Superior performance of Ni–W–Ce mixed-metal oxide catalysts for ethanol steam reforming: Synergistic effects of W- and Ni-dopants

Abstract

The ethanol steam reforming (ESR) reaction was studied over a series of Ni–W–Ce oxide catalysts. The structures of the catalysts were characterized using insitu techniques including X-ray diffraction, pair distribution function, X-ray absorption fine structure, and transmission electron microscopy; while possible surface intermediates for the ESR reaction were investigated by diffuse reflectance infrared Fourier transform spectroscopy. In these materials, all the W and part of the Ni were incorporated into the CeO2 lattice, with the remaining Ni forming highly dispersed nano-NiO (<2nm) outside the Ni–W–Ce oxide structure. The nano-NiO was reduced to Ni under ESR conditions. The Ni–W–Ce system exhibited a much larger lattice strain than those seen for Ni–Ce and W–Ce. Synergistic effects between Ni and W inside ceria produced a substantial amount of defects and O vacancies that led to high catalytic activity, selectivity, and stability (i.e., resistance to coke formation) during ethanol steam reforming.