Hydrogen production from photocatalytic water splitting via TiO2 and TiO2/CuO thin-film photocatalysts irradiated with visible light- Effects of sacrificial agents

[[abstract]]本研究旨在分別擷取n型與p型半導體氧化物優點，建構一複合n型二氧化鈦與p型銅氧化物之光電催化水裂解反應系統，期能在可見光為光源下，進行水裂解產氫的反應。本研究除應用單純的二氧化鈦半導體光觸媒外，亦製備TiO2/CuO複合薄膜光觸媒，藉以提升光催化水裂解產氫的效能。研究中藉由測試不同外加電壓、光源、以及醇類犧牲試劑等可能影響產氫速率反應參數，除了建立相關試片水裂解產氫反應的基本資料外，也藉此探討可見光水裂解產氫的反應機制。 本研究利用磁控濺鍍技術製備所需的二氧化鈦薄膜光觸媒，實驗所採用的光催化水裂解產氫反應系統，主要由兩個密閉的石英玻璃反應槽所組成，分別配置以光觸媒電極與白金絲相對電極，同時以飽和甘汞電極為參考電極，並質子交換膜連結。實驗時，以Na2CO3溶液為電解液，進行光生電流與氫氣速率的檢測。另外，啟動光觸媒的光源包括紫外線燈管(365nm)、LED藍光(470 nm)、以及模擬太陽光等，同時也針對模擬太陽光亦利用過濾片，分別篩選出波長為200~400 nm、440~460 nm、540~560 nm、600 nm以上等特定波長範圍的可見光，以確認所製備光觸媒在可見光下產氫的可能性。 研究結果顯示：所製備的TiO2/CuO薄膜光觸媒電極，其能隙約為1 7~2 0 eV，已紅移至可見光範圍，也可以產生更強的光生電流；單純TiO2與複合TiO2/CuO光觸媒，皆具有不錯的光電催化水裂解產氫的效果；針對單純TiO2光觸媒，在近紫外光下，且在分別以甲醇與乙醇為犧牲試劑時，可分別提昇至2 65倍與2 8的產氫速率；針對TiO2/CuO可見光薄膜光觸媒，在近紫外光下，且分別添加甲醇與乙醇為犧牲試劑時，可分別提昇至6 27倍與5 91倍的產氫速率。若在模擬太陽光，則可以分別增加至4 24倍與4 59倍的產氫速率。甲醇等犧牲試劑的添加，有助於延緩光觸媒電子與電洞再結合速率，促進產氫反應的發生；本研究所獲得的最快產氫速率，在紫外光與模擬太陽光下，分別可達到5 603×10-6 mole/cm2hr與5 696×10-6 mole/cm2hr，此時的光生電流強度分別是23 02×10-4 A與28 710×10-4 A；本研究驗證所製備的複合TiO2/CuO光觸媒電極，可在可見光下，順利地進行水裂解產氫反應。[[abstract]]This study aims the n-type and p respectively type semiconductor oxide advantage to construct a complex n-type titanium dioxide and p-type photoelectric copper oxide catalytic splitting reaction of the system for the next phase in the visible light energy water splitting hydrogen production reaction In this study in addition to the simple application of titanium dioxide semiconductor photocatalyst is also preparing TiO2 / CuO composite film photocatalyst In order to enhance the effectiveness of photocatalytic water splitting hydrogen production Study by testing different applied voltage light and sacrificial reagents such as alcohols may affect the rate of hydrogen production reaction parameters In addition to basic information on the establishment of relevant specimens water splitting reaction of hydrogen production but also to take investigate hydrogen production from water splitting visible reaction mechanism The TiO2 thin film probes were prepared by compositing TiO2 with copper oxides via magnetron sputtering processes Consists mainly of quartz glass reaction vessel is composed of two closed are disposed in the photocatalyst electrode and platinum wire counter electrode while a saturated calomel electrode as the reference electrode and a proton exchange membrane link Experiment to Na2CO3 solution as the electrolyte and the light-generated current rate of detection of hydrogen Further the light source comprises UV lamp (365nm) LED blue light (470 nm) and the simulated sunlight etc but also for the use of artificial sunlight filters are respectively filtering a wavelength of 200 ~ 400 nm 440 ~ 460 nm 540 ~ 560 nm over 600 nm and the above specific wavelength range of visible light prepared to confirm the possibility of visible light photocatalyst in hydrogen production The results showed that: TiO2 / CuO films prepared photocatalyst electrode its energy gap of about 1 7 ~ 2 0 eV has been moved to the visible red range can also produce a stronger photocurrent; Pure TiO2 and composite TiO2 / CuO photocatalyst all with good catalytic water splitting hydrogen production photoelectric effect; For pure TiO2 photocatalyst in the near ultraviolet light and when the methanol and ethanol for the sacrificial agent respectively and the hydrogen production rate can improve to 2 65 times and 2 8 times; For TiO2 / CuO visible light photocatalyst film in recent ultraviolet light and the methanol and ethanol were added at the expense of reagents hydrogen production rate can be increased to 6 27 times and 5 91 times respectively If the simulated sunlight you can increase the hydrogen production rate respectively to 4 24 times and 4 59 times Adding methanol and other sacrificial agent to help slow the photocatalyst electron and hole recombination rate promote the occurrence of hydrogen production reaction; Fastest hydrogen production rate obtained in this study under UV and simulated sunlight respectively can be achieved 5 603?10-6 mole/cm2hr and 5 696?10-6 mole/cm2hr Photocurrent intensity at this time were 23 02?10-4 A and 28 710?10-4 A; This study verified the composite TiO2 / CuO photocatalyst electrode can be in visible light smoothly water splitting hydrogen production reaction