雙胞反應器進行光催化水分解結合二氧化碳還原

photocatalytic water splitting combine with CO2 reduction in twin reactor

李韋萱(Wei-Hsuen Lee)

指導教授 ： 吳紀聖

國立臺灣大學/工學院/化學工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.02113

摘要

全球暖化的嚴重性越趨受到關注，其造成了氣候劇烈的變遷及環境的影響，科學家嘗試了許多方法降低大氣層中溫室氣體的含量，其中以光觸媒還原二氧化碳成有機化合物，是一種無汙染且又可消除溫室氣體的產生替代能源方式。本研究的創新性在於利用雙胞反應器系統進行水分解反應結合二氧化碳還原反應，延續實驗室前人使用雙胞反應器及Nafion薄膜將產氧反應及還原反應系統隔開，避免了產物逆反應氧化的發生，還原端水分解半反應產氫作為二氧化碳光催化還原的氫源，期望達到增進二氧化碳還原成碳氫化合物的產率。利用WO3於左端半反應器進行水分解半反應產氧，及在右端半反應器使用一系列不同的還原觸媒進行水分解產氫及二氧化碳光催化還原的反應。還原觸媒包含InTaO4負載共觸媒ro-NiO, Cu; CuAlGaO4負載共觸媒Pt, Cu, Rh, ro-NiO。InTaO4用溶膠凝膠法製備，負載共觸媒ro-NiO,，Cu為使用初濕含浸法；CuAlGaO4採用固態熔融法製備，負載共觸媒Pt, Rh採用光沉積法。負載不同金屬具有不同還原效果，且對進行水還原產氫亦或進行二氧化碳還原具有選擇性。實驗以Fe3+/Fe2+為電子傳遞媒介於水溶液中，在pH值2.6下進行。以300W氙燈作為可見光源，使用以Fe3+前處理的Nafion 薄膜進行反應，在以Pt(1wt%)/CuAlGaO4做為還原觸媒的情況下可以得到最佳的還原效果，產生氫氣0.43μmol/g•h，甲醇1.80μmol/g•h，一氧化碳0.16μmol/g•h。在此條件下可得到(H2+3•CH3OH+CO):O2接近molar 2:1的比例，符合反應器兩端質量平衡。光量子效率估計約0.002%。產氫觸媒Pt(0.8wt%)/SrTiO3:Rh結合還原觸媒Pt(1wt%)/CuAlGaO4於還原端溶液，利用300W氙燈加濾片，AM1.5G的光源，可得(H2+3•CH3OH+CO):O2＝1.89，光量子效率0.0051%。AM1.5G的光源下，使用還原觸媒Pt(1wt%)/CuAlGaO4於還原端溶液，可得(H2+3•CH3OH+CO):O2＝1.95，光量子效率0.0035%。

關鍵字

光觸媒水分解 ； 二氧化碳光催化還原 ； 離子傳輸

並列摘要

Global warming becomes an serious problem nowadays. Greenhouse gas is one of the primary causes of global warming, such as CO2, N2O, etc. One of the promising solutions is to perform photoreduction of CO2 to produce fuel. CO2 can be reduced in water vapor or H2 by photocatalyst. Use H2 to reduce CO2 by photocatalyst under light irradiation is more possible based on thermodynamics. In this study, CO2 photoreduction is applied into a novel twin photoreactor, which can separate H2 and hydrocarbon from O2. We employed sol-gel derived InTaO4 and solid state method derived CuAlGaO4 loaded with different cocatalysts NiO, Cu, Pt and Rh to test its activity in the twin reactor. We used 300W xenon lamp as the visible light source and Fe3+ pre-treated Nafion membrane to separate two sides of half-reaction. We add commercial WO3 as oxygen catalyst into oxidation-side half reactor and adjusted pH value of both sides to 2.6. Pt/CuAlGaO4 showed activity for CO2 reduction to form methanol. The optimum amount of Pt cocatalyt is 1wt%. In this case, methanol, H2, and O2 produced with stoichiometric amounts. The yields of H2, methanol and CO were 0.43μmol/g•hr, 1.80μmol/g•h, 0.16μmol/g•h. Under this condition we can get (H2+3•CH3OH+CO):O2 molar ratio close to 2:1. The quantum efficiency is around 0.002%. Evolusion of product in a stoichiometric ratio indicated that water was consumed as a reducing reagent for the CO2 reduction. Combined Pt/SrTiO3:Rh and Pt/CuAlGaO4 together in reduction side under AM1.5G Xe lamp, (H2+3•CH3OH+CO):O2 molar ratio is 1.89, and quantum efficiency is 0.0051%. Use Pt/CuAlGaO4 under AM1.5G Xe lamp, (H2+3•CH3OH+CO):O2 molar ratio is 1.95, and quantum efficiency is 0.0035%.

並列關鍵字

CO2 photoreduction ； photocatalytic water splitting ； ion transportation

參考文獻

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