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

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 (C_F) 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 C_F 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.