二氧化碳還原反應(Carbon dioxide reduction reaction CO2RR)，為將二氧化碳轉變為具有高經濟價值的產物之反應。由於全球二氧化碳在大氣中的濃度不斷攀升，是今日極端氣候的主要肇因，減少二氧化碳在大氣中的含量便成為現今高度重視的研究之一。2021年第76屆聯合國大會，全球128個國家已宣示2050年要達到淨零排碳目標，短期目標則是2030年需減少43%排碳。近期內企業透過製程優化、綠電使用、與資源循環等方法減少排碳，面對二氧化碳排放則有碳封存與碳捕捉等成熟的技術可以應用。但若要將二氧化碳真正減量，CO2RR是未來的關鍵技術，不僅是循環經濟的表現，同時也是化學能再利用的表現。然而直到今日，CO2RR材料的選擇與系統種類、參數研究方面仍有許多亟需改善之空間。
在本研究中，我們以離子交換薄膜燃料電池組作為電化學模組，並以連續式進料反應器測試CO¬2RR電化學行為。電池的兩極則為氣體擴散電極，陰陽兩極皆以噴塗的方式均勻塗佈觸媒材料在擴散電極基材上，並以陰離子交換薄膜作為區隔電池組中陰陽兩極之固態電解質。本研究專注於陰極觸媒之載體(support)與其界面對於CO2RR電化學反應之影響。本研究以銅金屬 (Copper, Cu)作為陰極觸媒，深入探討鹼土金屬氧化物固體鹼，也就是氧化鎂 (Magnesium oxide, MgO)，如何影響銅觸媒與CO2 的交互作用。利用濕式含浸法，我們成功的製備了晶相和大小均勻的氧化鎂負載金屬銅觸媒 (Cu@MgO)。此觸媒較碳黑附載或單純金屬銅有明顯 CO2RR 之活性提升並且同時抑制競爭的產氫反應。除了電化學轉化反應的測試，我們還利用擴散反射式紅外線轉換光譜儀 (DRIFT) 搭配質譜儀作程序升溫之CO2 吸附光譜 (IR) 和脫附分析 (TPD) 來探究活性提升之根本原因並且提供可能的解釋。我們的結果顯示，Cu@MgO有不同於純MgO和純Cu的CO2 吸附構型，並且有更多的CO2吸附於Cu上，促進CO2RR。

The carbon dioxide reduction reaction (CO2RR) has become a key area of research nowadays because of its potential for utilizing renewable energy sources to transform waste CO2 into value added products and create incentives for CO2 capture. At the 76th United Nations General Assembly, 128 countries have announced to achieve carbon neutrality by 2050 and 43% reduction in 2030. Although carbon sequestration and carbon capture can be applied, CO2RR is one of the key technologies to make it economically justified. However, for CO2RR, there is still plenty room for improvement as the energy efficiency to electrochemically reduce CO2 is not yet satisfactory.
In this study, we utilized the membrane electrode assemblies (MEA) to carry out CO2RR continuously with the anode fed with pure water and cathode with humidified CO2. The MEA consists of an anion exchange polymer membrane sandwiched between the cathode gas diffusion electrode and the anode porous transport electrode. Our research focuses on the catalyst support materials and how they influence the electrochemical performance of the cathode catalyst. Specifically, we are studying the impact of solid base materials, magnesium oxide (MgO) in our case, on the copper (Cu) catalyst. Our results show that the MgO supported Cu catalyst (Cu@MgO) had compelling CO2RR reactivity and selectivity against hydrogen evolution when compared with carbon supported or self-supported Cu. Temperature resolved CO2 adsorption infrared spectroscopy and desorption profiles reveals the enhanced binding of CO2, both in strength and quantity, on Cu@MgO that is different from pure MgO and Cu. The enhanced CO2 binding on Cu is therefore considered as the origin of the much higher CO2RR activity demonstrated by Cu@MgO.

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