在全球能源及氣候危機的威脅下，開發替代能源及尋求化石燃料替代品成為 重要的研究方向，而利用再生能源以電化學方式將二氧化碳轉換為較高價值的化 學原料為當今熱門的研究主題。在本論文中，我們以八乙基紫質 (H2OEP) (1) 為配 位基，經過硝基及胺基作為 meso 位置推拉電子基修飾，並分別合成鎳、鈷和銅三 種金屬離子錯合物作為催化劑，進行電催化二氧化碳還原活性研究。我們將八乙 基紫質金屬錯合物吸附於碳黑粒子上，其中八乙基紫質金屬錯合物與碳黑之重量 比值為 1，使分子催化劑固定於碳質載體形成異相催化劑，結合氣體擴散電極 (GDE)，並應用於流式電解槽 (Flow cell ) 中進行二氧化碳還原反應 (CO2RR)，實 驗結果得到在以 Ag/AgCl 為參考電極之 -1.8 V 工作電位下，CoOEP (1-Co) 對於二 氧化碳還原至 CO 的法拉第效率 FECO最高達到 98%，且電流密度 jCO也高達 100.7 mA/cm2 ，而以硝基修飾後之 Co-NO2-OEP (2-Co) 在相同電位及相同電池條件下的 FECO = 99% 及 jCO = 104.2 mA/cm2，結果表明將八乙基鈷紫質結合導電碳材應用於 流式電解槽 (Flow cell) 的策略能高效催化二氧化碳還原反應生成一氧化碳，並且 由固定電流電催化實驗中發現在相同還原電流值下 Co-NO2-OEP (2-Co) 所反映出 的還原電位較 CoOEP (1-Co) 低約 0.1 至 0.2 V，表示以硝基作為拉電子基修飾後的 八乙基鈷紫質能更有利於電子傳遞至催化劑中心進行 CO2RR，展現出較佳的催化 活性。 ;Under the threat of escalating carbon emission and severe weather events, developing alternative energy technology for producing carbon feedstocks to replace fossil fuels as a strategy of decarbonization has become important. The electrochemical CO2 reduction to high valuable chemicals by green electricity, which can simultaneously reduce atmospheric CO2 concentration and produce fossil fuel alternatives has been considered as a possible strategy to mitigate the greenhouse gas. In this work, a comparative study of meso-nitro and amino functionalized octaethylporphyrin metal complexes (M = Ni, Co, Cu) mixed with carbonaceous materials (carbon black, CB) as heterogeneous catalysts and fabricated on the surface of gas diffusion layer (GDL) as a working electrode of flow electrochemical cells was conducted for electrochemical CO2 reduction. The results show that CoOEP (1-Co) as the active catalyst exhibits a 98% Faradaic efficiency (FE) for the CO formation with a partial current density (jCO) of 100.7 mA/cm2 at -1.8 V vs. Ag/AgCl, while Co-NO2-OEP (2-Co) exhibits 99% Faradaic efficiency (FE) to CO with an extraordinary partial current density (jCO) of 104.2 mA/cm2 under the same potential. Our results demonstrate that the combination of octaethylporphyrin cobalt complexes mixed with conductive carbonaceous material as the cathodic catalysts for flow cells provides an effective strategy for CO2 reduction reactions (CO2RR) to CO, and the presence of the electron withdrawing NO2 groups on meso position of CoOEP (1-Co) enhances the interfacial electron delivery rate to catalyst and exhibits better catalytic activity.
