以蝦殼生物炭製備之氮摻雜階層式多孔活性碳電極於薄膜電容去離子技術脫鹽性能之研析

Abstract

薄膜電容去離子(Membrane Capacitive Deionization, MCDI)技術是一項具發展潛力的脫鹽技術，其電極材料在此扮演著十分重要的角色。生物炭 (biochar)為一種常見的碳材料，其在自然界中擁有豐富的資源、對環境友善以及具成本效益，因而被廣泛使用在MCDI電極材料中。氮摻雜技術與階層式多孔結構透過添加額外的電荷轉移位點、增加材料的比表面積以及良好的孔洞結構能夠有效提升生物炭的離子吸附容量。 本研究旨在透過in-situ的方法，在不同活化溫度下，製備氮摻雜階層式多孔蝦殼活性碳(SSHPC)。在同時進行氮摻雜與活化的過程中，蝦殼中原有的高氮含量作為氮的前驅物，而KOH則為活化劑。研究成果顯示以活化溫度800度製備之蝦殼活性碳(SSHPC800)擁有高比表面積(1786 m2/g)、高中孔比例(0.51)以及理想的氮形式比例(N-6: 31.7%, N-5: 30.7%, N-Q: 37.6%)。此外SSHPC800擁有出色的比電容值(111.85 F/g)、電源電壓降(0.04 V)以及電荷轉移阻抗(33.16 ΩΩ)，上述表現皆優於在其他活化溫度下製備的材料。SSHPC800在電容去離子(CDI)實驗中，相較於其他材料表現出優越的離子去除能力以及脫鹽效率，其平均脫鹽容量(MDC)與 充電效率分別為3.6 mg/g與13.6%。SSHPC800更被應用於薄膜電容去離子(Membrane Capacitive Deionization, MCDI)系統中，其MDC與充電效率可分別達到10.8 mg/g與137.6 %，整體表現比傳統CDI來得更佳。最後，SSHPC800在MCDI系統中進行連續性實驗測試也展現了絕佳的穩定性。SSHPC800於本研究中，成功地展現氮摻雜技術與階層式孔洞結構改質生物炭的潛力，並可應用在 MCDI系統中，成為一項有效且永續的脫鹽技術。

Electrode materials play a crucial role in Membrane Capacitive Deionization (MCDI), a promising desalination technique. As a prevalent carbon material, biochar-derivatives has been widely used in MCDI electrodes since it is abundant in nature, eco-friendly, and cost-effective. Modification with nitrogen doping and introducing hierarchically porous carbon structures are effective ways to enhance the adsorption capacity of raw biochar since it provides additional charge-transfer sites, increases specific surface area, and creates well-defined pore structure. In this research, N-doped hierarchically porous carbon derived from shrimp shell-biochar (SSHPC) was obtained via an in-situ synthesis process under various activation temperatures. During simultaneous doping nitrogen and activation, high nitrogen content in shrimp shell biochar was used as a nitrogen precursor and KOH was employed as the activator. Notably, SSHPC800, activated at 800 C, emerged as the highlight of this study. SSHPC800 presented an outstanding specific surface area (1786 m2/g), mesoporosity (0.51), and an ideal nitrogen composition (N-6: 31.7%, N-5: 30.7%, N-Q: 37.6%). Furthermore, SSHPC800 demonstrated excellent specific capacitance (111.85 F/g), iR drop (0.04 V), and Rct (33.16ΩΩ), which surpassed all other materials. SSHPC800 showcased its superior ion removal capacity and desalination efficiency with a MDC of 3.8 mg/g and a charge efficiency of 16.7% in CDI whereas exhibited a much better overall performance with better MDC (10.8 mg/g) and charge efficiency (137.6%) in MCDI. SSHPC800 has also proved its stability in consecutive electrosorption/desorption process in MCDI. In this study, SSHPC800 has successfully exemplified the potential of N-doped hierarchically porous shrimp shell-biochar in MCDI systems in the quest for efficient and sustainable water desalination technologies.