11 research outputs found
Combined scanning probe microscopy and x-ray scattering instrument for in situ catalysis investigations
Catalysis and Surface Chemistr
Assessment of the Degradation Mechanisms of Cu Electrodes during the CO
Catalyst degradation and product selectivity changes are two of the key challenges in the electrochemical reduction of CO on copper electrodes. Yet, these aspects are often overlooked. Here, we combine X-ray spectroscopy, electron microscopy, and characterization techniques to follow the long-term evolution of the catalyst morphology, electronic structure, surface composition, activity, and product selectivity of Cu nanosized crystals during the CO reduction reaction. We found no changes in the electronic structure of the electrode under cathodic potentiostatic control over time, nor was there any build-up of contaminants. In contrast, the electrode morphology is modified by prolonged CO electroreduction, which transforms the initially faceted Cu particles into a rough/rounded structure. In conjunction with these morphological changes, the current increases and the selectivity changes from value-added hydrocarbons to less valuable side reaction products, , hydrogen and CO. Hence, our results suggest that the stabilization of a faceted Cu morphology is pivotal for ensuring optimal long-term performance in the selective reduction of CO into hydrocarbons and oxygenated products
Structural Dynamics of Al 2
Quantum Matter and OpticsCatalysis and Surface Chemistr
Nucleation, Alloying, and Stability of CoâRe Bimetallic Nanoparticles on Al<sub>2</sub>O<sub>3</sub>/NiAl(110)
This paper reports
on the preparation and characterization of nanostructured
Re and CoâRe/Al<sub>2</sub>O<sub>3</sub>/NiAlÂ(110) surfaces
designed as model catalysts for operando studies of FischerâTropsch
synthesis. Scanning tunneling microscopy on pure Re particles identified
strong ReâAl<sub>2</sub>O<sub>3</sub> support interaction,
resulting in uniform nucleation and growth on random point defects.
X-ray photoelectron spectroscopy confirmed the strong interaction
through a shift in the binding energy, in addition to size-dependent
final state effects. CoâRe particles were prepared by sequential
deposition of the two metals, resulting in coreâshell structures
in which the shell was (strongly) enriched with the metal deposited
second. Annealing of bimetallic particles allowed for elemental redistribution,
as was concluded from the XPS data and supported by modeling. The
annealing also resulted in sintering of bimetallic clusters. Interestingly,
the thermal stability of the CoâRe surfaces prepared by sequential
deposition of Co, followed by Re, was better than that of both pure
Co and pure Re
Recommended from our members
Graphene-Capped Liquid Thin Films for Electrochemical Operando X-ray Spectroscopy and Scanning Electron Microscopy.
Electrochemistry is a promising building block for the global transition to a sustainable energy market. Particularly the electroreduction of CO2 and the electrolysis of water might be strategic elements for chemical energy conversion. The reactions of interest are inner-sphere reactions, which occur on the surface of the electrode, and the biased interface between the electrode surface and the electrolyte is of central importance to the reactivity of an electrode. However, a potential-dependent observation of this buried interface is challenging, which slows the development of catalyst materials. Here we describe a sample architecture using a graphene blanket that allows surface sensitive studies of biased electrochemical interfaces. At the examples of near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and environmental scanning electron microscopy (ESEM), we show that the combination of a graphene blanket and a permeable membrane leads to the formation of a liquid thin film between them. This liquid thin film is stable against a water partial pressure below 1 mbar. These properties of the sample assembly extend the study of solid-liquid interfaces to highly surface sensitive techniques, such as electron spectroscopy/microscopy. In fact, photoelectrons with an effective attenuation length of only 10 Ă
can be detected, which is close to the absolute minimum possible in aqueous solutions. The in-situ cells and the sample preparation necessary to employ our method are comparatively simple. Transferring this approach to other surface sensitive measurement techniques should therefore be straightforward. We see our approach as a starting point for more studies on electrochemical interfaces and surface processes under applied potential. Such studies would be of high value for the rational design of electrocatalysts
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Revealing the Active Phase of Copper during the Electroreduction of CO2 in Aqueous Electrolyte by Correlating In Situ X-ray Spectroscopy and In Situ Electron Microscopy.
The variation in the morphology and electronic structure of copper during the electroreduction of CO2 into valuable hydrocarbons and alcohols was revealed by combining in situ surface- and bulk-sensitive X-ray spectroscopies with electrochemical scanning electron microscopy. These experiments proved that the electrified interface surface and near-surface are dominated by reduced copper. The selectivity to the formation of the key C-C bond is enhanced at higher cathodic potentials as a consequence of increased copper metallicity. In addition, the reduction of the copper oxide electrode and oxygen loss in the lattice reconstructs the electrode to yield a rougher surface with more uncoordinated sites, which controls the dissociation barrier of water and CO2. Thus, according to these results, copper oxide species can only be stabilized kinetically under CO2 reduction reaction conditions
Simultaneous scanning tunneling microscopy and synchrotron X-ray measurements in a gas environment
\u3cp\u3eA combined X-ray and scanning tunneling microscopy (STM) instrument is presented that enables the local detection of X-ray absorption on surfaces in a gas environment. To suppress the collection of ion currents generated in the gas phase, coaxially shielded STM tips were used. The conductive outer shield of the coaxial tips can be biased to deflect ions away from the tip core. When tunneling, the X-ray-induced current is separated from the regular, âtopographicâ tunneling current using a novel high-speed separation scheme. We demonstrate the capabilities of the instrument by measuring the local X-ray-induced current on Au(1 1 1) in 800 mbar Ar.\u3c/p\u3
Assessment of the Degradation Mechanisms of Cu Electrodes during the CO<sub>2</sub> Reduction Reaction
Catalyst degradation and product
selectivity changes are two of
the key challenges in the electrochemical reduction of CO2 on copper electrodes. Yet, these aspects are often overlooked. Here,
we combine in situ X-ray spectroscopy, in
situ electron microscopy, and ex situ characterization
techniques to follow the long-term evolution of the catalyst morphology,
electronic structure, surface composition, activity, and product selectivity
of Cu nanosized crystals during the CO2 reduction reaction.
We found no changes in the electronic structure of the electrode under
cathodic potentiostatic control over time, nor was there any build-up
of contaminants. In contrast, the electrode morphology is modified
by prolonged CO2 electroreduction, which transforms the
initially faceted Cu particles into a rough/rounded structure. In
conjunction with these morphological changes, the current increases
and the selectivity changes from value-added hydrocarbons to less
valuable side reaction products, i.e., hydrogen and
CO. Hence, our results suggest that the stabilization of a faceted
Cu morphology is pivotal for ensuring optimal long-term performance
in the selective reduction of CO2 into hydrocarbons and
oxygenated products
Assessment of the Degradation Mechanisms of Cu Electrodes during the CO<sub>2</sub> Reduction Reaction
Catalyst degradation and product
selectivity changes are two of
the key challenges in the electrochemical reduction of CO2 on copper electrodes. Yet, these aspects are often overlooked. Here,
we combine in situ X-ray spectroscopy, in
situ electron microscopy, and ex situ characterization
techniques to follow the long-term evolution of the catalyst morphology,
electronic structure, surface composition, activity, and product selectivity
of Cu nanosized crystals during the CO2 reduction reaction.
We found no changes in the electronic structure of the electrode under
cathodic potentiostatic control over time, nor was there any build-up
of contaminants. In contrast, the electrode morphology is modified
by prolonged CO2 electroreduction, which transforms the
initially faceted Cu particles into a rough/rounded structure. In
conjunction with these morphological changes, the current increases
and the selectivity changes from value-added hydrocarbons to less
valuable side reaction products, i.e., hydrogen and
CO. Hence, our results suggest that the stabilization of a faceted
Cu morphology is pivotal for ensuring optimal long-term performance
in the selective reduction of CO2 into hydrocarbons and
oxygenated products
Assessment of the Degradation Mechanisms of Cu Electrodes during the CO<sub>2</sub> Reduction Reaction
Catalyst degradation and product
selectivity changes are two of
the key challenges in the electrochemical reduction of CO2 on copper electrodes. Yet, these aspects are often overlooked. Here,
we combine in situ X-ray spectroscopy, in
situ electron microscopy, and ex situ characterization
techniques to follow the long-term evolution of the catalyst morphology,
electronic structure, surface composition, activity, and product selectivity
of Cu nanosized crystals during the CO2 reduction reaction.
We found no changes in the electronic structure of the electrode under
cathodic potentiostatic control over time, nor was there any build-up
of contaminants. In contrast, the electrode morphology is modified
by prolonged CO2 electroreduction, which transforms the
initially faceted Cu particles into a rough/rounded structure. In
conjunction with these morphological changes, the current increases
and the selectivity changes from value-added hydrocarbons to less
valuable side reaction products, i.e., hydrogen and
CO. Hence, our results suggest that the stabilization of a faceted
Cu morphology is pivotal for ensuring optimal long-term performance
in the selective reduction of CO2 into hydrocarbons and
oxygenated products