New gold and silver-gold catalysts in the shape of sponges and sieves

Gold with a nanoporous sponge-like morphology, generated by leaching of AuAg alloys is presented as a new unsupported material system for catalytic applications. The role of residual silver for catalytic activity towards CO oxidation in the temperature range from −20 to 50°C has been investigated by comparison with Au and Au/Ag zeolite catalysts. As revealed by a systematic variation of the silver content in the zeolite catalysts, bimetallic systems exhibit a significantly higher activity than pure gold, probably due to activation/dissociation of molecular oxygen by silver. By STEM tomography we can unambiguously prove that at least some of the particles form inside the zeolite lattice.