臨場拉曼光譜技術應用於二氧化碳還原反應

Investigation of electrochemical CO2 reduction via in situ Raman system

廖梓伃(Tzu-Yu Liao)

指導教授 ： 陳浩銘

國立臺灣大學/理學院/化學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201702801

摘要

近幾年來，由於二氧化碳排放量的迅速增加，其還原反應受到許多科學家的重視，其中又以能產生碳氫化合物產物的銅金屬備受關注。然而，銅金屬的二氧化碳還原反應機制卻只有推測以及理論計算，並未被證明及詳細闡述。在這個研究中，臨場拉曼量測技術將運用於分析銅金屬表面上的二氧化碳還原反應機制。
拉曼光譜為良好鑑定鍵結的技術，與紅外光譜相比之下，並不會受到水的訊號干擾，十分適合進行臨場電化學量測。然而，當二氧化碳還原反應發生時，將會伴隨氣體產物的產生而干擾拉曼的訊號，為了解決這樣的問題，本實驗設計了一個可以配合拉曼直立式鏡頭及精密電極的反應槽。此拉曼裝置的巧思在於，為了避免產物氣泡的吸附而使用了長焦距鏡頭與水鏡交互搭配，另外還選用面積極小的電極來減少氣泡的生成。除了解決氣相產物對拉曼訊號的干擾外，提高拉曼散射訊號也是本研究的目標，因此本研究合成具有表面增強拉曼效應的銀金屬奈米立方為材料基板，在其表面上成功添加欲觀察的銅金屬薄層，藉此提高銅金屬與二氧化碳鍵結訊號的強度。最後藉由比對獲取的拉曼圖譜以及資料庫，可以鑑定出二氧化碳與催化劑表面反應產生的鍵結。除此之外，這些分析數據也吻合氣相層析–質譜法聯用量測的產物結果。
綜合上述實驗的資訊，本研究將能夠建立一個擁有臨場數據佐證的二氧化碳還原機制。

關鍵字

二氧化碳還原 ； 奈米材料 ； 臨場拉曼 ； 表面增強拉曼散射光譜

並列摘要

In recent years, CO2 reduction has been a growing priority for scientists due to the high level of emission. In this field, copper metal catalysts attract much attention because of the hydrocarbon products. However, the mechanism of CO2 reduction using copper metal has not been well-verified. In this work, in situ Raman spectroscopy measurement is applied to study the mechanism of CO2 reduction on copper.
Raman spectroscopy is widely used to identify the bonding states and also less influenced by water molecules than infrared spectroscopy. Thus, it is an effective technique to measure the spectrum of the reactions that happen in a solution. However, when CO2 reduction occurs, gases which interfere with the Raman signals are released as products. Therefore, we designed a new Raman cell coordinated with upright lenses and exquisite electrodes in order to solve this problem. In particular, lense with long focal length was chosen to prevent bubbles from attaching. Three in one electrodes with small surface area were also used to reduce bubble yield. In addition, we also aim to enhance the signal of Raman scattering. Therefore, we synthesized and used the SERS material, silver cubes, as the base of our catalysts, and add the sample copper that we want to investigate on it in order to enhance the signals from the intermediate states of CO2 reduction on copper. Finally, by comparing the obtained Raman spectrum with available data base, we can identify the intermediate bonding state of the CO2 reduction. Furthermore, these analyses can be used to predict the results of gas chromatography–mass spectrometry.
In conclusion, a well‐defined mechanism of CO2 reduction can be established by combining all the informations obtained from the experiments.

並列關鍵字

CO2 reduction ； nanomaterial ； in situ Raman ； SERS

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