Origins of catalysis for CO oxidation on porous Ag fabricated by leaching of intermetallic compound Mg₃Ag

In order to investigate origins of catalysis for CO oxidation on a bulk-type Ag catalyst, porous Ag catalysts were prepared by the leaching of Mg from an intermetallic compound, Mg₃Ag. Compared with a commercial Ag powder, the porous Ag catalyst exhibited significantly high catalytic activity for CO oxidation. Although the Ag powder showed low catalytic activity for CO oxidation without hysteresis, the catalytic activity of the porous Ag catalyst was significantly increased after the heating process, even though the surface area was decreased. From different structural characterizations, it was found that structural defects introduced during leaching effectively improve the catalytic activity by increasing the number of active sites. Therefore, it is concluded that the dominant factors for catalysis on porous Ag are not only the surface area of the material, but also twin boundary defects, structural strain and residual Mg species (e.g., MgO_x).