微球型碘氧化鉍光觸媒於光催化分解水反應之研究

鉍氧化合物應用於汙水處理、光催化反應、分解水反應的相關研究已被多次證實有良好的光催化效能，當中鉍氧化鹵素的能隙較小，又以碘氧化鉍具有最小的能隙(1.73 eV-1.92 eV)，能利用可見光進行光催化反應。本研究利用同位水相合成法在低溫下製備出由奈米層狀結構組成之花狀3D微球型BiOI，經由X光繞射分析儀(XRD)鑑定其結晶結構與BiOI(JCPDS 73-2062)相符；利用高解析穿透式電子顯微鏡(HRTEM)觀察其晶格；由場發掃描式電子顯微鏡(FESEM)觀察BiOI形貌，可觀察到奈米層狀結構成核為大小5-7微米之球型；利用UV-vis檢測其光學性質，並經換算畫出Tauc plot得BiOI之能隙大小為1.85 eV，為可見光光觸媒。　　為了探討不同助產氧試劑對產氧效能的影響，於光催化分解水產氧的過程中分別添加犧牲試劑AgNO3和電子中間介體NaIO3，觀察並找出最佳化的產氧條件。接著利用含浸法及光沉積法將共觸媒釕(Ru)負載於BiOI上，以提升其光催化分解水產氧之效能。從產氧結果得知利用光沉積法負載Ru能有效提升BiOI產氧效能，在負載量為1 wt%時具有最高總產氧量及產氧速率，產氧總量可高達13642.41 μmole (產氧條件：0.25 g光觸媒、250 mL反應溶液、總照光時間5 h)，但產氧總量及產氧速率並不會隨Ru負載量的增加而增加或變快，過多的Ru負載於BiOI表面反而降低其對於光的吸收能力，導致產氧能力下降。　　除了利用添加共觸媒Ru提升BiOI光催化性能外，我們還使用金屬有機框架(MOF)與BiOI進行複合，期望能利用孔洞材料高比表面積的特性，讓BiOI合成在MOF框架上以提高比表面積進而提升光催化效能，但從實驗結果發現複合後之材料並無產氧效能，利用紫外光-可見光分光光譜儀得知MOF對光吸收效果不佳，且複合後BiOI形貌、結構較為不完整，亦有可能是導致無法產氧之因素，說明與BiOI進行複合的孔洞材料本身之性質會影響光觸媒產氧效能。

關鍵字

碘氧化鉍；光催化；分解水；產氧

並列摘要

Bismuth oxides have been reported to be a promising photocatalyst applying to waste water treatment, photocatalysis reaction, water splitting. Among them, BiOX (X=Cl, Br, I) have relative smaller band gap, especially BiOI. In the present work, flower-like BiOI microspheres composed of nanolayered structure were synthesized by in-situ coprecipitation method under an ambient temperature. The as prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray spectra, and UV-vis diffuse reflectance spectroscopy. BiOI could serve as O2-evolved photocatalyst with a O2 evolution rate of approximately 7578.8 μmole/h with 0.25 g photocatalyst from water splitting with addition of NaIO3 as a mediator under simulated sunlight irradiation. In addition, the BiOI microspheres structure was remained unchanged after photocatalytic water splitting, indicating that BiOI can be a promising visible-light-active photocatalyst. Then we added ruthenium by impregnation method and photodeposited method to improve the photocatalytic water splitting O2 production performance, 1 wt% Ru BiOI have the best photocatalytic performance, the amounts of O2 production could reached up to 13642.41 μmole with 0.25 g BiOI, 250 mL DI water within 5 hours, further Ru content did not improved. Also, we composited metal organic frameworks with BiOI expecting higher specific surface area, turned out it can’t produce O2, according to the UV-vis spectra, we realized the absorption intensity of MOF was too low, so that the O2 evolution was too low to detect, indicating the characteristic of MOF could directly affected the photocatalytic performance.