To effectively improve the energy density and reduce the self-discharging rate of micro-supercapacitors, an advanced strategy is required. In this study, we developed a hydroquinone (HQ)-based polymer-gel electrolyte (HQ-gel) for micro-supercapacitors. The introduced HQ redox mediators (HQ-RMs) in the gel electrolyte composites underwent additional Faradaic redox reactions and synergistically increased the overall energy density of the micro-supercapacitors. Moreover, the HQ-RMs in the gel electrolyte weakened the self-discharging behavior by providing a strong binding attachment of charged ions on the porous graphitized carbon electrodes after the redox reactions. The micro-supercapacitors with HQ gel (HQ-MSCs) showed excellent energy storage performance, including a high energy volumetric capacitance of 255 mF cm−3 at a current of 1 µA, which is 2.7 times higher than the micro-supercapacitors based on bare-gel electrolyte composites without HQ-RMs (b-MSCs). The HQ-MSCs showed comparatively low self-discharging behavior with an open circuit potential drop of 37% compared to the b-MSCs with an open circuit potential drop of 60% after 2000 s. The assembled HQ-MSCs exhibited high mechanical flexibility over the applied external tensile and compressive strains. Additionally, the HQ-MSCs show the adequate circuit compatibility within series and parallel connections and the good cycling performance of capacitance retention of 95% after 3000 cycles.

This experiment was conducted to confirm the efficiency of introducing natural organic matter, crushed kenaf (Hibiscus cannabinus L.), which could lead to soil physicochemical improvement and crop growth improvement in reclaimed land. The plant height of economical crop kenaf after adding crushed kenaf per 3,000 kg 10a -1 as organic matter in 2020 was 219.5 cm. This was 7% less growth than the kenaf grown in standard fertilization, and 13.4% higher than the kenaf grown under in natural non-managed state without fertilization. The kenaf yield in the first year of organic matter treatment in non-developed reclaimed land was 3,215 kg 10a -1 which was 14.7% higher compared to that of under in natural non-managed state without fertilization and 83.9% yield of standard fertilization treatment. However, in the second year of cultivation, the growth and yield of treated with crushed kenaf as an organic matter were increased significantly. The main reason is that enough time was given for the decomposition of the input crushed kenaf, and the effect of kenaf cultivation as a crop on improving the soil environment was clearly appeared. So, the plant height in the second year of kenaf treated with crushed kenaf as an organic matter was 320.9 cm, which was 46.2% higher than that in the first year. In addition, yield also increased significantly, reaching 5,916 kg 10a -1 , an 84% higher compared to that of the first year. This rate of yield increase was larger than 15% of in natural non-managed state without fertilization or 33% of standard fertilization treatment, which showed that using kenaf as an organic matter was much more effective in improving the soil environment of reclaimed land and improving crop growth and yield.