Improving energy storage ability of Universitetet i Oslo-66 as active material of supercapacitor using carbonization and acid treatment

• Published in: Journal of energy storage 2021-05, Vol.37, p.102480, Article 102480
• Main Authors: Sung, Yu-Shun, Lin, Lu-Yin
• Format: Article
• Language: English
• Subjects: Acid treatment; Carbonization; Metal–organic framework; Supercapacitor; UIO-66
• ISSN: 2352-152X; 2352-1538
• DOI: 10.1016/j.est.2021.102480

•UIO-66 is made using precursors with pH of 1, 2, 4 and 6 in hydrothermal process.•Acetic acid acts as controlling and capping agents to prepare UIO-66 octahedron.•Carbonization process and acid treatment converts UIO-66 to carbon without metal.•Symmetric supercapacitor with CMOFAT4 electrode shows CF of 100.9 F/g at 30 mV/s.•Energy density 2.1 Wh/kg at 200 W/kg and CF retention 85% in 10,000 times cycling. The zirconium-based metal organic framework, Universitetet i Oslo-66 (UIO-66), has attracted much attention as electroactive material for supercapacitors. The carbonization and acid treatment are applied to enhance the energy storage ability of UIO-66. The detail physical and electrochemical comparison are firstly discussed in this work to understand the carbonization and acid treatment effects. The octahedron morphology is obtained for UIO-66 and the derivatives with carbonization and acid treatments. The largely reduced size and rougher surface are obtained for the UIO-66 with carbonization and acid treatments (C-UIO-66-AT) due to the escape of carbon gas and removal of ZrO2. A higher specific capacitance (CF) of 117.7 F/g is obtained for the C-UIO-66-AT electrode than those of 0.61 and 32.78 F/g for UIO-66 and C-UIO-66, respectively, owing to the carbon nature with higher porosity and rougher surface for the former case. The solid-state supercapacitor (SSC) composed of C-UIO-66-AT electrodes and gel electrolyte shows a potential window of 0.9 V and a maximum specific energy of 2.133 Wh/kg at the specific power of 200 W/kg. The CF retention of 85% and Coulombic efficiency of 100% are also achieved for the SSC after 10,000 times repeated charge/discharge cycling process. This work proposes a simple method to largely enhance the energy storage ability of UIO-66. More discussion of carbonization and acid treatment parameters will be proposed in near future.