Hydrogen production from oxidative steam reforming of ethanol on nickel-substituted pyrochlore phase catalysts

A series of Ni-substituted pyrochlore oxides of La₂Ce_2−xNi_xO_7−δ (x = 0.0–0.45) is prepared and their catalytic performance is studied. All compounds are characterized by X-ray powder diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and temperature-programmed reduction (TPR). Based on the XRD and XPS analyses, Ni is incorporated into the pyrochlore structure and induces the formation of Ce³⁺ ions. The reduction behavior and catalytic performance are directly related to the Ni content. The H₂ consumption in the TPR and H₂ production increases with the increased Ni content. The catalytic properties of these catalysts in the oxidative steam reforming of ethanol (OSRE) are investigated. The highest catalytic activity is obtained for the x = 0.45 sample, with a hydrogen selectivity of 82.60(5)% and the most stable catalyst is x = 0.2 with an average hydrogen selectivity of 79.0(4)%. The improved catalytic behavior can be attributed to the synergetic effect of cerium and nickel ions in the pyrochlore framework, which induces oxygen vacancies and reduces carbon formation.