Synthesis of nanosized MnO2 prepared by the polyol method and its application in high power supercapacitors

Over the last years, the different polymorphs of MnO2 have been intensely studied as alternative compounds to amorphous hydrous RuO2 as supercapacitor electrode materials. In the present work, nanosized birnessite-type MnO2 platelets were synthesized via the polyol method followed by a subsequent ligand removal with NaOH. The resulting compound is easily dispersible in polar solvents, thus allowing the preparation of stable dispersions (2-3 days) that could be used in thin electrode preparation. The capacitance of the synthesized product was 130 F g(-1) in a potential window of 0.8 V at a scan rate of 2 mV s(-1). The synthesized material was also studied using a cavity microelectrode to evaluate the electro-chemical performance of the nanostructured oxide at high scan rates. Cyclic voltammetry measurements were successfully carried out both in the previous potential window between 0.1 and 0.9 V (vs. SHE) and in a larger potential window between -0.6 and 1.1 V (vs. SHE) from 0.1 and up to 1,000 mV s(-1). Therefore, herein prepared material could be potentially used for high power applications, although further work should be carried out to upscale such compound without compromising the performance.