N,Cd TiO2光催化活性的实验与理论研究

 采用热分解法制备了N, Cd共掺杂纳米TiO₂光催化剂,通过XRD、XPS和UV-DRS等对样品进行了分析表征,并以甲基橙为目标降解物考察了其光催化性能。实验表明产物N, Cd TiO₂为锐钛矿型,颗粒约为10~15 nm,N取代了TiO₂晶格中的O原子,而Cd以游离态分布在TiO₂表面;其光吸收发生明显红移;光催化活性提高,N、Cd在提高TiO₂的光催化活性方面具有协同作用。采用第一性原理方法,对其电子结构和光学性质进行了理论计算。结果发现在N,Cd TiO₂的带隙中出现了N2p和Cd5s的杂质能级,价带的电子可以吸收较小的能量跃迁到杂质能级上,接着二次激发跃迁到导带上,电子跃迁变得容易,吸收波长向可见光区移动。计算结果很好地解释了实验现象。     

N/Zr共掺杂锐钛矿型TiO_2光催化协同作用机制的第一性原理研究

采用平面波超软赝势法计算了N,Zr单掺杂和共掺杂锐钛矿型TiO2的电子结构和光学性质.根据能量最低原理比较了不同替位掺杂构型的最稳定结构,而后分析单、共掺杂构型中各自的能带结构,通过计算态密度及分波态密度分析了其光学性质改善机制.此外通过分析体系的电荷密度图得出N与Zr有团簇成键的趋势.对不同掺杂体系的光学性质进行了对比分析,发现共掺杂方法可以有效增强TiO2材料对可见光的吸收以促进其更好的利用太阳能.本文的理论计算和分析将有助于理解共掺杂方法提高TiO2光催化效应的协同作用机制.     

第一性原理计算Zr/S共掺杂锐钛矿相TiO_2的电子结构

利用基于密度泛函理论的第一性原理平面波赝势方法对Zr/S共掺杂锐钛矿相TiO2的晶格参数、电荷布居、能带结构、电子分态密度和吸收光谱进行了计算.计算结果表明:Zr/S共掺杂导致锐钛矿相TiO2的晶格畸变使其体积变大,共掺杂时Zr和S的电荷布居数与单掺杂前的布居数略有不同;Zr/S共掺杂还导致锐钛矿相TiO2的禁带宽度变大0.1eV,达到2.30eV,但是由于Zr/S共掺杂在TiO2禁带之内引入了杂质能级,这些杂质能级可以作为电子跃迁的"台阶"而降低电子从价带跃迁到导带所需的激发光子能量,这有可能是实验上制备的Zr/S共掺杂TiO2具有较高光催化活性的内在原因.     

Al-N 共掺杂p 型ZnO 薄膜制备及电学性能的研究

利用射频磁控溅射技术在石英玻璃上制备了ZnO:Al薄膜,继而N离子注入实现薄膜的Al-N共掺杂,随后进行了不同温度和时间的热处理。并借助X射线衍射(XRD)、霍耳测试(Hall)、X射线光电能谱仪(XPS)等手段对ZnO薄膜的性能进行了表征。实验结果表明,Al-N共掺杂ZnO薄膜在578℃退火8 min表现出较稳定的p型导电,其载流子数高达1×1018～6×1018个·cm-3,对应的电阻率为1～9Ω·cm,迁移率为1～2 cm2·V-1·s-1。与单掺N相比,实现p型导电所需的退火温度有明显降低,这很可能与Al的掺入有关。此外,XPS测试结果证实大量的Ni取代O空位是薄膜p型导电的根本原因。     

Effects of Yb～(3 ) codoping on visible and near infrared emissions of Er～(3 )-Yb～(3 ) codoped Al_2O_3 powders by the sol-gel method

The 0.1 mol% Er3 and 0―2 mol% Yb3 codoped Al2O3 powders were prepared by the sol-gel method,and the phase structure,including only two crystalline types of doped Al2O3 phase,γ-(Al,Er,Yb)2O3 and θ-(Al,Er,Yb)2O3,was detected at the sintering temperature of 1000℃. The visible and near infrared emissions properties depended strongly on the Yb3 codoping,and the corresponding maximal peak intensities centered at about 523,545,660 and 1533 nm were obtained respectively for the 0.1 mol% Er3 and 0.5 mol% Yb3 codoped Al2O3 powders,which were composed of θ-(Al,Er,Yb)2O3 and a small amount of γ-(Al,Er,Yb)2O3 phases. The two-photon absorption process was responsible for the visible up-conversion emissions,and the one-photon absorption process was involved in the near infrared emissions of the Er3 -Yb3 codoped Al2O3 powders.     

可见光响应复合高效光催化剂的制备及应用

采用溶胶-凝胶法将过渡金属离子Fe和稀土离子Sm共掺杂改性纳米TiO2,首次将其负载在具有大比面积、微孔结构丰富的活性炭纤维载体上,制备出新型复合高效光催化剂。以甲基橙模拟染料废水为降解目标,考察催化剂的光催化活性。通过XRD、SEM、BET等手段表征其性质。结果表明:共掺杂改性复合光催化剂的光催化活性要明显优于空白炭纤维、纯二氧化钛负载活性炭纤维和单掺杂改性复合光催化剂的光催化活性,当煅烧温度500℃、n(Fe)∶n(Sm)∶n(Ti)为0.05∶0.1∶1、TiO2在活性炭纤维上的负载量为45%时,光催化效果最好;将光催化剂重复利用7次后,再次降解高质量浓度甲基橙溶液,降解率仍然超过95%;新型复合光催化剂对工业RO浓缩水中COD去除率可达37.12%。     

Effects of Yb^3＋ codoping on visible and near infrared emissions of Er^3＋-Yb^3＋ codoped Al2O3 powders by the sol-gel method

The 0.1 mol% Er^3＋ and 0-2 mol% Yb^3＋ codoped Al2O3 powders were prepared by the sol-gel method, and the phase structure, including only two crystalline types of doped Al2O3 phase, γ-（Al,Er, Yb）2O3 and θ-（Al,Er, Yb）2O3, was detected at the sintering temperature of 1000℃. The visible and near infrared emissions properties depended strongly on the Yb^3＋ codoping, and the corresponding maximal peak intensities centered at about 523, 545, 660 and 1533 nm were obtained respectively for the 0.1 mol% Er^3＋ and 0.5 mol% Yb^3＋ codoped Al2O3 powders, which were composed of θ-（Al,Er,Yb）2O3 and a small amount of γ-（Al,Er, Yb）2O3 phases. The two-photon absorption process was responsible for the visible up-conversion emissions, and the one-photon absorption process was involved in the near infrared emissions of the Er^3＋-yb^3＋ codoped Al2O3 powders.