The effect of the addition of various amounts of sulfates to a zirconia support and its possible role during the Au deposition-precipitation step was examined. The high activity showed by the Au/ZrO2 catalysts in the WGS reaction was enhanced by the action of sulfates on the support. SO42- addition to zirconia brings a higher gold dispersion due to (i) the larger surface area and (ii) the positive role of SO42- groups that determine the deposition of Au in the form of highly dispersed non-metallic gold clusters in close contact with the support. (c) 2010 Elsevier B.V. All rights reserved.