蛋氨酸改性TiO2空心纳米盒高效可见光催化RhB分解和NO氧化

由高能面 TiO2纳米片 (TiO2-NSs) 组装成的 TiO2空心纳米盒 (TiO2-HNBs)显示出比单独 TiO2-NSs 更强的光催化性能, 但是 TiO2-HNBs 依然属于紫外光催化剂, 无法充分利用太阳能. 因此, 开发具有可见光响应的由高能面 TiO2-NSs 组装而成的 TiO2-HNBs 具有重要意义. 本文将立方体 TiOF2与含有 N 和 S 元素的生物分子蛋氨酸混合, 通过一步焙烧制备了具有可见光响应活性的 N 和 S 元素共掺杂的 TiO2-HNBs(掺杂催化剂标记为 TMx, 未掺杂催化剂标记为 Tx, x 代表焙烧温度).由立方体 TiOF2到锐钛矿相 TiO2空心纳米盒的转变是一个自模板转化过程. 氟离子的存在降低了 TiO2高能面(001)面的表面能, 从而使得高能面 TiO2纳米片的形成变得可能. 因此, 热处理立方体 TiOF2可得到由高能面 TiO2纳米片组装的 TiO2空心纳米盒.本文系统研究了焙烧温度 (300-500 ℃) 对所制 TiO2-HNBs 结构与光催化性能的影响. 结果发现, 在 350 ℃下焙烧, TiOF2完全转化成锐钛矿相 TiO2-HNBs. 但是焙烧蛋氨酸与 TiOF2的混合物, 需 400 ℃才能完全实现 TiOF2到锐钛矿相TiO2-HNBs 的转变. 这说明蛋氨酸的加入阻碍了 TiOF2向锐钛矿相 TiO2-HNBs 的转变. XPS 结果显示, 经过 400 ℃焙烧的蛋氨酸改性样品 (TM400), N 和 S 元素成功掺入了 TiO2-HNBs 晶格, 使其产生可见光催化活性.相对于 400 ℃焙烧 TiOF2所得样品 T400, 蛋氨酸改性的 TM400 催化剂可见光降解罗丹明 B 染料 (RhB) 和 NO 氧化的性能分别提升了 1.55 倍和 2.0 倍, 这与其更强的可见光吸收性能和光生载流子分离效率有关. 400 ℃焙烧的蛋氨酸改性的 TM400 可见光催化活性稳定, 连续 5 次可见光催化 RhB 降解后, 其活性没有明显改变, 显示了潜在的应用前景.

Enhanced visible photocatalytic activity of TiO2hollow boxes modified by methionine for RhB degradation and NO oxidation

Hierarchical TiO2hollow nanoboxes (TiO2-HNBs) assembled from TiO2nanosheets (TiO2-NSs) show improved photoreactivity when compared with the building blocks of discrete TiO2-NSs. However, TiO2-HNBs can only be excited by ultraviolet light. In this paper, visible-light-responsive N and S co-doped TiO2-HNBs were prepared by calcining the mixture of cubic TiOF2and methionine (C5H11NO2S), a N- and S-containing biomacromolecule. The effect of calcination temperature on the structure and performance of the TiO2-HNBs was systematically studied. It was found that methio-nine can prevent TiOF2-to-anatase TiO2phase transformation. Both N and S elements are doped into the lattice of TiO2-HNBs when the mixture of TiOF2and methionine undergoes calcination at 400 ℃, which is responsible for the visible-light response. When compared with that of pure 400 ℃-calcined TiO2-HNBs (T400), the photoreactivity of 400 ℃-calcined methionine-modified TiO2-HNBs (TM400) improves 1.53 times in photocatalytic degradation of rhodamine-B dye under visible irradiation (λ > 420 nm). The enhanced visible photoreactivity of methionine-modified TiO2-HNBs is also confirmed by photocatalytic oxidation of NO. The successful doping of N and S elements into the lattice of TiO2-HNBs, resulting in the improved light-harvesting ability and effi-cient separation of photo-generated electron-hole pairs, is responsible for the enhanced visible photocatalytic activity of methionine-modified TiO2-HNBs. The photoreactivity of methionine modi-fied TiO2-HNBs remains nearly unchanged even after being recycled five times, indicating its prom-ising use in practical applications.