Ultrahigh-performance titanium dioxide-based supercapacitors using sodium polyacrylate-derived carbon dots as simultaneous and synergistic electrode/electrolyte additives

In this work, a novel, facile method for enhancing electrochemical performance of supercapacitors was developed using colloidal TiO2 nanoparticles and sodium polyacrylate-derived carbon dots (CDs). The pristine TiO2 electrode in KOH electrolyte yielded a good specific capacitance of 1,050 mF cm(-2) at a scan rate of 5 mV s(-1). An addition of 10% w/w CDs to the TiO2 electrode increased the specific capacitance by 158%. Moreover, adding the CDs to KOH electrolyte further boosted the specific capacitance by 133%. An areal specific capacitance of 2,200 mF cm(-2) was obtained, which is the highest among TiO2-based supercapacitors to date and also higher than those of a large number of other metal oxide-based supercapacitors. Furthermore, the CD-doped supercapacitor gave excellent rate capability and improved the cycling stability over 5,000 cycles with 91.43% capacitance retention. Intensive electrochemical analysis was performed to justify that a significant improvement in the electrochemical performance was attributed to an increase in the number of transferred electrons, diffusion of electroactive species, electroactive area, and pseudocapacitance via strong electronic coupling and favorable interfacial phenomena provided by the carboxylate-rich, electroactive CDs. With a combination of simplicity, low cost, and ultrahigh performance, the ability of CDs as simultaneous and synergistic electrode/electrolyte additives opens up a new opportunity for the fabrication of robust, low cost energy storage devices in, but not limited to, supercapacitors. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

A novel method utilizing colloidal TiO2 nanoparticles and sodium polyacrylate-derived carbon dots (CDs) was developed to enhance the electrochemical performance of supercapacitors. Addition of CDs to TiO2 electrode and KOH electrolyte significantly increased the specific capacitance, leading to a high areal specific capacitance of 2,200 mF cm(-2). The CD-doped supercapacitor showed excellent rate capability and cycling stability, attributed to the strong electronic coupling and favorable interfacial phenomena provided by the CD additives.