2 research outputs found
Experimental and Theoretical Investigation of the Restructuring Process Induced by CO at Near Ambient Pressure: Pt Nanoclusters on Graphene/Ir(111)
The
adsorption of CO on Pt nanoclusters grown in a regular array
on a template provided by the graphene/Ir(111) Moiré was investigated
by means of infrared-visible sum frequency generation vibronic spectroscopy,
scanning tunneling microscopy, X-ray photoelectron spectroscopy from
ultrahigh vacuum to near-ambient pressure, and <i>ab initio</i> simulations. Both terminally and bridge bonded CO species populate
nonequivalent sites of the clusters, spanning from first to second-layer
terraces to borders and edges, depending on the particle size and
morphology and on the adsorption conditions. By combining experimental
information and the results of the simulations, we observe a significant
restructuring of the clusters. Additionally, above room temperature
and at 0.1 mbar, Pt clusters catalyze the spillover of CO to the underlying
graphene/Ir(111) interface
Probing the Gold/Water Interface with Surface-Specific Spectroscopy
Water is an integral component in electrochemistry, in
the generation
of the electric double layer, and in the propagation of the interfacial
electric fields into the solution; however, probing the molecular-level
structure of interfacial water near functioning electrode surfaces
remains challenging. Due to the surface-specificity, sum-frequency-generation
(SFG) spectroscopy offers an opportunity to investigate the structure
of water near working electrochemical interfaces but probing the hydrogen-bonded
structure of water at this buried electrode–electrolyte interface
was thought to be impossible. Propagating the laser beams through
the solvent leads to a large attenuation of the infrared light due
to the absorption of water, and interrogating the interface by sending
the laser beams through the electrode normally obscures the SFG spectra
due to the large nonlinear response of conduction band electrons.
Here, we show that the latter limitation is removed when the gold
layer is thin. To demonstrate this, we prepared Au gradient films
on CaF2 with a thickness between 0 and 8 nm. SFG spectra
of the Au gradient films in contact with H2O and D2O demonstrate that resonant water SFG spectra can be obtained
using Au films with a thickness of ∼2 nm or less. The measured
spectra are distinctively different from the frequency-dependent Fresnel
factors of the interface, suggesting that the features we observe
in the OH stretching region indeed do not arise from the nonresonant
response of the Au films. With the newfound ability to probe interfacial
solvent structure at electrode/aqueous interfaces, we hope to provide
insights into more efficient electrolyte composition and electrode
design