Oxidation of an organic dye catalyzed by MnOx nanoparticles

We present a study on the catalytic oxidation of the organic dye morin by hydrogen peroxide in the presence of manganese oxide nanoparticles in aqueous solution. The ultrathin manganese oxide nanoparticles consist of c*-disordered potassium birnessite and are immobilized on spherical polyelectrolyte brushes. The catalytic activity of these composite particles was investigated using the oxidation of morin by hydrogen peroxide as a model reaction. The oxidative degradation of morin was followed by UV/vis spectroscopy leading to an apparent rate constant kapp. We propose a modeling of the results in terms of a Langmuir–Hinshelwood model. kapp can be related to the kinetic constant k and to the apparent adsorption constants of H2O2 and morin. Based on this model, the dependence of kapp on temperature can be traced back to the activation energy of the rate constant k and the adsorption enthalpies of both educts on the surface of the nanoparticles.

The catalysis of the oxidation of morin by H2O2 in the presence of colloidal manganese oxide particles is studied. It is demonstrated that this reaction proceeds on surface of the MnOx particles.Figure optionsDownload high-quality image (101 K)Download as PowerPoint slideResearch highlights
► We model the catalytic oxidation of morin by hydrogenperoxide in the presence of colloidal MnOx in a quantitative fashion.
► We demonstrate that the ultrathin MnOx particles present highly active catalysts for this oxidation.
► We demonstrate that the rate-determining step takes place on the surface of the colloidal MnOx.
► We analyze the dependence of this reaction on temperature and determine the respective kinetic and thermodynamic parameters.