Effect of surfactant structure on charge storage properties in Co3O4-based electrodes

Co3O4 powders are synthesized by a controllable microwave process in the presence of nonionic surfactants characterized by various structures. The influence of the surfactant structure on the charge storage performance of Co3O4 -based electrode is commented through the specific surface area and morphology of Co3O4 powder. In the absence of surfactants, Co3O4 layers are self-organized into microspheres. When linear PEG 2000 or Triton X100 polymers are used as surfactants, Co3O4 microspheres unfold into particles. However, a nanorods-like morphology is obtained with the multi-branched Tween 20 surfactant. Such a unique architecture exhibits remarkable electrochemical performance with high capacity and suitable cycle life after 2000 cycles in 3 M KOH aqueous solution. Increasing the specific surface area results in the improvement of the electrochemical performance. The specific capacity values deduced from cyclic voltammetry experiments are found to increase in the following order: Co3O4 -without surfactant (60 mAh g−1) < Co3O4-Triton X100 < Co3O4-PEG 2000 < Co3O4-Tween 20 (126 mAh g−1). The exceptional charge storage performance of Co3O4 elaborated with Tween 20 is also confirmed galvanostatically in term of high capacity retention. It shows that 70% of the capacity is maintained upon a gradual increase of the applied current density from 5 to 15 A g−1.