Algal carbons hydrothermally produced from Spirulina and Chlorella with the assistance of phthalaldehyde: An effective precursor for nitrogen-containing porous carbon

A microalgal suspension of Spirulina and Chlorella in water was hydrothermally reacted at 220 degrees C for 14 h in an autoclave; this efficiently obtained hydrothermal carbons as an aggregate of non-porous spheres several microns in diameter when phthalaldehyde was added as an auxiliary condensation reagent. The algal hydrothermal carbons contained considerable quantities of nitrogen; approximately 6 wt% originated from the protein component in microalga, which could be converted to microporous carbons with a ca. 2 wt% nitrogen-content and a specific surface area of approximately 700 m2/g, via heating from room temperature to 900 degrees C under an argon atmosphere. The algal porous carbons containing pyridinic-nitrogen derived from Chlorella exhibited high activity for electrical double-layer capacitors, with capacitances of approximately 250 F/g and 200 F/g, respectively, at current densities of 0.2 A/g and 1.0 A/g in 1 M H2SO4 in a three-electrode system under galvanostatic conditions.

Automated summary

The study synthesized porous carbons from microalgae under hydrothermal conditions, and found that efficient production of porous carbons was achieved when phthalaldehyde was added. The porous carbons from microalgae contained high nitrogen content, and could be transformed into carbon materials with excellent capacitor activity by heating.