An investigation was carried out to identify the effects of incorporating Ce into ZrO2 on the catalytic activity and selectivity of Cu/CexZr1-xO2 for the hydrogenation of CO to methanol. A series of CexZr1-xO2 solid solutions was synthesized by forced hydrolysis at low pH. The resulting catalysts were characterized to determine the structure of the mixed oxide phase, the H-2 and CO adsorption capacities of the catalyst, and the reducibility of both oxidation states of both Cu and Ce. The methanol synthesis activity goes through a maximum at x = 0.5, and the activity of 3 wt% Cu/Ce0.5Zr0.5O2 catalyst is four times higher than that of 3 wt% Cu/ZrO2 when tested at total pressure of 3.0 MPa and temperatures between 473 and 523 K with a feed containing H-2 and CO (H-2/CO = 3). The maximum in methanol synthesis activity is paralleled by a maximum in the hydrogen adsorption capacity of the catalyst, an effect attributed to the formation of Ce3+-O(H)-Zr4+ species by dissociative adsorption of H-2 on particles of supported Cu followed by spillover of atomic H onto the oxide surface and reaction with Ce4+-O-Zr4+ centers. In situ infrared spectroscopy shows that formate and methoxide groups are the primary adspecies present on Cu/CexZr1-xO2 during CO hydrogenation. The rate-limiting step for methanol synthesis is the elimination of methoxide species by reaction with Ce3+-O(H)-Zr4+ species. The higher concentration of Ce3+-O(H)-Zr4+ species on the oxide surface, together with the higher Bronsted acidity of these species, appears to be the primary cause of the four-fold higher activity of 3 wt% Cu/Ce0.5Zr0.5O2 relative to 3 wt% Cu/ZrO2. (c) 2006 Elsevier Inc. All rights reserved.