Carbon nanotubes as conducting support for potential Mn-oxide electrocatalysts: Influences of pre-treatment procedures

Different oxygen and nitrogen containing functional groups were created on the surface of the multi-walled carbon nanotubes. The multi-walled carbon nanotubes were treated in ultrasonic bath with sulfuric or nitric acid. Furthermore the surface texture was modified by increase of the roughness. In particular after treatment with the oxidizing nitric acid, in comparison to the H₂SO₄ or ultra-sonic treated samples, craters and edges are dominating the surface structures. Manganese oxide was deposited on the multi-walled carbon nanotubes by precipitation mechanism. Various manganese oxides are formed during the deposition process. The samples were characterized by elemental analysis, microscopy, thermal analysis, Raman spectroscopy, and by the zeta potential as well as X-ray diffraction measurements. It was shown that the deposited manganese oxides are stabilized rather by surface texture of the multi-walled carbon nanotubes than by created functional groups.