Enhanced manganese dioxide supercapacitor electrodes produced by electrodeposition

Electrodeposited thin films of manganese dioxide, prepared using chronoamperometry on a platinum substrate in an electrolyte of MnSO4 in H2SO4, possess a significantly higher capacitance compared to the literature materials (>2000 F g−1 which is at least a 250% increase in performance) when cycled over a 0.8 V potential window in an aqueous electrolyte of 0.5 M Na2SO4. This excellent performance is discussed in terms of the manganese dioxide electrodeposition mechanism, in particular the growth mechanism under the preferred slow mass transport of electro-active species, and its effects on morphology. Furthermore, the origin of the enhanced capacitance is discussed, in which case we have proposed arises from contributions made by hydroxyl groups on the manganese dioxide nano-particulate surface, in addition to the fast redox reactions that are necessary for pseudo-capacitance.

► In this work we have used chronoamperometry to produce very thin films of manganese dioxide for use as supercapacitor electrodes.
► The performance of these electrodes has been shown to be excellent, with capacitances of over 2000 F g−1 routinely able to be achieved.
► This performance was discussed in terms of the synthesis conditions used, with a highly acidic, non-diffusion limited environment being preferred for optimum performance.
► The source of this high capacitance has been discussed in terms of manganese dioxide surface chemistry.