  Cryptomelane has been widely applied as catalyst in oxidation reactions due
to its excellent redox properties and low cost. Here, a novel one-pot
hydrothermal synthesis using a potassium permanganate aqueous solution as
precursor and ethanol as reducing agent has successfully been developed to
obtain cryptomelane nano-oxides. This synthetic route makes it possible to
control the amount of potassium incorporated into the structure of the
cryptomelane by selecting the appropriate synthesis temperature and ethanol
initial concentration. Taking advantage of this approach, the effect of
potassium concentration on the structural stability and reducibility of the
cryptomelane, which are poorly discussed in the literature, has been studied.
We have observed that samples with low content of potassium (~11%) show high
conversions of CO to CO2 especially at low temperatures. The lower activity of
the samples with high K contents (~16%) can be ascribed to the beneficial
effect of K on the structural stability of cryptomelane in detriment of labile
oxygen on cryptomelane surface.
