Controllable adjustment of oxygen contents in activated carbons and oxygen effect on electrochemical performances in supercapacitors

Abstract

Summary In this work, oxygen‐doped activated carbons (ACs) are derived from glucose by hydrothermal synthesis (HTS) and a two‐step consecutive activation/treatment. The first KOH activation leads to the formation of well‐developed hierarchical porous structure. The second H2O‐steam treatment controls the fraction of oxygen contents ranging from 3.35 to 10.43 at% by regulating the treatment time and temperature. We propose a reaction for the oxygen reduction during the H2O‐steam treatment, of which the resultant reaction rate increases with the increase of the treatment temperature. The nominal activation energy for the reaction is 18.79 kJ/mol. The symmetric supercapacitors with the ACs of the highest oxygen content exhibit the best electrochemical performances of an optimum specific capacitance of 240.49 F/g in the electrolyte of 1 M H2SO4. However, the symmetric supercapacitors with the ACs of the lowest oxygen content exhibit the best electrochemical performances of an optimum specific capacitance of 171.81 F/g in the organic electrolyte of 1 M Et4BF4 in AN.