Raman in situ characterization of the species present in Co/CeO sub(2) and Co/ZrO sub(2) catalysts during the COPrOx reaction

The in situ Raman spectroscopy constitutes a powerful procedure to characterize catalytic surfaces under reaction conditions. In this work, we studied the species present in Co/CeO sub(2) and Co/ZrO sub(2) catalysts during the COPrOx reaction carried out between room temperature and 500 degree C. For both catalysts, TPR and Raman results suggest that a redox mechanism proceeds in which the reduction step with either hydrogen or CO is the rate-limiting step. The CeO sub(2) support is better than the ZrO sub(2) one because the former accelerates the surface exchange between reduced and oxidized species due to the high mobility of surface lattice oxygen and the presence of oxygen vacancies. The Ce super(4+) + Co super(2+) reversible reaction Ce super(3+) + Co super(3+) process acts as a buffer effect by which Co super(3+), which is the active species in this reaction, is always present even in a reducing atmosphere, as shown by in situ Raman characterization.