球磨处理的TiO_(2)光谱特征及其光催化性能研究

Research on Spectral Characteristics and Photocatalytic Properties of Ball Milled TiO_(2)

为改变TiO_(2)的颗粒尺寸和提高其光催化性能,采用高能球磨法处理TiO_(2)粉末,研究球磨时间对样品微观形貌、晶体结构、拉曼光谱、荧光光谱和光催化性能的影响;分析荧光光谱和光催化性能之间的关系,确定光催化机理为快速判断其光催化性能提供依据。结果表明:随着球磨时间的增加样品颗粒由规则形状变成无规则形状且表面变得粗糙。所有样品均主要为锐钛矿结构,有少量的金红石结构,随着球磨时间的增加金红石结构的(110)衍射峰逐渐增强说明在球磨过程中少量的TiO_(2)发生了相转变,晶粒尺寸先减小后增加。所有样品均出现锐钛矿型TiO_(2)拉曼散射峰,而未发现金红石晶型的拉曼散射峰。各个拉曼峰的半高宽随着球磨时间的增加都有所增加,这表明样品的表面质量下降,表面缺陷和氧空位逐渐增加导致。所有样品在470 nm附近均出现荧光峰,且球磨后的样品该荧光峰得到增强,经过球磨后的TiO_(2)样品在397,452,483,500和536 nm等处出现荧光峰,且球磨4 h后的TiO_(2)荧光峰强度最强,表明其表面缺陷和氧空位含量最多,与拉曼光谱分析结果是一致的。随着辐照时间的增加到100 min所有样品的降解率均有所提升且100 min后所有样品对甲基橙的降解率超过60%。经过球磨后的TiO_(2)样品的降解率都比未球磨的样品高,且球磨4 h的样品的降解率最高,表明其光催化性能最好。在光催化反应过程中,氧空位和缺陷成为俘获光生电子的中心,以致于光生电子与空穴的复合被有效地禁止。氧空位促使样品对氧气的吸收,氧气与氧空位俘获的光生电子发生相互作用而形成氧自由基,对有机物的氧化起到关键作用,因此表面缺陷和氧空位越多,即激子光致发光峰越强,其光催化性能越好。采用球磨法可提高TiO_(2)粉末的光催化性能,并通过激子光致发光峰的强弱可快速定性地判断光催化性能的表现。

In order to change the particle size of TiO_(2)and improve photocatalytic performance,TiO_(2)powder was treated by high-energy ball milling.The effects of ball milling time on the morphology,crystal structure,Raman spectrum,fluorescence spectrum and Photocatalytic Performance of the samples were studied;The relationship between fluorescence spectrum and photocatalytic performance was analyzed to identify the photocatalytic mechanism and provide a basis for quickly judging the photocatalytic performance of photocatalysts.The results showed that with the increase in milling time,the sample particles changed from regular to irregular shape,and the surface became rough.All samples were mainly anatase structures with a small amount of rutile structure.With the increase of ball milling time,the(110)diffraction peak of rutile structure gradually increased,indicating that a small amount of TiO_(2)had undergone phase transformation during ball milling,and the grain size first decreased and then increased.All samples showed the Raman scattering peak of anatase TiO_(2),but the Raman scattering peak of rutile crystal was not found.The FWHM of each Raman peak increased with milling time,indicating that the sample’s surface quality decreased,and the surface defects and oxygen vacancies gradually increased.All samples hada fluorescence peak near 470 nm,and the fluorescence peak of the samples after ball milling was enhanced.The TiO_(2)samples after ball milling had fluorescence peaks at 397,452,483,500 and 536 nm,and the intensity of TiO_(2)fluorescence peaks after ball milling for 4 h was the strongest,indicating that the surface defects and oxygen vacancy content were the most,which was consistent with the results of Raman spectroscopy.With the increase of irradiation time to 100 min,the degradation rate of all samples increased,and the degradation rate of methyl orange exceeded 60%after 100 min.The degradation rate of TiO_(2)samples after ball milling was higher than that without ball milling,and the degradation rate of samples milled for 4 hours was the highest,indicating that its photocatalytic performance was the best.In the photocatalytic reaction process,oxygen vacancies and defects became the center of capturing photogenerated electrons,so the recombination of photogenerated electrons and holes was effectively prohibited.The oxygen vacancy in the sample contributed to the absorption of oxygen.Oxygen interacted with photogenerated electrons captured by oxygen vacancies to form oxygen radicals,which played a key role in the oxidation of organic compounds.Therefore,the more oxygen vacancies and surface defects,the stronger the exciton photoluminescence peak,the better its photocatalytic performance.The photocatalytic performance of TiO_(2)powder can be improved by ball milling,and photocatalytic performance can be judged quickly and qualitatively by the intensity of exciton photoluminescence peak.