在過去的一個世紀裡，大氣中的二氧化碳 (carbon dioxide, CO2) 排放量急劇增加。 CO2 還原反應 (CO2 reduction reaction, CO2RR) 是減少全球碳足跡最有希望的解決方案之一。具有高選擇性 (selectivity) 和活性的催化劑已在H型反應槽(H-cells)中得到廣泛研究。然而CO2RR在H-cells 的應用因其產量低，電流密度通常小於10 mA/cm2，限制其商業化應用。 因此，本研究將銅、氧化銦 (Cu-In2O3) 觸媒塗佈於H-cells和流通槽(flow cells)中的玻碳電極 (glassy carbon electrode, GCE)以及氣體擴散電極 (gas diffusion electrode, GDE)上，並研究其CO2 還原成一氧化碳 (carbon monoxide, CO) 的選擇性以及電流密度。在H-cells 的測試中， GCE 和 GDE 上的觸媒在 -0.7 V (vs. RHE) 下有著96和 92 % 的高CO法拉第效率 (faradaic efficiency, FE)，其電流密度分別為 3 和 6 mA/cm2。此外，在液體和氣體進料的flow cells中，CO FE 分別為 89和 86 %，具有 30 和 90 mA/cm2 的高電流密度，遠高於 H-cells 5 倍和 15 倍的電流密度。因H-cell的設計改善了質量傳輸 (mass transfer) 問題並降低了電極之間的電阻， 使其觸媒效能有著極大的提升，本研究提供了一種有效的方式，可將實驗室規模的 CO2RR 朝向工業應用發展。 ;The carbon dioxide (CO2) emission in the atmosphere has increased dramatically in the past century. The CO2 reduction reaction (CO2RR) is one of the most promising solutions to reduce the global carbon footprint. The catalysts which have high selectivity and activity have been widely studied in H-cells. However, the application of H-cells is still far from the commercialization of CO2RR because of its low productivity (< 10 mA/cm2). In this study, a comparative study of Cu-In2O3 catalysts immobilized onto glassy carbon electrode (GCE), gas diffusion electrode (GDE) in H-cells and flow cells is conducted to selectively reduce CO2 to carbon monoxide (CO). In the setup of H cells, catalysts on GCE and GDE exhibit a high CO faradaic efficiency (FE) of 96 and 92 % with a current density of 3 and 6 mA/cm2, respectively, at -0.7 V vs. RHE. Furthermore, in liquid and gas feed flow cells configurations, the CO FE is 89 and 86 % with an extraordinarily high current density of 30 and 90 mA/cm2, which increase by the factor of 5 and 15 compared with that in H-cells, respectively. These outstanding catalyst activities have been achieved through the flow cell design that overcomes the mass transfer issues and reduces the resistance between the electrodes. This study provides an effective strategy to move CO2RR in lab scale towards industrial application.
