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 H2SO4, KOH and Na2SO4 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 Na2SO4 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 Na2SO4 for developing high energy density and environment friendly systems.