Photocatalytic Active Titania Thin Films through Oxidation of Metallic Ti in Aqueous H2O2 Solutions Containing Various Block Copolymers

摘要:

利用添加了嵌段共聚物P123、F127及硝酸的双氧水溶液直接氧化钛金属基体制备不同纳米形貌TiO2光催化薄膜。采用X射线衍射（XRD）、扫描电镜（SEM）、紫外-可见漫反射光谱（UV-Vis DRS）等技术分析样品的微观结构和形貌，以光催化降解若丹明B测定薄膜的光催化性能。结果表明，Ti-H2O2反应体系中仅添加嵌段共聚物的薄膜结晶呈树枝状，加入硝酸后薄膜形成纳米花结构。450 oC热处理后，薄膜为锐钛矿与金红石的混晶结构，平均晶粒尺寸在12~20 nm之间。薄膜的间接禁带宽度为2.65~2.85 eV，显著低于TiO2块体。添加P123获得的薄膜的光催化性能优于添加F127的薄膜。

Abstract:

Various nanostructured titania thin films were fabricated by direct oxidation of metallic Ti substrates in hydrogen peroxide solutions with the additives of nitric acid and block copolymers of P123 or F127. X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS) were utilized to analyze the morphology and structure of the titania films. Photocatalytic properties of the thin films were evaluated by the degradation of rhodamine B in water under the illumination of a high-pressure mercury lamp. The film only with the block copolymer additive consists of rod-like titania; while flower-like titania aggregates are achieved when both block copolymers and nitric acid are added to the hydrogen peroxide solution. After a subsequent calcination at 450 oC, all the titania films are crystallized further to a mixture of anatase and rutile with a similar average grain size. An indirect bandgap of 2.65-2.85 eV is estimated for the present films, which is significantly lower that of the bulk titania. The titania film derived with the P123 additive shows higher photocatalytic activity than that with the F127 additive, either with or without the additive of nitric acid.