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Item type:Publication, Access status: without files , Thermally Driven Ag-Au Compositional Changes at the Ligament Surface in Nanoporous Gold: Implications for Electrocatalytic Applications(2020-03-27); ; ; ; Nanoporous gold (NPG) is a versatile, nanoporous bulk material with applications in catalysis, sensors, energy materials, and actuation. NPG obtained from dealloying Ag-rich Au-Ag alloys has interesting applications in electrocatalysis, for which methanol oxidation is an interesting test case. Such materials always contain a content of residual silver which may play a role in activating and binding of reaction intermediates. The residual Ag that is contained in NPG due to the dealloying of a Ag-Au alloy was recently found to be present in silver-rich islands, in contrast to being homogeneously distributed. Because of the importance of residual Ag on the surface science and catalytic properties of NPG, we investigated its distribution and chemical nature with the use of X-ray photoelectron spectroscopy. During the in situ annealing, changes of the near surface content of residual Ag were observed, and they were linked to coarsening of the gold ligaments. In addition, a depth-dependent analysis of synchrotron-based XPS results confirmed the surface segregation in the near surface layers of each ligament. The available data neither confirm nor exclude a further systematic enrichment or depletion of silver in the topmost atomic layer for NPG during electrochemical treatments in KOH solution or during thermal coarsening.Publicationtype: Journal Article98 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Tailoring the Strength of Nanoporous Gold by Self-Assembled Monolayers of Alkanethiols(2018-12-28); ; ; ; Because of the large specific surface area, the properties of nanoporous metals and in particular their mechanical properties are sensitive to chemical modifications of their surfaces. Here, we exploit self-assembled monolayers (SAMs) to modify a surface of nanoporous gold and study their effect on plastic behavior. The SAMs investigated here (i) are made from alkanethiols, which consist of a sulfur headgroup that strongly binds to metal substrates, a hydrocarbon chain, and an end group, and (ii) are known to spontaneously self-organize into well-ordered, dense two-dimensional molecular films on the surface of coinage metals. Alkanethiols with various chain lengths and terminal groups were used to prepare SAMs on bulk nanoporous gold, and compression tests were performed on the SAM-modified and nonmodified macroscopic samples. Our experiments reveal a substantial, up to 50%, increase of the flow stress due to thiol adsorption. We attribute the strengthening to the adsorption locking of dislocation end points at the surface, which is mediated by the fairly strong metal-sulfur interaction. ©Publicationtype: Journal Article123