人為排放二氧化碳導致溫室效應、全球暖化與海水酸化，因此如何減少環境中的二氧化碳並將二氧化碳轉換成有用的化學品，一直以來吸引了許多研究人員的關注。二氧化錳具有成本低、環保及高催化活性等優點，目前已廣泛被應用作為電化學還原反應中的電觸媒。本研究目的是自行合成MnO2電極且利用此電極當作陰極進行電還原化學反應將二氧化碳還原成有用化學品同時合成奈米碳管生長之碳纖維（CNTs/CF）作為陽極並氧化酚。首先使用水熱法製備α-MnO2、β-MnO2與γ-MnO2觸媒，再利用浸泡法將觸媒批覆於（CNTs/CF）以獲得α-MnO2/CNTs/ CF、β-MnO2/CNTs/ CF與γ-MnO2/CNTs/ CF，或以旋轉塗佈法將觸媒負載於ITO導電玻璃上以合成α-MnO2/ITO、β-MnO2/ITO與γ-MnO2/ITO，其中CNTs/ CF之合成乃透過化學氣相沉積儀使奈米碳管（CNTs）直接生長於碳纖維（CF）上；披覆後之電極皆在603K的溫度下煅燒30分鐘，以獲得最後製備之電極。所獲得之材料以TEM(穿透式電子顯微鏡)、SEM(掃描電子顯微鏡)、XRD(X-射線繞射分析)、CV(循環伏安法)和LSV(線性掃瞄伏安法)測定本研究中獲得材料的物化特性。此外並將所獲得的電極在0.1 M KHCO3的飽和的二氧化碳下進行二氧化碳之電化學還原反應並分析電還原反應之產物與陽極之酚氧化，研究結果顯示以MnO2作為電觸媒所製備的電極所進行的電化學還原二氧化碳反應之主要產物為CO、H2、C2H2O4、CH2O2，顯見本研究所開發的觸媒已有效的將二氧化碳轉變成有用的化學品並同時氧化酚。與其他研究結果相較，本研究α-MnO2/CNTs/ CF之氫產率優，證實本研究所發展之電極具有應用潛力且陽極可將酚降解60-70 %。並選擇還原效果較好的電極α-MnO2/CNTs/ CF比較不同電解液對二氧化碳還原之效果，發現0.1 M KHCO3針對氫氣還原為0. 01 M KHCO3 1.5倍。比較α-MnO2/CNTs/ CF在單槽或雙槽之氧化還原效果，發現雙槽中間具有薄膜可使氫離子傳遞至陰極增強還原效果。 Anthropogenic emission of carbon dioxide lead to greenhouse effect, global warming and ocean acidification. Therefore, how to reduce the emission of CO2 and convert CO2 into more reduced chemical species have been holding special attractions for researchers. MnO2 possesses advantages of low cost, environmental friendliness and high catalytic activity toward electrochemical reduction so as to be widely used as electrocatalysts in the process. The objectives of this study were to synthesize effective electrodes base on MnO2 catalysts and then be used to electrochemically reduce CO2 into useful products and synthesize CNTs/CF used to anode and oxidize phenol. Firstly, α-MnO2, β-MnO2 and γ-MnO2 was prepared via hydrothermal method. Then, the conductive glass of ITO (indium tin oxide) and CNTs (carbon nanotubes) grown carbon fiber (CNTs/CF) were used to load alpha-MnO2 via spinning coating so as to synthesize the electrodes of α-MnO2/ITO,β-MnO2/ITO and γ-MnO2/ITO and used CVD to obtain CNTs/CF, then synthesized to α-MnO2/CNTs/CF β-MnO2/CNTs/CF and γ-MnO2/CNTs/CF. The final electrode products were obtained via calcination under 603K for 30 mins after spinning coating of MnO2. The physicochemical properties of obtained materials in this study were determined by TEM, SEM, XRD, CV and LSV. The electrochemical activity of obtained electrodes was conducted in saturated CO2 solution with the electrolyte of 0.1 M KHCO3. The main reduced compounds generated during the electrochemical reduction of CO2 and oxidation of phenol. The result show MnO2 electrode reduced of CO2 that main product of CO, H2, CH2O2, C2H2O4. It is obvious that the catalyst developed in this study has been effective to convert carbon dioxide into useful Chemicals and oxidation of phenol at the same time. Compared with other studies, the hydrogen yield of α-MnO2/CNTs /CF is proved to be that the electrode developed by this study has the potential of application and the anode can degrade phenol by 60-70%. Choosing the best reduction efficiency compared α-MnO2/CNTs /CF in different from KHCO3 concentration. It was found 0.1 M KHCO3 1.5 times reduced to hydrogen of 0.01 M KHCO3. Compare single or double chamber which is better redox reaction ,it was found that the film in the middle of the double chamber allowed the hydrogen ions to be transferred to cathode side to enhance the reduction effect.
