Enhancing Supercapacitor Performance Using Carbon Dots as Versatile Additives in Both Titanium Dioxide-Based Electrodes and Sodium Sulfate Electrolytes

In this work, carbon dots were synthesized from sodium polyacrylate and demonstrated as versatile, effective electrode/electrolyte additives for enhancing specific capacitance and cycling stability of supercapacitors. An addition of only 5 wt % carbon dots to the TiO2 electrode significantly improved the specific capacitance by 348%. Furthermore, the addition of carbon dots to the Na2SO4 electrolyte additionally enhanced the specific capacitance by 229%. This results in a total improvement of 797%, almost eightfold better than the pristine TiO2 electrode and the Na2SO4 electrolyte. The fabricated supercapacitor exhibited an areal-specific capacitance of 247 mF cm(-2), the highest to date among other TiO2-based supercapacitors using Na2SO4 electrolytes. Moreover, it showed extraordinary rate capability and 96% retention of specific capacitance after 5000 cycles. From electrochemical analysis and contact angle measurement, it was shown that the carbon dots improved the performance of the supercapacitor by synergistically lowering the series resistance and enhancing the diffusion-controlled process, surface wettability, and pathways for ion diffusion. Ionic mobility and hydrated ionic radius were also found to be the critical factors in supercapacitors. The carbon dots proved to be potent additives for both TiO2-based electrodes and Na2SO4 electrolytes. The supercapacitor developed here has potential for electronic applications that require energy storage devices that exhibit environmental friendliness, excellent stability, straightforward fabrication, and low cost.

Automated summary

This study demonstrates the use of carbon dots as versatile additives for enhancing the performance of supercapacitors. By adding carbon dots to both the TiO2 electrode and Na2SO4 electrolyte, the specific capacitance of the supercapacitor was significantly improved, leading to a total improvement of 797%. The carbon dots also improved the rate capability and retention of specific capacitance after cycles.