The common way to prepare
MnO2-catalyzed carbon is the mixing of a manganese salt and
potassium permanganate solutions in the presence of suspended
carbon substrate (2MnO4
? +3Mn2+ +2H2O→5MnO2 +4H+). The
porosity of the carbon substrate does not remain unchanged in
course of this process. The substrate undergoes modification due
to the reaction between the carbon and permanganate. As a result
of this reaction, some of closed pores turn to be opened, and some
open pores turn to be widened. This effect may be particularly
distinct after the catalyzed substrate thermo-treatment.
As-deposited MnO2 particles camouflage the pore orifices, but the
oxide particles undergo dehydration being heated, and thus shrink
and expose more carbon pore volume. This MnO2-catalized carbon
substrate behavior was demonstrated in the study of Cheng
et al. [36], which has revealed that charge capacity of the carbon,
catalyzed in KMnO4/MnSO4-process, was superior to the charge
capacity of the same carbon catalyzed by mixing with MnO2-
powder. Also it was found that the thermo-treatment (300 ?C)
enhanced the charge capacity of the KMnO4/MnSO4-catalyzed carbon;
the latter may be understood as the result of dehydration –
and hence shrinking – of KMnO4/MnSO4-prepared MnO2 particles
(MnO2 ×1.3H2O300 ?C→MnO2 ×0.26H2) [40].
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