High voltage supercapacitor built with seaweed carbons in neutral aqueous electrolyte

High oxygen content (10–15 at.%) nanotextured carbons were obtained by pyrolysis of seaweeds at 600–750 °C and applied as electrodes for supercapacitors in H 2SO 4, KOH and Na 2SO 4 aqueous media. Interestingly, the potential stability window measured in a three-electrode cell configuration depends both on the nature of the oxygenated surface functionality and on the electrolyte pH. A high value of 2.4 V was observed in Na 2SO 4 for the seaweeds pyrolysed at 600 °C, showing that the surface functionality strongly influences the over-potentials of di-hydrogen evolution and carbon oxidation. Symmetric capacitors built from the seaweed carbons exhibited an excellent cycle life for voltage values up to 1.6 V, showing the promise of Na 2SO 4 for developing high energy density and environment friendly systems.