2 results
Filters
Settings
Now showing1 - 2 of 2
- Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Surface-to-Volume Ratio Drives Photoelelectron Injection from Nanoscale Gold into Electrolyte(2019-04-05); ; ; ; Hot charge carriers from plasmonic nanomaterials currently receive increased attention because of their promising potential in important applications such as solar water splitting. While a number of important contributions were made on plasmonic charge carrier generation and their transfer into the metal's surrounding in the last decades, the local origin of those carriers is still unclear. With our study employing a nanoscaled bicontinuous network of nanoporous gold, we take a comprehensive look at both subtopics in one approach and give unprecedented insights into the physical mechanisms controlling the broadband optical absorption and the generation and injection of hot electrons into an adjacent electrolyte where they enhance electrocatalytic hydrogen evolution. This absorption behavior is very different from the well-known localized surface plasmon resonance effects observed in metallic nanoparticles. For small ligament sizes, the plasmon decay in our network is strongly enhanced via surface collisions of electrons. These surface collisions are responsible for the energy transfer to the carriers and thus the creation of hot electrons from a broad spectrum of photon energies. As we reduce the gold ligament sizes below 30 nm, we demonstrate an occurring transition from absorption that is purely exciting 5d-electrons from deep below the Fermi level to an absorption which significantly excites "free" 6sp-electrons to be emitted. We differentiate these processes via assessing the internal quantum efficiency of the gold network photoelectrode as a function of the feature size providing a size-dependent understanding of the hot electron generation and injection processes in nanoscale plasmonic systems. We demonstrate that the surface effect, compared with the volume effect, becomes dominant and leads to significantly improved efficiencies. The most important fact to recognize is that in the surface photoeffect presented here, absorption and electron transfer are both part of the same quantum mechanical event.Publicationtype: Journal Article289 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Electrocatalytic methanol oxidation with nanoporous gold: microstructure and selectivity(Royal Society of Chemistry (RSC), 2017-10-17); ; ; ; The properties of Nanoporous Gold (NPG) obtained by the selective dissolution of Ag from an Au–Ag alloy can be tuned by the details of its fabrication, and specifically the residual Ag content is correlated to the ligament size of the material. We link this correlation to methanol electro-oxidation. Specifically, two different NPG types (obtained by potentiostatic dealloying) are compared with one obtained by free corrosion. They show remarkable differences in activity. Quantitative product analysis reveals that NPG shows nearly selective oxidation of CH3OH to HCOO− when NPG is used as an active electrode in contrast to planar Au. This trend can further be enhanced when applying finer nanoporous structures that are linked to a higher Ag content. X-ray photoelectron spectroscopy (XPS) reveals changes in the nature of residual Ag from which we conclude that Ag is not a passive component in the methanol oxidation process.Publicationtype: Journal ArticleScopus© Citations 57 377 336