Preparation And Photocatalytic Properties Of Noble Metals Modified TiO₂ Nanocrystals Assembled Porous Structures

In recent years,photocatalysis has got widely attention because of its potential of solar energy conversion,as a "green" advanced oxidation technology,has been widely used in sewage treatment and air purification,etc.Titanium dioxide nanomaterials because of its excellent performance and high potential have been widely studied in recent years and applied to photocatalytic environmental protection.The crystal structure,crystal phase,specific surface area and porosity of TiO₂ nanomaterials affect the photocatalytic property,and the different morphology is a large influence factor for the performance of TiO₂,such as nanomicrospheres,nanorods,nanowires,nanoflowers,especially three-dimensional nanoflowers morphology,due to its large specific surface area and porous structure has a significant effect on the performance of the titanium dioxide.However because of the widely band gap of TiO₂?3.2 eV?,the recombination rate of photogenerated-electron-hole pairs is higher,which limits its application in the field of photocatalysis.Therefore so many scholars devoted theirself to research the modification method.It is commonly used modification method have noble metals deposition,non-metallic elements doping,narrow gap semiconductor compound,dye sensitization,and so on.In the paper we use TiO₂ as the matrix and modified with noble metal Au nanoparticles,through prepared different shape of titanium dioxide and then modified Au nanoparticles,respectively.Using SEM,TEM,XRD,UV-vis and PL to characterize the as-prepared samples,and evaluated samples performance by degrading organic pollutants of rhodamine B solution under the simulated sunlight.Finally,the effect of morphologies and the different mass ratio of gold on the photocatalytic property of the samples were compared.The following results are obtained:?1?Three-dimensional porous flowerlike anatase Ti O2 was prepared by hydrothermal method with tetrabutyl titanate as titanium source,ethylene glycol as solvent,sodium hydroxide solution?1 mol/L?as precipitant,and studied the effect of different hydrothermal temperature on the morphology of the prepared TiO₂.The prepared flowerlike TiO₂ has an uniform morphology and excellent dispersibility,the lamellar thickness of flowerlike is about 20-25 nm,the samples were characterized by various methods.We found that the prepared pure phase flowerlike Ti O2 has a better photocatalytic degradation ability than P25.?2?Noble metal Au modified TiO₂ composite photocatalyst was prepared through one-step hydrothermal method using tetrabutyl titanate,ethylene glycol,sodium hydroxide solution?1 mol/L?,HAuCl4·4H2O?1 mmol/L?as raw material.The experiment studied different mass ratio of gold effect on morphology and photocatalytic properties of samples.The results show that the gold mass ratio is 5 wt% and the as-prepared product has the most regular morphology and the best photocatalytic degradation efficiency.?3?With tetrabutyl titanate as titanium source,ethanol as solvent,HAuCl4·4H2O?1 mmol/L?as noble metal source.First,by controlling tetrabutyl titanate dropping rate prepared good morphology of nanocrystal assembled flowerlike TiO₂,and Au modified flowerlike TiO₂ composite photocatalyst was prepared through the photoreduction deposition method,then the influence of morphology and photocatalytic performance of the samples with different mass ratio was studied.The results show the morphology of Ti O2 was the best when the tetrabutyl titanate dropwise added into ethanol,and has the best photocatalytic performance when the mass ratio is 5 wt%.Finally,the photocatalytic property effect of different solvents on the preparation of titanium dioxide and different methods to prepare composite were compared.The results show the ethanol as the solvent to prepare titanium dioxide has a better photocatalytic property and noble metal Au modified TiO₂ composite samples was prepared by one-step hydrothermal method has better photocatalytic properties.