| 摘要: | 在光電化學 (Photoelectrochemical, PEC) 當中光陽極產氧並不符合動力學的趨勢，因此利用生質 (Biomass) 的選擇性氧化加以取代，透過反應得到具高附加價值的生質化學品，希望能代替原本的石化產品。本實驗選用地表含量豐富、光電表現穩定且無毒的α-Fe2O3作為光陽極，適合使用於長時間的氧化反應。透過水熱法製備α-Fe2O3薄膜，其中摻雜鍺 (Ge) 可以增加電子濃度，讓α-Fe2O3的導電度與載子遷移率增加，在光電化學上有更好的表現。反應物方面選用木質素衍生物5-羥甲基糠醛 (5- Hydroxymethylfurfural, HMF)，透過氧化生成的2,5-呋喃二甲酸 (2,5-Furandicarboxylic acid, FDCA) 可聚合成聚2,5-呋喃二甲酸乙二酯 (Polyethylene 2,5-furandicarboxylate, PEF) 樹脂，可望能取代目前常用的聚對苯二甲酸乙二酯 (Polyethylene terephthalate, PET)。
透過裝載共觸媒幫忙捕捉電洞，降低再結合的機率，可以進一步幫助光電化學與氧化表現，透過改變電沉積時間與前驅液濃度裝載Nickel Phosphate (Ni-P)，再利用四甲基哌啶氧化物 (2,2,6,6-Tetramethylpiperidine-1-oxyl, TEMPO) 輔助催化，促使HMF轉化為FDCA。結果顯示在選擇性氧化表現上以電沉積30分鐘，前驅液中鎳與磷酸根莫爾比為15比200時有最佳表現，與未裝載的情況相比，在反應12小時後FDCA的選擇率從35.4 % 提升至67.1 %，產率也從11.8 %上升至35.7 %，HMF的轉化率也有61.1 %，不僅如此，光電流也從0.51 mA上升至0.79 mA。綜上所述，作為HMF選擇性氧化的光陽極，α-Fe2O3是十分具潛力的選擇，Ni-P作為共觸媒能有效的幫助FDCA的生成，在反應中佔有重要的角色。
;Anode oxygen evolution reaction ( OER ) is not kinetically favorable in photoelectrochemical ( PEC ) cell. Thus, it is feasible to replace OER by oxidizing the biomass into high value-added chemicals. In this work, we use α-Fe2O3 as the photoanode which is non-toxic, stable in PEC system and earth-abundant. First, Ge-doped α-Fe2O3 thin film was synthesized using hydrothermal method with germanium oxide (GeO2) adding into iron oxide precursor. Ge doping can increase electron concentration, conductivity and carrier mobility of α-Fe2O3. Therefore, it can improve the performance in PEC system. 5-Hydroxymethylfurfural (HMF) was used as the reactant and it was oxidized to 2,5-Furandicarboxylic acid (FDCA) which can be polymerized into Polyethylene 2,5-furandicarboxylate (PEF).
By loading the co-catalyst to capture holes and reduce the recombination, it can further enhance the photoelectrochemical and oxidation performance. Load Nickel Phosphate (Ni-P) by changing the electrodeposition time and the concentration of the precursor, and add 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) as a mediator which can facilitate the selective oxidation of HMF. The results show that for selective oxidation, the electrodeposition for 30 minutes and the molar ratio of nickel to phosphate in the precursor are the best at 15:200. Compared with the unloaded case, the selectivity of FDCA increased from 35.4 % to 67.1 % after 12 hours of reaction. The yield also increased from 11.8 % to 41.0 %, and the conversion of HMF also achieved 61.1 %. Moreover, the photocurrent increased from 0.51 mA to 0.79 mA. In conclusion, α-Fe2O3 is a promising chemical as a photoanode for the selective oxidation of HMF, and Ni-P, as a co-catalyst, can effectively help the formation of FDCA and plays a big part in the reaction. |
