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

Abstract

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

Trends in the Catalytic CO Oxidation Activity of Nanoparticles

“…It is not that such effects may not be important, [5,20,21] but it is useful to first establish the intrinsic metal effects, [15] in particular as it has been shown experimentally that nanostructured gold with no support is also catalytically active. [22,23] The key feature of our analysis is that we compare catalytic activities of different transition and noble metals for one specific reaction, the CO oxidation.The CO oxidation reaction on close-packed fcc(111) surfaces was considered initially, which will give a dominant contribution to the total catalytic rate over large metal particles. We consider the following elementary reactions:…”

The fire assay reloaded

“…For this reasons, the cornet appears brown in colour [18][19][20][21][22]. This very interesting behaviour of nanoporous gold and gold nanoparticles has been studied also for many different applications, such as monitoring body fluids, new electronic devices and decorative effects [23][24][25][26][27][28][29][30][31].…”

Thermal Stability of Nanoporous Raney Gold Catalyst

“…Since then, further examples of the catalytic efficacy of nanoporous Au have been reported, mostly in sponges prepared from AuxAg alloys [33][34][35]. There have been several subsequent studies of these materials as catalysts for reactions as diverse as CO oxidation [33,35] and oxidative coupling of methanol to methyl formate [36].…”

“…There have been several subsequent studies of these materials as catalysts for reactions as diverse as CO oxidation [33,35] and oxidative coupling of methanol to methyl formate [36]. In general, however, there is evidence that the catalytic activity in the nanoporous gold produced from (Au, Ag) precursors is correlated with the small quantity of Ag remaining after de-alloying rather than to the gold on its own [36][37][38].…”