Adsorption of gold subnano-structures on a magnetite(111) surface and their interaction with CO

Abstract

Gold deposited on iron oxide surfaces can catalyze the oxidation of carbon monoxide. The adsorption of gold subnano-structures on the Fe-rich termination of the magnetite(111) surface has been investigated using density functional theory. The structural, energetic, and electronic properties of gold/magnetite systems have been examined for vertical and flattened configurations of adsorbed Aun (n = 1-4) species. Single gold adatoms strongly bonded to the iron atoms of the Fe3O4(111) surface appear to be negatively charged, and consequently increase the work function. For a more stable class of larger, flattened Aun structures the adsorption binding energy per adatom is substantially increased. The structures exhibit a net positive charge, with the Au atoms binding with the oxide having distinctly cationic character. A charge transfer from the larger gold structures to the substrate is consistent with the lowering of the work function. The bonding of a CO molecule to a Au monomer on the Fe3O4(111) surface has been found nearly as strong as that to the iron site of the bare Fe-terminated surface. However, CO bonding to larger, oxide supported Aun structures is distinctly stronger than that to the bare oxide surface. Upon CO adsorption all Aun structures are cationic and CO shows a tendency to bind to the most cationic atom of the Aun cluster.

Biodiesel production from waste cooking oil

“…In particular, the enzyme is anchored thanks to the interaction with citric acid, while the presence of residual oleic acid, which exposes its a-polar tail, not only favours interfacial activation, but also probably protects the enzyme from moisture. Moreover, the heterojunction between magnetite and gold, which have different work functions [27,28], inducing a Fe 3 O 4 surface polarity modification determines an enhanced affinity with citric acid, favouring an increased stability, e.g. strong ionic interaction [29].…”

An Overview of Glycerol Electrooxidation Mechanisms on Pt, Pd and Au

“…CH 2 OHCHOHCO(ads) on the surface of Au(111) can be converted very easily into C1/C2 products, [91] which is possibly due to the lowest d‐band center among the three noble metals (−3.56 eV) [32] destabilizing RCO(ads). Besides, it has been widely reported that CO(ads) can further lower the d‐band center of Au (e. g. 3 eV for Au monomer [145] ), as the 5d bands narrows and the number of states reduces near (Fermi level), which implies a promoting effect of CO(ads) on the catalytic activity of Au. A lower d‐band center would increase the filling of the anti‐bonding orbital of the adsorbed molecule and therefore facilitates the dissociation.…”

Diels–Alder Reactions on Surface-Modified Magnetite/Maghemite Nanoparticles: Application in Self-Healing Nanocomposites

“…While the interaction with organophosphonates was studied with several other iron oxides, − there are almost no investigations on magnetite/maghemite nanoparticles. Magnetite particles seem to consist predominately of (111) surfaces, which means that the top layer consists mainly of iron ions. ,, Daou et al investigated the surface complex starting from hydroxylated magnetite at pH = 3 and found that phosphatation occurs by interaction of Fe 3+ in octahedral sites with the formation of monoprotonated bimolecular species . However, attachment mechanisms can be different, when starting from a carboxylated magnetite/maghemite surface.…”