Nanostructured Mn-doped ceria solid solutions for efficient oxidation of vanillyl alcohol

Abstract

Ceria is the hub of constant and diverse research interest due to its wide industrial applications. In the present work, we have developed Mn-doped CeO2 catalysts for vanillyl alcohol oxidation. Accordingly, we synthesized nanostructured Mn-doped CeO2 catalysts with various concentration of MnOx by an economical coprecipitation method and characterized using XRD, ICP-OES, BET surface area, Raman spectroscopy, TEM, XPS, and H2-TPR techniques. XRD and TEM results confirmed formation of nanocrystalline solid solutions with the incorporation of Mn into ceria lattice. ICP-OES analysis confirmed actual amount of MnOx loadings in the respective catalysts. The BET surface area of CeO2 significantly enhanced after the incorporation of MnOx dopant. Raman results disclosed that the incorporation of MnOx into ceria lattice greatly enhances the oxygen vacancies, which are responsible for the improved catalytic activity. XPS analysis revealed that Ce and Mn exist in +3, +4 and +2, +3, +4 oxidation states, respectively, on the surface of the samples. H2-TPR results showed pronounced enhancement in the reduction of CeO2 by MnOx doping. Catalytic activity studies confirmed that among all the catalysts, the Ce0.7Mn0.3O2−δ showed superior activity for vanillyl alcohol oxidation with 89% conversion and 95% selectivity, which could be attributed to higher concentration of oxygen vacancies, a high BET surface area, low temperature reducibility, and facile synergetic interaction between CeO2 and MnOx.