The Structure of the Cu–CuO Sites Determines the Catalytic Activity of Cu Nanoparticles

The effect of nanosized ceria on supported Cu nanoparticles was investigated at an atomic level and correlated to the catalytic activity on the water–gas shift reaction (WGSR) rate. For Cu/Al2O3, increasing the Cu nanoparticle size leads to a decrease in the oxygen coverage and an increase in the bond length of Cu–O. When different loadings of nanosized ceria are introduced to the Cu/Al2O3 catalysts, no significant change occurred in the Cu particle size, the Cu–Cu bond length, or the oxygen coverage. However, ceria is able to interact with the Cu nanoparticles to increase the Cu–O bond length, and a linear correlation between ceria loading, Cu–O bond length, and WGSR rate was found. Hence, while previous reports claim that ceria leads to Cu nanoparticle stabilization or interface active sites, we have shown that the ceria tailors the Cu–O bond length, which has been shown to be a determinant of the WGSR rate.