Oxygen and nitrogen-doped carbon particles derived from pyrolysis of Chlorella vulgaris and Spirulina platensis microalgae as an efficient electrode material for supercapacitor application

This study consists of the thermal activation of Chlorella vulgaris and Spirulina platensis microalgae with a potassium hydroxide (KOH) chemical agent in a carbon dioxide (CO2) atmosphere and the formation of nitrogen and oxygen-doped material from the hydrothermal interaction of the obtained activated carbons with nitric acid. The obtained nitrogen and oxygen-doped activated carbons were used in the production of electrochemical super capacitors. The morphological properties of the obtained pores were evaluated by transmission electron microscopy (TEM). Electrochemical properties were evaluated according to the cyclic voltammetry (CV) method in sulphuric acid (H2SO4), potassium chloride (KCl), and sodium hydroxide (NaOH) electrolytes with a scanning rate in the range of 2.5–50 mVs−1. Nitrogen and oxygen doped electrode electrochemical capacitor based on Spirulina platensis microalgae showed the highest specific capacitance of 99.53 Fg−1 at a scanning rate of 2.5 mV s−1 in 1 M H2SO4 electrolyte. In contrast, the supercapacitor based on an activated carbon electrode from Chlorella vulgaris microalgae showed the highest specific capacitance of 156.04 Fg−1 at a scan rate of 2.5 mV s−1 in 1 M KCl electrolyte.