Cu-ZrO2 catalysts for water-gas-shift reaction at low temperatures

A series of Cu–ZrO2 catalysts with Cu content in the range of 10–70 at.% Cu (=100×Cu/(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–Al2O3 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 H2 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 Cu2+ and Cu+ during the WGS reaction was considered to be responsible for the high activity of Cu–ZrO2 at low temperatures. A reaction mechanism based on the redox was proposed.