Ni/CeO2: a promising catalyst for water-gas shift

Abstract

Hydrogen appears to be the best answer for the limited fossil fuel resources. The water-gas shift (WGS) reaction is a key step in the production of clean hydrogen. Noble metal (Au, Pd, Pt) clusters supported on reducible oxides have emerged as a potentially new generation of WGS catalysts. The substitution of the noble metals by less expensive alternatives without compromising performance represents a big challenge. Ni/CeO2 systems were shown to be promising catalysts, but their activity strongly depends on the metal coverage. At medium and large coverages, they catalyze methane production, whereas at small coverage they are efficient for the WGS reaction. A fundamental understanding of this effect is paramount for a rational design of Ni-based catalysts. Here, we discuss the interaction of Ni clusters of varying size with the CeO2(111) surface and the chemisorption properties for C and CO. In doing this we are able to explain the coverage dependence of the chemical reactivity. Furthermore, we show that Ni/CeO2(111) is able to dissociate water - a crucial step in the WGS process.