Development of Highly Visible-light Sensitive Photocatalyst by Controlling Surface Nano-structure of TiO_2 with Cold Plasma Treatments

采用磁控管式冷等离子体反应器，对由二氧化钛颗粒组成的薄膜进行了Ar和N等离子体串联处理。X射线衍射仪分析表明，掺氮增加了锐钛矿(101)晶面的半宽，掺氮使锐钛矿的晶格发生了明显的扭曲。这种晶格扭曲是由Ti-N键和氧缺陷的形成引起的。等离子体处理的薄膜除了紫外光吸收外，还表现出可见光吸收。出现可见光活动，与可见光吸收相对应。可见光活性的出现源于Ti-N键的形成。根据对掺氮二氧化钛能带结构的理论分析，钛氮键的形成足以使可见光活性二氧化钛的带隙变窄，要获得最高的可见光活性，最佳的钛氮键含量是必要的。钛氮键的大量过剩会导致氧缺陷的增加，从而抑制粒子的可见光活性。本工作表明，冷等离子体处理可以控制二氧化钛粒子的表面纳米结构。冷等离子体处理有可能加速Ti-N键的形成，抑制颗粒中氧缺陷的形成，并通过颗粒中可见光活性的出现来开发高灵敏的光催化剂。

A film composed of TiO_2 particles was treated with argon and nitrogen plasmas, in series, with magnetron-type cold plasma reactor. According to XRD analysis, half-value width of anatase (101) plane was increased with nitrogen-doping and it becomes apparent that crystal lattice of anatase was distorted with nitrogen-doping. Such lattice distortion will be originated with formations of Ti-N bonds and oxygen defects.The plasma-treated film revealed visible-light absorption, in addition to ultraviolet-light absorption. Visible-light activity appeared, corresponding to the visible-light absorption. The appearance of the visible-light activity will be originated by the formation of Ti-N bonds. According to theoretical analysis of band structure for the nitrogen-doped TiO_2, the formation of Ti-N bonds will be adequate for narrowing of the band gap in the visible-light active TiO_2. Optimum content of Ti-N bonds is necessary to obtain the highest visible-light activity. A large excess of Ti-N bonds will bring about an increase in oxygen defects which depress the visible-light activity of the particles.In this work, it becomes apparent that surface nano-structure of TiO_2 particles can be controlled by the cold plasma treatments. It is possible by the cold plasma treatments to accelerate the formation of Ti-N bonds and depress the formation of the oxygen defects in the particles, and highly sensitive photocatalyst can be developed by the appearance of the visible-light activity in the particles.