空氣中二氧化碳轉換成有價物質，可以降低大氣中二氧化碳濃度、解決全球暖化問題，同時達到化石燃料的循環利用，因此本研究將開發一薄膜反應器應用於將空氣中的二氧化碳轉化為有價物質，研究重點為結合二氧化碳氣體分離層及光觸媒反應層製成一光觸媒複合薄膜反應器，應用於捕捉空氣中的二氧化碳同時將其做光催化還原反應，還原成含有CH4之氣體，達成碳循環之目的。

光催化複合薄膜選用對CO2選擇性佳的Polyimide(PI)，CO2氣體分離層為摻有不同含量胺官能化GO(PEI-GO)的緻密結構，氣體反應層為摻有奈米TiO2(P25)光觸媒的多孔性雙連續結構。在氣體分離層加入0.1 wt% PEI-GO 後，可提供最適量CO2濃度給氣體反應層，透過端生成8.88 ppm 的CH4，於此條件的光觸媒複合薄膜氣體反應層中再摻入1.0 wt% graphene後，可有效抑制光誘導電子電洞對的再結合，進一步提升轉化效能生成11.1 ppm的CH4。

本研究以FTIR和ESCA確認PEI成功接枝在GO表面。由SEM、TMA和XRD結果可知，PEI-GO 比未改質GO可更均勻分散在PI基質中;XRD、PLAS和GPA結果可知，GO表面接枝PEI後所形成的位阻效應，會產生較多且大的自由體積，在 PI 基質中形成氣體較易通過的通道而提升氣體透過係數。SEM結果可確認反應層內部為多孔性雙連續結構;UV-Vis 結果可得知P25與graphene混摻後對薄膜之光吸收特性無顯著影響;PL結果證實加入graphene後可抑制光誘導電子電洞對再結合。

The conversion of carbon dioxide in the air into valuable substances can reduce the concentration of carbon dioxide in the atmosphere, solve the problem of global warming, and achieve the recycling of fossil fuels. Therefore, this research will develop a membrane reactor to convert carbon dioxide in the air into valuable substances. The focus of this work is to combine the carbon dioxide separation layer and the photocatalyst reaction layer to make a photocatalyst composite membrane, which is used to capture carbon dioxide in the air while doing a photocatalytic reduction reaction to reduce CO2 to CH4.

The CO2 separation layer is made of polyimide (PI) with good CO2 selectivity. The dense CO2 separation layer was doped with different contents of amine functionalized GO (PEI-GO). The photocatalyst reaction layer is PI doped with nano-TiO2 (P25) photocatalyst which was interconnected pore structure. After adding 0.1 wt% PEI-GO to the gas separation layer, the optimum CO2 concentration can be provided to the gas reaction layer, and 8.88 ppm of CH4 is generated at the permeation side. The photocatalyst composite membrane then mixed with 1.0 wt% graphene into photocatalyst reaction layer. After that, it can effectively inhibit the recombination of light-induced electron- hole pairs, and further improve the conversion efficiency to generate 11.1 ppm of CH4.

In this study, FTIR and ESCA confirmed that PEI was successfully grafted on the surface of GO. From the results of SEM, TMA and XRD, it can be seen that PEI-GO can be more uniformly dispersed in the PI matrix than unmodified GO. The results of XRD, PLAS and GPA show that the steric hindrance effect formed by the grafting of PEI on the surface of GO will produce larger interspacing between GO sheets. The gas can pass easily through larger interspacing and improves the gas permeability of gas separation layer. SEM results can confirm that the reaction layer has a porous bi-continuous structure. UV-Vis results show that the blending of P25 and graphene has no significant effect on the light absorption characteristics of the membrane. PL results confirm that the addition of graphene into reaction layer can inhibit the recombination of photo-induced electron and hole pairs.

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