PNNL

Abstract

Water-gas shift (WGS) reaction over a series of ceria-based mixed oxides supported Cu catalysts was investigated using a combined experimental and theoretical method. The mixed rod-shaped Ce0.75M0.25O2 (M = Ti4+, Zr4+, Mn4+) solid solutions, which majorly expose the (110) and (100) facets, are synthesized by hydrothermal method and used to prepare supported Cu catalysts. It is found that the Cu/Ce0.75Ti0.25O2 (Cu-CT) exhibits the highest CO conversion in the temperature range of 150~250°C among all supported Cu catalysts. This is mainly attributed to (i) good dispersion of Cu; (ii) largest amount of moderate copper oxide; and (iii) strongest Cu-support interaction of Cu-CT. Compared to other mixed metals, periodic density functional theory calculations performed in this work further suggest that the introduction of Ti into CeO2 not only promotes oxygen vacancy formation and CO adsorption, but also facilitates the carboxyl (COOH) formation at the interface of the Cu cluster and the support, which leads to the enhanced catalytic activity of the Cu-CT toward WGS reaction.