Fluorescent brightener CBS-X doped polypyrrole as smart electrode material for supercapacitors

• Fluorescent brightener CBS-X was used as dopant of polypyrrole for the first time.
• PPy/CBS-X S-2 exhibited the highest electrical conductivity and the largest specific area.
• It possessed high electrochemical specific capacitance and electrochemical stability.
• Its electrochemical activity could be easily monitored by photoluminescence.

Fluorescent polypyrrole nanospheres (PPy/CBS-X) with uniform diameter were synthesized via a chemical oxidation polymerization with fluorescent brightener, 2,2′-([1,1′-biphenyl]-4,4′-diyldi-2,1-ethenediyl)bis-benzenesulfonic acid disodium salt (CBS-X), as dopant. The sample S-2 containing 1 mol% CBS-X simultaneously exhibited the highest electrical conductivity of 31.3 S/cm and the largest specific area of 98.33 m2/g. When being used as electrode material for supercapacitors, it also possessed the high electrochemical specific capacitance (245.8 F/g) at a scan rate of 5 mV/s and the better rate capability and improved electrochemical stability than neutral (undoped) PPy, essentially attributed to a synergistic effect on the high doping level, large specific area and good π–π interactions from both PPy chains and CBS-X dopant. Most interestingly, the electrochemical activity of the fluorescent PPy/CBS-X could be easily monitored by photoluminescence. These features make the fluorescent polypyrrole nanospheres potential smart electrode material for high performance supercapacitors.

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