Development of visible light sensitive metal oxide photocatalysts having a functional accumulation properties by controlling surface structure

提出了一种将Fe^<3+>离子仅掺杂到硫或氮掺杂的TiO_2表面的新方法。在较宽的入射光波长范围内（包括紫外光和可见光），Fe^<3+>离子吸附在硫或氮掺杂的TiO_2上，对异丙醇的光催化氧化活性比未掺杂的TiO_2有明显的提高。当Fe^<3+>离子吸附量为0.90wt%时，光催化活性达到最大值。在Fe^<3+>离子掺杂的情况下，Fe^<3+>离子的最佳掺杂量为0.36wt%。当Fe^<3 +>离子含量大于1.0wt%时，S或N掺杂的TiO_2光催化剂上吸附的Fe^<3 +>离子的光催化活性逐渐下降。此外，当硫或氮掺杂的TiO_2光催化剂经NaBH_4还原后再经空气氧化后吸附Fe^<3+>离子后，其光催化活性进一步提高。 ...更多信息 在此条件下，Fe^<3+>在S和N掺杂TiO_2光催化剂表面的最佳吸附量分别为2.81和0.88 wt%。在处理过程中，吸附在S或N掺杂TiO_2上的Fe^<3+>离子被还原生成金属Fe，在曝气条件下Fe被再次氧化生成Fe^<3+>离子。改性后的SiO_2-TiO_2光催化剂（SiO_2-TiO_2）表面改性了烷基硅基团，如碳氢化合物、氟碳化合物、苯基等。结果表明，经表面改性的SiO_2-TiO_2催化剂对丙醛、己醛、壬醛、五氟苯甲醛和苯甲醛的氧化反应比未经表面改性的SiO_2-TiO_2催化剂有更好的催化效果。对于烃链修饰的SiO_2-TiO_2光催化剂，表面修饰的TiO_2光催化剂的光催化活性提高的一个重要因素是SiO_2-TiO_2光催化剂上引入的烷基硅基团与基质之间的疏水作用。苯基修饰的SiO_2-TiO_2光催化氧化苯甲醛的活性高于SiO_2-TiO_2-C_6。此外，五氟苯甲醛在SiO_2-TiO_2-C_8（F）链上的氧化比在SiO_2-TiO_2-C_8（F）链上更容易进行。这些结果表明，SiO_2-TiO_2表面引入的官能团在光催化氧化有机物的选择性中起着重要作用。少

A new method to dope Fe^<3+> ions only onto the surface of S-or N-doped TiO_2 is proposed. The photocatalytic activities of Fe^<3+> ions adsorbed on S-or N-doped TiO_2 photocatalysts for oxidation of 2-propanol are markedly improved compared to those of S-or N-doped TiO_2 without treatment of Fe^<3+> ions under a wide range of incident light wavelengths, including UV light and visible light. When the amount of Fe^<3+> ions adsorbed on S-doped TiO_2 particles was 0.90 wt%, photocatalytic activity reached maximum. In the case of N-doped TiO_2 with Fe^<3+> ions, the optimum amount of Fe^<3+> ions was 0.36 wt%. The photocatalytic activities of Fe^<3+> ions adsorbed on S-or N-doped TiO_2 photocatalysts decreased gradually when the amount of Fe^<3+> ions was greater than 1.0 wt%. In addition, when S-or N-doped TiO_2 photocatalysts adsorbed with Fe^<3+> ions was observed after reduction by NaBH_4 followed by air oxidation, further improvement in their photocatalytic activities were observed. … More In this case, the optimum amounts of Fe^<3+> adsorbed on the surfaces of S-and N-doped TiO_2 photocatalysts were 2.81 and 0.88 wt%, respectively. During the treatment, Fe^<3+> ions adsorbed on S-or N-doped TiO_2 were reduced to generate metal Fe, and Fe was reoxidized again to form Fe^<3+> ions under an aerated condition. After the treatment, the crystal structure of Fe^<3+> ions adsorbed on S-doped TiO_2 and adsorbtivity of 2-propanol on the photocatalyst were changed.Surfaces of SiO_2-covered TiO_2 photocatalysts (SiO_2-TiO_2) were modified with alkylsilyl groups such as hydrocarbon, fluorocarbon, and phenyl groups. Oxidation of propanal, hexanal, nonanal, pentafuluorobenzaldehyde, and benzaldehyde proceeded much more efficiently on the surface-modified SiO_2-TiO_2 particles than on SiO_2-TiO_2 photocatalysts without surface modification. In the case of SiO_2-TiO_2 photocatalysts modified with hydrocarbon chains, one of most important factors for improvement of the photocatalytic activities of surface-modified TiO_2 photocatalysts is the hydrophobic interaction between substrates and alkylsilyl groups introduced onto SiO_2-TiO_2 photocatalysts. SiO_2-TiO_2 modified with phenyl groups is more active in the photocatalytic oxidation of benzaldehyde than SiO_2-TiO_2-C_6. Furthermore, oxidation of pentafluorobenzaldehyde proceeded more favorably on SiO_2-TiO_2-C_8(F) chains than on SiO_2-TiO_2-C_8. These results indicated that the functional groups introduced onto the surface of SiO_2-TiO_2 play an important role in showing selectivity for photocatalytic oxidation of organic compounds. Less