以內照明蜂巢式反應器進行CO2光催化還原

Abstract

將二氧化碳與水在光照射之下，經由光觸媒催化為有價值的有機化合物，稱之為「人工光合作用」，有助於解決全球暖化與能源危機。本研究以溶凝膠法製備SiO2與NiO/InTaO4，將SiO2與NiO/InTaO4依序覆膜於蜂巢狀陶瓷載體上，形成多層結構，SiO2層有助於避免觸媒掉進載體孔洞中造成觸媒浪費，觸媒經過1100 oC鍛燒形成銦鉭晶相。蜂巢式反應器中，於載體的每一個通道內置入PMMA側面發光光纖，光可經由光線傳送並照射到觸媒表面，在光纖的側面鑿洞以增加側面發光強度，並於光纖尾端加金屬鍍膜以增加光反射，同時進行氣相光催化還原二氧化碳，以GC/FID層析儀分析主要產物為甲醇與乙醛。由UV-Vis圖譜得知銦鉭觸媒可吸收至可見光波段，能隙為2.7 eV，添加NiO共觸媒後能隙下降為2.2 eV，並經由XRD圖確認無雜相形成，SEM圖可見觸媒均勻附著於載體表面，並可觀察到NiO形成於InTaO4表面；利用光纖設計增加側面發光比率，比較不同光纖的甲醇產率，經過側面鑿洞與Pt尾端沉積的光纖，室溫下使用42.46 mW/cm2的可見光照射下，甲醇最佳產率為0.16 µmole/g•hr，當光源轉換為AM1.5 G模擬太陽光時，產物轉移為乙醛，以不同鎳含量與不同溫度下的活性比較，在反應溫度為70 oC時2.6%NiO/InTaO4獲得最佳產率為0.3 µmole/g•hr。

Global warming and fuel shortage are undeniable enviromental and energy problems nowadays. To solve these two problems, CO2 and water can be converted into organic compounds via photocatalysts under light irradiation, which is also called artificial photosynthesis. In the research, sol-gel prepared SiO2 and NiO/InTaO4 were coated sequentially on monolith to form multilayer structure. The catalyst was calcined to form crystal at 1100 oC. PMMA fibers with caves which can increase the side emission of light were put inside each channel of monolith. Furthermore, the end of the fibers was deposited a mirror to increase the light refletance from the end. The UV−VIS spectra of powder InTaO4 as well as NiO loaded InTaO4 indicated that both photocatalysts could absorb visible light. Pure InTaO4 was observed from XRD pattern. From SEM images, uniform catalyst layer and NiO were formed on monolith surface. The methanol yield achieved 0.16 µmol/g•h with visible light intensity of 42.46 mW/cm2 at 25°C. The product shifted to acetaldehyde under AM1.5G sunlight irradiation which yield obtained was 0.3 µmol/g•h at 70 °C on 2.6%NiO/InTaO4.