Subject: How does KMnO4 and MnO2 work as catalyst in the decomposition of H2O2

I have read it before that, Mn works best as a catalyst if there are more 
vacant 3d orbital. Is it true or is there another mechanism which Mn works as a 
catalyst in the decomposition of H2O2?
Since im using two oxidation states, Mn(IV) and Mn (VII), according to the 
hypothesis above, it would mean that Mn(VII) would be the better catalyst as it 
has more vacant 3d orbital right?

Re: How does KMnO4 and MnO2 work as catalyst in the decomposition of H2O2