製備具消毒效能之過氧化氫產生電極及操作優化

Abstract

過氧化氫為強氧化劑亦屬於活性氧物質，可攻擊細胞之大分子物質如脂質、蛋白質及核酸，抑制細菌及病毒等微生物生長，且反應後的過氧化氫分解成水，為環境友善無危害之消毒劑。近年來廣泛以電化學合成過氧化氫，其中氣體擴散電極可有效利用氧氣以提高過氧化氫之合成效率，此方法相較於傳統蒽醌法，其合成步驟簡單且快速，但目前針對電極之化學組成及模組操作參數上之研究有限，使得氣體擴散電極於過氧化氫合成上更具有探討性。 本研究以製備具疏水及透氣性之電極作為電合成過氧化氫之工具為主軸，並評估其於殺菌上的應用。以混合不同碳黑(XC及ppy)與CS介孔性碳材，製成碳黑介孔碳氣體擴散電極 (carbon black@meso-carbon gas diffusion electrode, CBMC-GDE)，探討不同化學組成之複合電極(XC72/CS與ppy/CS)對過氧化氫生成效能之影響，並藉由電化學分析優化模組操作參數(電流密度、電壓大小及電解液型態等)，探討不同氧氣供應方式(陽極產氧、電解液之溶氧及自陰極擴散之氧)之過氧化氫合成效率，與過氧化氫生成時之限制反應物。 研究結果顯示，於定電壓模式，XC/CS複合電極具較好之過氧化氫產生效率；而於固定電流模式，ppy/CS相較XC/CS複合電極可產生較高之過氧化氫。模組操作參數之結果顯示，當陰極電壓控制在0.2 V時，電流效率可達83%；此外，當供應之電流密度小於20 mA/cm2時，有較好之電流效率；試驗中亦發現相較於使用Na2SO4, NaNO3及NaCl為電解液，於NaClO4為水溶液時可有效避免過氧化氫合成時之副反應產生，提高過氧化氫之生成效率。模組中之氧氣供應方式對過氧化氫生成速率影響為自陰極擴散優於僅靠電解液中之溶氧，而單純使用陽極產氧則最低，故此模組相較傳統電化學合成法可提高過氧化氫生成效能；綜觀上述，本研究所製備之CBMC-GDE具疏水及透氣性，可有效利用氧氣大幅提高過氧化氫之生成效能，且應用於消毒抗菌試驗上可達快速、簡單及有效之殺菌效果。

Hydrogen peroxide (H2O2) is a strong oxidant which is also known as a reactive oxygen species (ROS) and could be acted against bacteria and viruses by reacting with the thiol groups in lipids, proteins and nucleic acids. Moreover, H2O2 is an environmental compatibility and nonhazardous disinfectants because of its ultimate decomposition into water and oxygen. Recently, gas diffusion electrode (GDE), which is a gas-permeable material that can utilize oxygen efficiently, has been widely applied for H2O2 electrochemical generation. In addition, the synthesis step of GDE is demonstrated to be simpler and more rapid than that of the traditional anthraquinone oxidation (AO). However, little information is available in the field of electrode fabrication and operating optimization. In this study, fabrication of the gas diffusion electrodes with gas-permeable and hydrophobic properties for H2O2 generation was carried out to evaluate its application for disinfection. The various carbon black, such as XC72 and ppy, was assemble with CS of meso-carbon to fabricate carbon black@meso-carbon gas diffusion electrode (CBMC-GDE). The efficiency of H2O2 generation with various chemical compositions of XC/CS and ppy/CS composite electrodes were investigated. Applied current densities, cathode voltages and electrolytes were optimized via electrochemical analysis for H2O2 generation. In addition, to investigate the H2O2 generation of restricted reactants and the H2O2 generated efficiency of various oxygen supplies including anodic generation, dissolved oxygen of electrolyte and diffusion from cathode. The results show that XC/CS composite electrode generated a higher amount of H2O2 concentrations in the constant voltage mode, compared to ppy/CS composite electrode. In contrary, H2O2 generation by ppy/CS composite electrode was more pronounced in constant current mode, compared to XC/CS composite electrode. The results also show that the current efficiency was 83% when the applied voltage was 0.2 V at cathode. When the current density was less than 20 mA/cm2, current efficiency increased. We also found that the use of NaClO4 as electrolyte could effectively avoid the side reactions of H2O2 in contrast with Na2SO4, NaNO3 and NaCl. The effect of oxygen supplies for H2O2 generation rate in the following increasing order: anodic generation < dissolved oxygen of electrolyte < diffusion from cathode. In conclusion, the CBMC-GDE is a gas-permeable hydrophobic electrode which can utilize oxygen efficiently for H2O2 generation. Thus, the disinfection could be achieved quickly, simply and safely.