氧化石墨烯改質二氧化鈦光觸媒提升染料降解效率之研究

Improving Dye Degradation Efficiency with Graphene Oxide-Modified Titanium Dioxide Photocatalyst

二氧化鈦光觸媒因寬能隙特性，必須於紫外光下才具有光催化活性，且激發後產生的電子與電洞對易複合性質，導致在應用上受到限制。為了有效提升環境上的應用，本研究以氧化石墨烯（Graphene Oxide, GO）改質二氧化鈦光觸媒，於不同種類（GOA及GOB）及添加比例（1%~4%）下合成二氧化鈦/氧化氧化石墨烯光觸媒複合材料。經由場發射電子顯微鏡（Field Emission Scanning Electron Microscope, FE-SEM）和穿透式電子顯微鏡（Transmission Electron Microscope, TEM）觀察，本研究已成功合成二氧化鈦/氧化石墨烯複合材料；從X光繞射儀（X-ray diffraction , XRD）晶相分析，添加氧化石墨烯對於二氧化鈦晶相不會產生變化；於傅立葉轉換紅外光譜儀（Fourier-Transform Infrared, FTIR）分析，改質複合材料表面產生Ti-O-C與Ti-O-Ti之官能基，證明氧化石墨烯與二氧化鈦之間具有相對應之化學鍵結；紫外可見光光譜儀（Ultraviolet–Visible spectroscopy, UV-Vis）吸收光譜分析，添加氧化石墨烯可降低二氧化鈦之能隙，從3.08 eV降至2.42~2.83 eV之間。於光催化試驗中，於紫外光下降解亞甲基藍（MB）染料廢水得知，T4GOA光觸媒僅需30分鐘即可達到100%之降解，相較於未改質二氧化鈦光觸媒可有效提升約38%降解效率，反應速率常數從4.506×10-2 min-1顯著提升至1.693×10-1min-1；另在可見光下降解染料廢水發現，以氧化石墨烯改質光觸媒複合材料降解效率皆高於未改質二氧化鈦光觸媒，同樣以T4GOA光觸媒具有較佳的光催化效果，證實本研究以氧化石墨烯改質二氧化鈦光觸媒材料提升染料降解效率之可行性。

Titanium dioxide photocatalyst exhibits photocatalytic activity only under UV light due to its high band gap, and the excited electron and hole pairs are prone to recombine. The re-combination restricts its use. To delay the recombination of electron and hole pairs and to increase its environmental applications, a titanium dioxide/graphene photocatalyst composite with various kinds（GOA and GOB）and addition ratios（1%~4%）are synthesized in this study. The primary aims of doping graphene are to decrease the band gap, increase the adsorption capacity of the photocatalyst, and inhibit the recombination of electron-hole pairs to enhance photocatalytic efficiency. Through FE-SEM and TEM photograph observation, this study successfully synthesizes titanium dioxide/graphene photocatalyst composite. Based on XRD spectrum analysis, adding graphene will not change the crystal structure of titanium dioxide. By virtue of FTIR functional group analysis, it is proven that graphene has a corresponding chemical bond with titanium dioxide, and based on UV-vis DRS absorption spectrum analysis, adding graphene can reduce the band gap of titanium dioxide from 3.08 eV to 2.42~2.83 eV. In the photocatalytic experiments, the degradation of methylene blue（MB）dye wastewater in the T4GOA photocatalyst composite can achieve 100% removal efficiency in just 30 minutes under ultraviolet light irradiation, effectively increasing by about 38% degradation efficiency when compared with those of unmodified titanium dioxide photocatalyst. The reaction rate constant is significantly increased from 4.506×10-2min-1to 1.693×10-1min-1. The degradation efficiency of dye wastewater in photocatalysts composite with graphene modifications is shown to be higher than that of titanium dioxide photocatalysts without modifications under visible light irradiation, with T4GOA composite having the highest photocatalytic efficiency. The results confirm the feasibility of using a titanium dioxide photocatalyst material modified with graphene to increase dye degradation efficiency.