Branched mesoporous Mn3O4 nanorods: facile synthesis and catalysis in the degradation of methylene blue.

Branched MnOOH nanorods with diameters in the range of 50-150 nm and lengths of up to tens of micrometers were prepared by using potassium permanganate (KMnO(4)) and PEG 400 (PEG=polyethylene glycol) as starting materials through a simple hydrothermal process at 160 °C. After annealing at 300 °C under a N(2) atmosphere for 5 h, MnOOH nanorods became gradually dehydrated and transformed into mesoporous Mn(3)O(4) nanorods with a slight size-shrinking. The as-obtained mesoporous Mn(3)O(4) nanorods had an average surface area of 32.88 m(2) g(-1) and a mean pore size of 3.7 nm. Through tuning the experimental parameters, such as the annealing atmosphere and temperature, β-MnO(2), Mn(2)O(3), Mn(3)O(4), MnO, and Mn(5)O(8) were selectively produced. Among these structures, mesoporous Mn(3)O(4) nanorods were efficient for the catalytic degradation of methylene blue (MB) in the presence of H(2)O(2) at 80 °C.