A series of Cu-ZrO 2 catalysts with Cu content in the range of 10-70 at.% Cu (=100ÂCu/(Cu+Zr)) were prepared by coprecipitation, and their performances were tested for the water-gas-shift (WGS) reaction. The activity of the catalyst increased with Cu loading and, depending on the loading, the activity was comparable to or better than the activity of a conventional Cu-ZnO-Al 2 O 3 catalyst at low temperatures below 473 K. Characterization of the catalysts revealed that the amount of Cu + present on the catalyst surface, after being reduced by a H 2 mixture at 573 K, was well correlated with the activity of the catalyst, indicating that the Cu + species were the active sites of the WGS reaction. The easy redox between Cu 2+ and Cu + during the WGS reaction was considered to be responsible for the high activity of Cu-ZrO 2 at low temperatures. A reaction mechanism based on the redox was proposed.

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