1)According to the analysis of FE-SEM and FEG-TEM,the diameter of CNW in the composite was between 19 to 24 nm,which was the polycrystalline structure with smooth surface.Moreover,the comoposite materials have shown significant red shift and high efficiency photocurrent effect due t UV-Vis spectrographic inspection.The analysis of PL spectrum shows that loading RGO and Cu could effectively inhibit the recombination of photoelectron-hole,improving the utilization of photon.In addition,as Ce4+and Ce3+could exist simultaneously,oxygen vacancies caused by crystal surface defects can significantly enhance photocatalytic activity.(2)There was a positive correlation between the sacrificial agent and the polarity,and the same effect of the concentration of organic alcohol.When the volume of methanol was 20%,the highest hydrogen production rate was 2.976 mmol g-1 h-1 by 1Cu-2.5RGO-CNW.Indition,when initial concentration of pollutants was 5 mg L-1,the initial pH was 5,and the dosage of catalyst was 0.15 g mL-1,the highest removal rate of DCMU and DCA was 95.74%and 90.84%,respectively.Evidently,the three kinds of composite materials all owned better performance for material recycling.(3)The adsorption energy of adsorbed water molecules on CeO2(110)surface in the system were evaluated by DFT.The results could show that the composite material supported by RGO owned a stronger effect for the adsorption of water molecules.Compared with the position of Otop,Cu was more easily adsorbed by the position of Obri to form the stable structure.(4)It can be elucidated from the path of photocatalytic reaction,that Ce could be electron donor,and Cu and RGO can be electron transfer acceptor and capture trap,respectively.The methanol can be oxidized to form formaldehyde,and then carboxylation to consume the photogenerated holes,oxygen vacancies,free radicals and other oxidation groups.The aromatic rings and branched chain methyl groups are in the structure of DCMU molecular,which may be attacked and destroyed by the oxidative groups in the system.The chemical structure would be opened to be harmless small molecules by the effect of hydroxylation.Therefore,the cerium dioxide composites with high efficiency and stable photocatalytic activity were synthesized successfully herein.In addition,the structure of materials and the performance of photocatalytic have been also discussed in detail.This can provide a high efficiency,economy and stable method for photocatalytic technology to resolve the problems of environment and energy.