模型催化剂VO_x/TiO_2(110)的高分辨电子能量损失谱研究

Abstract

模型催化研究能够更好认识催化过程,指导催化剂的合成.在TIO2(110)单晶上制备了VOX膜,采用俄歇电子能谱(AES)、低能电子衍射(lEEd)、高分辨电子能量损失谱(HrEElS)考察其结构和物理化学性质,及V-TIO2相互作用和热稳定性.结果表明,真空蒸着法制备的V/TIO2(110)界面发生明显的氧化还原作用,出现了VOX和低价TI,暴露O2后低价TI即被氧化回+4价,表面发生重构恢复到(1x1).在O2氛围中制备的VOX/TIO2(110)结构和V的价态会随覆盖度的增加发生变化,利用这种制备方法制备的VOX/TIO2(110)具有较多缺陷位,低温退火(≤600k)可使结构变得更规整.

Model catalyst study can help to understand the catalytic process,guide the synthesis of more efficient catalysts.The model catalysts comprised of V or vanadia deposited onto TiO2(110) surface was studied.The structure and physical chemistry properties of the VOx/TiO2(110),as well as the interaction between V and TiO2 and their thermal stability were investigated by high-resolution electron energy loss spectroscopy(HREELS),Auger electron spectrum(AES) and low energy electron diffraction(LEED).Deposition of metallic V onto TiO2(110) surface resulted in charge-transfer from V to TiO2 at the interface in which the V atoms were oxidized and the Ti4+ cations were reduced;when metallic V deposited was exposed to O2,Ti3+ was oxidized to Ti4+ again,and the structure of the surface restored.VOx/TiO2(110) produced by reactive evaporation under O2 atmosphere at room temperature may possess some defects,which would become a better ordered structure after annealing.The structure and valence of V changed with the increase of the coverage.