Catalytic activities of Re–Ni/CeO2 bimetallic catalysts for water gas shift reaction

The catalytic activities of Re–Ni/CeO2 bimetallic catalysts were investigated for the water gas shift reaction in the temperature range of 150–600 °C. Re–Ni/CeO2 bimetallic catalysts were prepared by the incipient wetness impregnation method with aqueous solutions of Ni(NO3)2·6H2O and NH4ReO4. The amount of Re was kept constant at 1 wt%, while that of Ni was varied at 1.0, 2.5, 5.0, 7.5 and 10.0 wt%. The activities of all doped samples were tested in a flow reactor with initial mixed feed gas of 5% CO and 10% H2O. Re–Ni/CeO2 bimetallic catalysts showed a higher rate of WGS reaction than Ni/CeO2 monometallic catalysts. The results from XRD and Raman spectroscopy indicate that doped oxide species were dispersed on the ceria surface and H2 chemisorption indicated better dispersion of Ni on the ceria surface with the addition of Re. X-ray absorption near edge structure (XANES) of the Ce L3 edge indicated that Re promotes the reduction of Ce4+ at the surface and facilitates the WGS redox process. XANES results also indicated movement of electron density from Ni to Re leading to an enhancement of CO adsorption on the Ni active sites. All of these effects contributed to an increase of the WGS reaction rates.

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► Activity of Ni/CeO2 increases upon addition of Re.
► Re promotes better dispersion of nickel oxide on the ceria support.
► Re promotes the reduction of CeO2 to Ce2O3 leading to oxygen vacancies that facilitates WGS reaction.
► XANES results indicate movement of electrons from Ni to Re d-orbital.
► Lowering of Ni d-electrons leads to easier CO adsorption.