Combined UHV/high-pressure catalysis setup for depth-resolved near-surface spectroscopic characterization and catalytic testing of model catalysts

Mayr, Lukas; Rameshan, Raffael; Klötzer, Bernhard; Penner, Simon; Rameshan, Christoph

doi:10.1063/1.4874002

Cited by 16 publications

(17 citation statements)

References 28 publications

(18 reference statements)

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“…Optical and electron micrographs of the catalyst before and after MSR are given in the Supporting Information (Figure S13 and S14). Temperature‐programmed methanol steam reforming experiments were performed by using an UHV‐attached high‐pressure batch reactor with continuous MS detection . The following starting conditions were applied: 12 mbar methanol, 24 mbar water, 8 mbar Ar, and 956 mbar He.…”

Section: Figurementioning

confidence: 99%

“…According to Figure 2, the maximum formation rate of CO 2 increases and the onset temperature for CO 2 formation decreases by running four identical catalytic MSR cycles (Figure 2a nd Figure S1). As shown in Figures 1, 3, and 4, activation is morphologically characterized by oxidative segregation as ac onsequence of decomposition of the intermetallic compound Cu 51 Zr 14 and subsequent( partial)Z rs urface hydroxylation (Zr 3d, BE = 183.1 eV [17] ). Oxidation of the intermetallic compound thus occurs without passivatingt he surfacew ith ZrO 2 .T he direct comparison to the Cu/Zn system,a lready characterized catalytically in the same experimental setup, [8] reveals that activation of the reaction-induced Cu/Zr material leads to a" self-stabiliz-ing" state that is much more stable, and no oxidative/thermal Cu sintering was observed.…”

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confidence: 99%

“…Ab imetallic Cu/Cu 51 Zr 14 precatalyst,a ctivated in situ, for hydrogen generation from methanol and water providesv ery high CO 2 selectivity (> 99.9 %) and high H 2 yields. Referenced to the geometrics urface area of our model surface, highera ctivity of at least one order of magnitude was observed in comparison to supportedC u/ZrO 2 and Cu/ZnO/ZrO 2 catalysts.…”

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Boosting Hydrogen Production from Methanol and Water by in situ Activation of Bimetallic Cu−Zr Species

et al. 2016

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Ab imetallic Cu/Cu 51 Zr 14 precatalyst,a ctivated in situ, for hydrogen generation from methanol and water providesv ery high CO 2 selectivity (> 99.9 %) and high H 2 yields. Referenced to the geometrics urface area of our model surface, highera ctivity of at least one order of magnitude was observed in comparison to supportedC u/ZrO 2 and Cu/ZnO/ZrO 2 catalysts. Evolution of structurala ctivation monitored by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electron microscopy indicatest ransformation of the bimetallic Cu/Cu 51 Zr 14 precatalyst into an active, selective, and self-stabilizing state with coexistence of dispersed Cu and partially hydroxylated tetragonal ZrO 2 .The outstanding performance is assigned to the presence of ah igh interface-site concentration following in situ decompositiono ft he intermetallic compound. These actives ites result from the cooperation of Cu, responsible for methanol activation,a nd tetragonal ZrO 2 ,w hich activates the water by surface hydroxylation.Copper-based catalysts are widely used for technical applications in methanolc hemistry,w ell-known examples include methanol synthesis from syngasw ith an optimized CO/CO 2 ratio, hydrogenation/photoreduction of CO 2 to produce "renewable" methanol, and methanol steam reforming (MSR) as the reversal of the synthesis reactionf rom CO 2.[1] The ability to control product selectivity is ak ey criterion for technical usage. Therefore, to realize the efficient on-boardp roduction of clean hydrogen in, for example, automotive applications, the key targets for MSR are high CO 2 selectivity,l ow CO content,a nd maximum H 2 yield in the reformate.[2] With respect to the catalytic functiono fZ rO 2 in MSR, the simple addition of ZrO 2 to the conventionally used Cu/ZnO catalysts overcomes the inherent drawback of purely ZnO-based catalysts,t hat is, the poor sinterings tability.[2] Beneficial synergistic effectsf or methanol synthesis have also been described for Cu/Zn and the ternary Cu/Zn/Al system prepared by ac o-precipitation technique.[3]Synergistic Cu-ZrO 2 interactions have also been reported for Cu/ZrO 2 catalysts without ZnO, involving CuÀOÀZr bonds at the phase boundary. The Cu-ZrO 2 interactions are believed to play ac rucial role in steering the methanol reforming reaction to maximum CO 2 selectivity.[4] Specifically,ananocrystalline Cu/ tetragonal ZrO 2 catalyst synthesized by ap olymer templating technique [5] was reported to be more active, selective, and stable in MSR than the technical Cu/ZnO/Al 2 O 3 methanol synthesis catalyst.[6] Although the beneficial effects of the redox chemistry of Cu and the Cu 0 /Cu oxidized ratio at the interface has been suggesteda sa ni mportants electivity descriptor,a longside disorder and strain phenomena within the metallicC u phase, [2] ac ontradictingi nfluence hasa lso been reported. Both beneficial [4a, b] and adverse [4d] effectso ft he reducibility of Cu can be found in the literature. Nevertheless, any influence appears strongly connected to the quantity...

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Section: Figurementioning

confidence: 99%

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Boosting Hydrogen Production from Methanol and Water by in situ Activation of Bimetallic Cu−Zr Species

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“…For discussion about mass and heat transport limitations, we refer to a thorough discussion of the catalytic setup in Ref. [31].…”

Section: Catalytic Measurementsmentioning

confidence: 99%

“…For the former, sample preparation and characterization was performed in a combined preparation/analysis chamber with attached recirculating batch reaction cell operating at ambient pressures, described in more detail elsewhere (base pressure in the low 10 −9 mbar range) [31]. The sample is heated via e-bombardment, where electrons are ejected from a triple-filament emitter (operated with 30 W heating power) set to −500 V, while the sample is set to +300 V. The electron impact heating power is controlled via the filament emission current.…”

Section: Uhv Setupmentioning

confidence: 99%

A Comparative Discussion of the Catalytic Activity and CO2-Selectivity of Cu-Zr and Pd-Zr (Intermetallic) Compounds in Methanol Steam Reforming

et al. 2017

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Abstract:The activation and catalytic performance of two representative Zr-containing intermetallic systems, namely Cu-Zr and Pd-Zr, have been comparatively studied operando using methanol steam reforming (MSR) as test reaction. Using an inverse surface science and bulk model catalyst approach, we monitored the transition of the initial metal/intermetallic compound structures into the eventual active and CO 2 -selective states upon contact to the methanol steam reforming mixture. For Cu-Zr, selected nominal stoichiometries ranging from Cu:Zr = 9:2 over 2:1 to 1:2 have been prepared by mixing the respective amounts of metallic Cu and Zr to yield different Cu-Zr bulk phases as initial catalyst structures. In addition, the methanol steam reforming performance of two Pd-Zr systems, that is, a bulk system with a nominal Pd:Zr = 2:1 stoichiometry and an inverse model system consisting of CVD-grown ZrO x H y layers on a polycrystalline Pd foil, has been comparatively assessed. While the CO 2 -selectivity and the overall catalytic performance of the Cu-Zr system is promising due to operando formation of a catalytically beneficial Cu-ZrO 2 interface, the case for Pd-Zr is different. For both Pd-Zr systems, the low-temperature coking tendency, the high water-activation temperature and the CO 2 -selectivity spoiling inverse WGS reaction limit the use of the Pd-Zr systems for selective MSR applications, although alloying of Pd with Zr opens water activation channels to increase the CO 2 selectivity.

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Preparation of Ni and NiCu/Yttria‐Stabilized Zirconia Model Electrodes with Optimized Triple‐Phase Boundary Geometry for Fundamental Operando Spectroscopic Studies

Thurner,

Haug,

Winkler

et al. 2023

Small Structures

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Solid oxide cell technologies play a pivotal role in the realm of renewable energy storage, guiding us through the journey toward decarbonization. Understanding how electrocatalytic materials behave under high‐temperature conditions is an absolute necessity to push these technologies forward. Operando spectroscopic investigations, such as near‐ambient pressure X‐ray photoelectron spectroscopy (NAP–XPS), offer insights into the chemical nature of active working electrodes, including the dynamic response of redox states and adsorbate chemistry to changing electrochemical conditions. Mixed ceramic–metallic electrodes exhibit a limited region with electrochemically active triple‐phase‐boundary (TPB) sites, which are located close to the electrolyte/electrode interface. To monitor this specific region spectroscopically, metallic (Ni) and bimetallic (NiCu) network‐like structures are synthesized on a yttria‐stabilized zirconia electrolyte and the electrochemical state and performance are studied by using operando NAP–XPS. In the experiments, the surface oxidation states under different polarizations are revealed, the gas composition dependent Nernst shift is confirmed, electrocatalytic activities are unraveled, and hydrogen evolution is correlated with the applied potential. The findings demonstrate, the effectiveness of thin‐film model cells with spectroscopically accessible TPB regions for probing interfacial states and electrochemical processes. The obtained fundamental knowledge can provide valuable insights for the advancement of renewable energy storage technologies.

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Combined UHV/high-pressure catalysis setup for depth-resolved near-surface spectroscopic characterization and catalytic testing of model catalysts

Cited by 16 publications

References 28 publications

Boosting Hydrogen Production from Methanol and Water by in situ Activation of Bimetallic Cu−Zr Species

Boosting Hydrogen Production from Methanol and Water by in situ Activation of Bimetallic Cu−Zr Species

A Comparative Discussion of the Catalytic Activity and CO2-Selectivity of Cu-Zr and Pd-Zr (Intermetallic) Compounds in Methanol Steam Reforming

Preparation of Ni and NiCu/Yttria‐Stabilized Zirconia Model Electrodes with Optimized Triple‐Phase Boundary Geometry for Fundamental Operando Spectroscopic Studies

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