生物燃料電池石墨氈陽極材料改質與特性分析

Abstract

生物燃料電池是利用微生物分解廢水中的有機物產生電力，目前的生物燃料電池受限於低功率密度與高成本，為了改善此問題，本研究使用石墨氈為陽極材料，針對石墨氈基材進行表面改質，並探討石墨氈在生物燃料電池中的電性表現。本研究以陽極材料作為研究對象，使用稻田底泥的厭氧產電菌作為母菌，石墨氈做為陽極材料，以無膜式空氣陰極裝置操作生物燃料電池。石墨氈分別以硝酸與硫酸進行表面改質，並嘗試加熱改變石墨氈的表面官能基，藉此改善石墨氈的親水性與生物親和性，並觀察陽極材料表面改質對於生物燃料電池的電性表現影響。以水滴定實驗測得石墨氈經過泡硝酸並加熱130℃後的親水性改善最佳，在循環伏安法中觀察到活化面積比未經表面改質的石墨氈增加超過30倍。生物燃料電池操作中，泡硝酸並加熱的石墨氈達到2253 mW/m2的功率密度，比未改質的石墨氈高出111%(1070 mW/m2)，電池的內阻也降低了45%。不論有無經過表面改質，電池的庫倫效率都維持在50%以上，且在進行40天的電池操作，電池的電壓輸出也相當穩定。在增加了陰極面積與縮短電極距離後，降低了活化過電位，使得生物燃料電池的最高功率密度達到3413 mW/m2。在本研究中成功使用簡易且低成本的製程改善了石墨氈的親水性與生物親和性，並成功達到擁有高功率、高庫倫效率與高穩定性的生物燃料電池。

Microbial fuel cell (MFC) is a kind of fuel cells that convert chemical energy into electric energy. It inoculates exoelectrogenic bacteria attached to the anode as a catalyst and degrades organic matter by electrode reaction. Bacteria transfers electrons to the surface of anode, and electrons flow to the cathode through the external circuits. On the other hand, oxygen is reduced electrochemically at cathode and water is produced. The overall reaction involves organic matter and oxygen, chemical energy is converted into electric energy, in which water and carbon dioxide are produced. In this work, graphite felts serve as anode which provide high specific surface area for bacteria to attach. Graphite felts were employed to nitric acid treatment (AT-N) and combination of nitric acid and heat treatment (AT-NH) to improve hydrophilicity. Linear Sweep Voltammetry and cyclic voltammetry analyses indicated AT-NH graphite felts provided the best electrochemical performance in this work. Maximum power density of microbial fuel cell equipped with AT-NH graphite felts was 2253 mW/m2 which was 111% and 21% higher than unmodified graphite felts and AT-N graphite felts, respectively. The internal resistance of microbial fuel cell equipping with AT-NH was reduced dramatically and AT-NH graphite felts contributed less than 16.5% of the internal resistance. By reducing the electrode distance and increasing the cathode area, maximum power density of MFC was increased to 3413 mW/m2. This work demonstrates a simple way to fabricate hydrophilic graphite felts and improve power generation of MFC.