Study on CoMn-MOF@VO2/Graphene Aerogel for Supercapacitors

Abstract

Supercapacitors with a higher power density than batteries, a higher energy density than capacitors, and a longer cyclic life are promising energy-storage devices. Metal organic frameworks (MOFs) have large specific areas and are potential candidates for the electrode of supercapacitors. This study adopts the hydrothermal method to prepare CoMn-MOF@VO2/graphene aerogel as the supercapacitor’s electrode. Electrochemical properties of the electrode, hydrothermal temperature, and sulfurization effect were investigated. SEM micrograms show that CoMn-MOF crystals have a grain size of 3~7 m and cross-sectional surface of aerogel have a laminate structure and many pores. The increase of hydrothermal temperature from 120 oC to 160 oC decreases the highest specific capacitance from 510.9 F/g to 168.4 F/g, because of non-uniform distribution of large CoMn-MOF crystals causing a higher resistance. Electrodes with sulfurization exhibit an increase in capacitance to 792.5 F/g, due to a higher electric conductivity. Moreover, the sulfurized electrode experiences a smaller decrease in capacitance with increasing current density.

• Supercapacitors
• Metal organic frameworks
• Graphene aerogel
• Sulfurized electrode
• Capacitance

摘要

超級電容器(supercapacitors)具有高於電池的功率密度、高於傳統電容器的能量密度以及良好的充放電循環壽命等優點，是目前具潛力的儲能元件。金屬有機框架(metal organic frameworks, MOFs)材料具有高比表面積，可作為電化學儲能元件的電極。本研究使用二氧化釩/石墨烯氣凝膠當作基材，利用水熱法製備鈷錳-金屬有機架構@二氧化釩/石墨烯氣凝膠(CoMn-MOF@VO2/graphene aerogel)作為超級電容器之電極，量測其電化學性質，並探討MOF水熱溫度與電極硫化的效應。從SEM微結構分析，可看出CoMn-MOF結晶的顆粒大小約為3~7 m，氣凝膠的切面具有層狀結構及明顯的孔洞。當水熱溫度從120 oC上升至160 oC，會導致CoMn-MOF的顆粒較大且在氣凝膠中分布不均勻，造成電極阻抗增加，比電容值下降，量測得到的電極最大比電容值分別為510.9 F/g與168.4 F/g。硫化後的電極導電性較佳，阻抗較小，進而使電極的比電容值增加，其最大比電容值可提高至792.5 F/g，而且硫化後電極的比電容值隨電流密度增加而下降的幅度較小，代表電極在硫化後趨於穩定。

• 超級電容器
• 金屬有機框架
• 石墨烯氣凝膠
• 電極硫化
• 電容值

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