In Situ Raman Spectroscopic Study of Species in Co-MnCeOx Catalysts under COPrOx Reaction Conditions

Abstract

This work is focused on the study of Co-MnCeOx catalysts by in situ Raman spectroscopy, under COPrOx conditions, and aims to establish a correlation with the catalytic results of different catalytic formulations. Through XRD, the catalysts structures were explored, and the oxidation states and relative concentrations of surface species were analyzed by XPS. Catalysts were prepared with Co (10 wt %) and different Mn concentrations. The more active catalyst contains 2.5 wt % of Mn and Co/Ce ≈ 1 (CO conversion 99.5%, 150–180 °C). The Co-Mn2.5Ce catalyst is composed of Co3O4 spinel, Mn inserted in the CeO2 lattice, and probably MnOx dispersed, which remains stable up to 250 °C under reaction conditions. XRD results confirm the crystalline structure of Co3O4 spinel; however, there was no evidence of crystalline phases of MnOx oxides. A lower lattice parameter suggests the insertion of Mnn+ ions in the ceria framework. The catalytic surface is composed of Co3+-Co2+ belonging to Co3O4 and Ce4+ of ceria and Mn4+-Mn3+ species.