光催氫化CO/CO2水溶液成碳氫化合物

Abstract

隨著工業的蓬勃發展，使得人類對於化石燃料的需求與日漸增，卻也導致大氣中的二氧化碳排放量逐年遞增，造成環境產生了劇烈的變化，例如:溫室效應、全球海平面上升、海洋生態改變等等。這些因為工業上的發展與科技的進步而衍生出的環境衝擊問題，已經引起全球科學家的注意和尋找改善方法。其中利用光觸媒還原二氧化碳成有機化物，兼具了無汙染又可消除二氧化碳的優點為目前許多科學家嘗試的方法。 由於二氧化碳的還原反應效率較低，因此利用一氧化碳活性較高的特性，將一氧化碳與二氧化碳同時當作反應物進行還原反應，並延續實驗室前人的雙胞反應器且利用薄膜將反應器兩端的產氧端反應與還原端反應分開，以降低產物逆反應的發生機率，由於在還原端的水分解所產生的氫可當作還原反應的氫源，以期望達到提高還原反應的效率。 本實驗利用WO3於反應器氧化端進行水分解半反應產氧，以及利用Pt/ CuAlGaO4與Pt/ SrTiO3:Rh於反應器還原端進行水分解產氫以及CO/CO2光催化還原反應，SrTiO3:Rh、CuAlGaO4皆採用固態熔融法製備，負載共觸媒Pt則採用光沉積法。以300W氙燈作為可見光源，當反應物為純CO2時，得到氫氣平均產率0.12μmol/g•h，氧氣的平均產率為0.76 umole/g•h，而甲醇的平均產率為0.52 umole/g•h。當反應物CO:CO2為1:10時，氧氣的平均產率為1.5umole/g•h，氫氣的平均產率為0.1 umole/g•h，而甲醇的平均產率為1 umole/g•h。由此可知，當反應物為CO/CO2時，其甲醇的產量效率明顯增加很多。當反應物CO:CO2為1:5時，甲醇的量並不會較CO:CO2為1:10多，推論原因為，CO的溶解度有限，在CO:CO2為1:5與CO:CO2為1:10兩種狀況下，水溶液中的CO含量是差不多的，因此無法提升還原反應的效率。

With the rapid development of industry, the need of fossil fuels for humans increases.But this condition also leads to emissions of carbon dioxide in the atmosphere, resulting in a dramatic change in the environment, such as the greenhouse effect, global sea level risesetc. Because of these developments and technological advances in the industry, the environmental impact have attracted the attention of scientists around the world and looking for ways to improve .One of promising solutions is using photocatalysts to convert carbon dioxide to hydrocarbons. But the low efficiency of the carbon dioxidereduction reaction is a problem for scientists. Because ofthe better activity of carbon monoxide, using carbon monoxide and carbon dioxide to do the reduction experiment is a better way to improve the efficiency.In this study, CO2 photoreduction is applied into a novel twin photoreactor, which can separate H2 and hydrocarbon from O2. We employed WO3as oxygen photocatalyst,solid state method derived CuAlGaO4 loaded with Pt as reduction photocatalyst, and employed solid state method derived SrTiO3:Rhloaded with Pt as hydrogen photocatalyst.We used 300Wxenon lampas the visiblelight source and Fe3+ pre-treatedNafionmembrane to separate two sides of half-reaction. and adjusted pH value of both sides to 2.6. When the reactant was pure CO2, the average yield of hydrogen is 0.12μmol / g • h, the average yield of oxygen is 0.76 umole / g • h, and the average yield of methanol is 0.52 umole / g • h. When the reactant of CO/CO2 is 1:10, the average yield of oxygen is 1.5umole / g • h, the average hydrogen yield is 0.1 umole / g • h, while the average yield of methanol and 1 umole / g • h.From the study, when the reactant is CO/CO2, the efficiency of carbon dioxide reduction significantly increases a lot.But when the reactant of CO/CO2 is 1:5, the amount of methanol is not more than the methanol fromthe reactant of CO/CO2 is 1:10. We think the reason is the low solubility of CO. Because the amount of CO in the solution in the two conditions is similar, it could not increase the efficiency of carbon dioxide reduction.