Article ID: 010401
The suspension of a powder of microalgae (Spirulina or Chlorella) biomass, terephthalaldehyde condensation accelerator, and Mg pre-template (MgCl2, Mg(OAc)2, Mg(OH)2, or MgO mixture) in water was hydrothermally reacted at 220 °C for 14 h in an autoclave. The MgCl2 additive changed the pH of the reaction solution to acidic, resulting in a reduced yield of the insoluble hydrothermal product. By contrast, Mg(OAc)2, Mg(OH)2, and the MgO mixture kept the pH of the solution neutral to weakly alkaline, which produced a large amount of non-porous hydrothermal carbons. The particulate hydrothermal carbons were carbonized after or before removal of the Mg template by acid washing via heating up from room temperature around 25 °C to 900 °C under an Ar atmosphere. The resulting Mg-free algal carbonized materials were N-containing porous carbons with specific surface areas ranging from 200−1500 m2/g, ratios of mesopore volume/total pore volume ranging from 60−90%, and electrochemical capacitances in the range of 150−320 F/g at 0.1 A/g in 1M H2SO4.
