This study synthesized ultra-fine nanometer-scaled ruthenium oxide (RuO2) quantum dots (QDs) on reduced graphene oxide (rGO) surface by a facile and rapid microwave-assisted hydrothermal approach. Benefiting from the synergistic effect of RuO2 and rGO, RuO2/rGO nanocomposite electrodes showed ultra-high capacitive performance. The impact of different RuO2 loadings in RuO2/rGO nanocomposite on their electrochemical performance was investigated by various characterizations. The composite RG-2 with 38 wt.% RuO2 loadings exhibited a specific capacitance of 1120 F g−1 at 1 A g−1. In addition, it has an excellent capacity retention rate of 84 % from 1A g-1 to 10 A g−1, and excellent cycling stability of 89% retention after 10,000 cycles, indicating fast ion-involved redox reactions on the nanocomposite surfaces. These results illustrate that RuO2/rGO composites prepared by this facile process can be an ideal candidate electrode for high-performance supercapacitors.
High-performance and eco-friendly carbon electrode material for supercapacitors is still a challenge for both academia and industry. In this work, polyimide waste (PI)-derived, hierarchically porous, and nitrogen-rich carbon materials were prepared by simple hydrothermal treatment and carbonization using potassium hydroxide (KOH) as an activator. The effects of KOH/ preoxidized PI mass ratio and hydrothermal treatment time on the morphology, chemical and crystalline structure, and electrochemical performance were systematically investigated. Interestingly, it is noticed that hydrothermal treatment with KOH solution can promote the infiltration and destruction of preoxidized PI, thereby enhancing the activation effect and forming a hierarchically porous structure. The specific surface area (SSA) of porous carbon with hydrothermal treatment (e.g., PIC 2 -24h) was as high as 2593 m 2 g −1 , which is much larger than that of porous carbon without hydrothermal treatment (PIC 2 ). The as-prepared PIC 2 -24h presented a high specific capacitance of 229 F g −1 at 1 A g −1 , superb rate performance (205 F g −1 at 10 A g −1 ), and excellent cycle stability (94% capacity retention after 20,000 cycles at 1 A g −1 ), revealing that these PI-derived porous carbon materials can not only alleviate the environmental stress caused by the disposal of PI waste but also provide an ideal candidate electrode for high-performance supercapacitor applications.
As a typical binary transition metal oxide, ZnFe2O4 has attracted considerable attention for supercapacitor electrodes due to its high theoretical specific capacitance. However, the reported synthesis processes of ZnFe2O4 are complicated and ZnFe2O4 nanoparticles are easily agglomerated, leading to poor cycle life and unfavorable capacity. Herein, a facile microwave hydrothermal process was used to prepare ZnFe2O4/reduced graphene oxide (rGO) nanocomposites in this work. The influence of rGO content on the morphology, structure, and electrochemical performance of ZnFe2O4/rGO nanocomposites was systematically investigated. Due to the uniform distribution of ZnFe2O4 nanoparticles on the rGO surface and the high specific surface area and rich pore structures, the as-prepared ZnFe2O4/rGO electrode with 44.3 wt.% rGO content exhibits a high specific capacitance of 628 F g−1 and long cycle life of 89% retention over 2500 cycles at 1 A g−1. This work provides a new process for synthesizing binary transition metal oxide and developing a new strategy for realizing high-performance composites for supercapacitor electrodes.
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