Activated chitosan microspheres as air cathode catalyst for high power production in microbial fuel cells

This study aimed to modify chitosan microspheres to have large specific surface area as cathode catalysts in microbial fuel cell. Nitrogen-rich chitosan microspheres were first prepared and were used as precursors to prepare the activated carbon materials. The activation effects of KOH and activation temperature on the graphitization degree, specific surface area and electrochemical performance were investigated. The materials were characterised through various microscopic analyses and the electrochemical properties of the materials as cathode catalyst were also investigated. Before and after the activation, the materials remained in microspheric morphology, shown by SEM measurement, while the specific surface area of the activated material increased significantly and reached 1562 m ^2 g ^−1 measured by BET. The graphitization degree of the material showed synchronized increase with calcination temperature, which was detected by Raman spectroscopy. The materials activated were rich in nitrogen, revealed by XPS for elemental analysis. When activated at the temperature of 850 °C, the material demonstrated lower internal resistance (0.6 Ω cm ^−2 ), higher alternating current density (24.27 × 10 ^–4 A·cm ^−2 ) and the highest power density (1531 ± 51 mW·m ^−2 ) which was 1.4 times that of the original carbon felt. It was illustrated by the electrochemical tests that the material prepared from the precursor chitosan microspheres as cathode catalyst has the high activity of oxygen reduction reaction in MFCs.