【作者】 何早阳；

【导师】 吕珺；

【作者基本信息】 合肥工业大学 ， 材料学， 2010， 硕士

【摘要】 纳米二氧化钛由于其独特的光催化特性,在废水处理、空气净化等领域得到了广泛的应用,但TiO₂光催化剂带隙较宽,对太阳能利用率很低。加之光生电子和光生空穴易于复合,光量子效率低,严重制约了TiO₂光催化的实际应用效率。通过在TiO₂材料中掺杂一些贵金属或非金属离子,可以提高TiO₂的可见光响应范围,从而达到提高光催化活性的目的。TiO₂的团聚和难以回收也是限制其应用的另一原因,将其负载于合适的基体上,是解决这一问题的有效方法。近年来,有关纳米二氧化钛掺杂及负载的研究,得到了广泛的关注。本文以云母为载体,TiCl₄为钛源,NaOH为沉淀剂,采用水解―沉淀法制备出了云母负载纳米TiO₂光催化剂（TiO₂/M）,研究了制备过程中温度、加料速率和浓度、粉体焙烧温度、光催化剂添加量,重复次数对光降解甲基橙活性的影响;同时分别以尿素为N源、Ag₂CO₃为Ag源,采用后掺杂法制得具有可见光响应的N掺杂TiO₂/M和Ag掺杂TiO₂/M。研究了N或Ag的掺杂对粉体中TiO₂晶相结构,粒度和光催化性能的影响。采用TG、XRD、XPS、SEM、EDS、DUV等对所制得的样品进行了表征,并以日光色镝灯为光源,甲基橙为模拟污染物检测其光催化活性。研究表明:绢云母与TiO₂通过桥氧相连形成均匀牢固的包覆层,样品中TiO₂物相为锐钛矿相和金红石相混晶,平均晶粒尺寸为10～30 nm,制备的TiO₂/M光催化剂对200～370 nm的紫外光有较高的吸收率,经400℃焙烧2h制备的光催化剂以5 g/L加入时,60 min对甲基橙的降解率达到44%;相同条件下重复利用三次,60 min对甲基橙的降解率仍然可高达28%;N或Ag的掺杂抑制了TiO₂晶粒的长大,减缓锐钛矿向金红石相的转变,同时N的掺杂形成Ti-O-N键,形成新的能级结构,使样品对光的吸收边红移至440～550 nm,具有明显的可见光响应,对甲基橙的光催化降解率与没有掺N的样品相比,最高可达1.6倍,N的掺杂能有效增加样品的使用寿命,相同条件下重复利用四次,光照60min对甲基橙的降解率仍然可高达43%;同时Ag的掺杂形成新的能级结构,随Ag⁺/Ti4⁺摩尔比的增加,样品对光的吸收边逐渐红移至440～520 nm,具有明显的可见光响应,当Ag⁺/Ti4⁺=0.05时,制得样品对甲基橙的光催化降解率是没有掺Ag的样品的1.5倍,相同条件下重复利用四次,该样品60 min对甲基橙的降解率仍然可达34%。更多还原

【Abstract】 Nano-TiO₂ photocatalytic material has been widely studied in the past years due to its attractive characteristics of long-term stability and nontoxicity. However, only a small portion of the solar energy can be utilized because the absorption edge of Nano-TiO₂ is below 380nm and the material shows photoactivity only under ultraviolet （UV） light. This is the one reason why nano-TiO₂ has not been widely used commercially. In recent years, theoretical and experimental studies have indicate that using non-metal or metal main group dopants, such as N and Ag, can greatly enhance the photoactivity of Nano-TiO₂ in the visible spectral range. For nano-TiO₂, easy to agglomerate and difficult to reuse is also another reason for restricting their application, using appropriate base to load the nano-TiO₂ is a good method to resolve this problem. Hence, many researches have been focused on the doping and loading.Using TiCl₄ as the source of titanium, NaOH as the precipitating agent, NanoTiO₂/mica photocatalyst （TiO₂/M） were prepared by the hydrolysis– precipitation method. The influence of the calcination temperature, adding amount and repetition of the degradation on photocatalytic activity about methyl orange were also discussed. N-doped or Ag-doped TiO₂/M samples with photocatalytic activity under visible light were directly prepared by hydrolysis-precipitation, where urea was the resource of N and Ag₂CO₃ was the resource of Ag ,respectively.The as-prepared samples were characterized by TG,XRD, XPS, SEM, EDSand DUV methods. The photocatalytic activity of the samples was tested by taking methyl orange as pollution models and using the solar dysprosium-color as light source.The results show that: The formation of TiO₂ film connected with the mica by bridging oxygen. The phases of as–produced powders are mixed crystal of anatase and rutile, the average grain size is from 10 nm to 30 nm. NanoTiO₂/mica photocatalyst shows high absorbtion of UV-light. Adding catalyst calcinated at 400℃for 2h with the concentration of 5 g/L, the degradation rate of methyl orange reaches 44% after 60 min; the degradation rate of methyl orange is still up to 28% when repeated this process three times under the same conditions. N-doping or Ag-doping could restrain the grain growth of TiO₂ and delay the phase transformation of anatase to rutile phase. N-doping formed a new energy level above the valence band of TiO₂ which can extended the adsorption edge to 440～550nm. The photocatalytic degradation rate of methyl orange can reached 1.6 times higher than those samples without N-doping. Ag-doping could also formed a new energy level above the valence band of TiO₂ which can extend the adsorption edge to 440～520nm, the photocatalytic degradation rate of methyl orange can reach 1.5 times higher than those samples without Ag-doping. The degradation rate of methyl orange can reach to 34% when this process was repeated four times under the same conditions.更多还原