Synthesis, characterization and catalytic activity of birnessite type potassium manganese oxide nanotubes and nanorods

Birnessite-type manganese oxide nanotubes and nanorods were synthesized via a calcination process using manganese acetate and potassium hydroxide as precursors in presence of polyethylene glycol-melamine-formaldehyde. As-prepared products were characterized by XRD, FT-IR, FE-SEM, TEM, SA-ED, HR-TEM, Brunauer-Emmett-Teller (BET) and TGA analyses. The influences of reaction temperature and time on the morphology of manganese oxide nanocrystals were investigated. The oriented attachment-thermodynamical (OA-TD) process is suggested to describe the transition from tube to rod structure. Their capability of catalytic degradation of safranin O was compared. The results indicate that birnessite-type manganese oxide nanotube has higher catalytic activity for than nanorod crystal in aqueous solution, because it has a larger surface area. The decomposition of safranin O follows pseudo-first order kinetics and is markedly affected by pH. (C) 2012 Elsevier B.V. All rights reserved.