Effect of Re addition on the activities of Co/CeO2 catalysts for water gas shift reaction

The catalytic activities of Re–Co/CeO2 bimetallic catalysts for the water gas shift (WGS) reaction were investigated and compared with activities of Co/CeO2. It was found that the rate of WGS reaction over Re–Co/CeO2 bimetallic catalysts was higher than that of a single catalyst of Co on ceria. It seems that Re influences the catalysts and the catalyst performance in several ways. XRD and Raman spectroscopy results indicate that metal oxides were dispersed on ceria surface and H2-chemisorption indicated better dispersion of Co on the ceria surface upon addition of Re. X-ray absorption near edge structure (XANES) spectra of Re–Co/CeO2 indicate that Re promotes the reduction of surface ceria to Ce2O3 and provides oxygen vacancies that facilitate the redox process at the surface. XANES also indicated that electron densities were withdrawn from Co d-state to Re, leading to weaker Co-adsorbate bonds. All of these effects contribute to an increase in the WGS reaction rate.

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► Activity of Co/CeO2 increases upon addition of Re.
► XANES results indicate movement of electrons from Co to Re d-orbitals.
► Lowering of back-donated electrons of Co orbitals leads to weaken of Co–CO bond.
► Re promotes the reduction of CeO2 to Ce2O3 leading to oxygen vacancies that facilitates WGS reaction.