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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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In this study, the ideal alloying element (among Cr, V, and Mo carbides) to enhance the resistance to hydrogen embrittlement (HE) in a tempered martensitic steel was investigated. Four types of steels were designed to contain cementites, Cr-rich M7C3 carbides, V carbides, and Mo carbides, respectively. These steels were tailored to possess a comparable tensile strength (~1.6 GPa). The HE resistances of these steels were evaluated through the slow strain rate test and cyclic corrosion test. The results showed an enhanced HE resistance, characterized by a high notch fracture strength after hydrogen charging, in the samples containing V carbides and Mo carbides. In particular, Mo carbide was regarded as the most ideal alloying element for HE resistance because of the high resistivity parameter, inhibited hydrogen penetration, and suppressed strength loss by internal hydrogen.