| 1. |
- Zeller, Patrick, et al.
(författare)
-
Scanning Photoelectron Spectro-Microscopy : A Modern Tool for the Study of Materials at the Nanoscale
- 2018
-
Ingår i: Physica Status Solidi (A) Applications and Materials Science. - : Wiley. - 1862-6300. ; 215:19
-
Tidskriftsartikel (refereegranskat)abstract
- The advanced properties of modern materials originate from their nanoscale size and shape and from chemical modifications or doping. Special techniques that can measure the chemical state in the nanoscale are required for exploration and understanding the properties of these materials. While X-ray photoelectron spectroscopy (XPS) can access the necessary chemical information, conventional setups have no spatial resolution. The scanning photoelectron microscope (SPEM) takes in advent the third generation synchrotron radiation facilities and uses a zone plate (ZP) focusing optics that allows spatially resolved XPS measurements in the submicron scale. Several recent examples of investigations of chemically modified or doped nanomaterials are given. The modification of suspended and supported graphene with nitrogen and fluorine is presented as well as the doping dependent position of the Fermi-level in single GsAs nanowires and the Mott–Hubbard transition in Cr-doped vanadium oxide. These examples show several peculiar SPEM abilities like a high surface and chemical sensitivity and a submicron spatial resolution proving the capability and importance of this technique to study materials at the nanoscale.
|
|
| 2. |
- Amati, Matteo, et al.
(författare)
-
Near ambient pressure photoelectron spectro-microscopy : From gas-solid interface to operando devices
- 2021
-
Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 54:20
-
Tidskriftsartikel (refereegranskat)abstract
- Near ambient pressure scanning photoelectron microscopy adds to the widely used photoemission spectroscopy and its chemically selective capability two key features: (1) the possibility to chemically analyse samples in a more realistic gas pressure condition and (2) the capability to investigate a system at the relevant spatial scale. To achieve these goals the approach developed at the ESCA Microscopy beamline at the Elettra Synchrotron facility combines the submicron lateral resolution of a Scanning Photoelectron Microscope with a custom designed Near Ambient Pressure Cell where a gas pressure up to 0.1 mbar can be achieved. In this manuscript a review of experiments performed with this unique setup will be presented to illustrate its potentiality in both fundamental and applicative research such as the oxidation reactivity and gas sensitivity of metal oxides and semiconductors. In particular, the capability to perform operando experiments with this setup opens the possibility to study operating devices and to properly address the real nature of the studied systems, because if microscopy and spectroscopy are simultaneously combined in a single technique it can yield to more conclusive results.
|
|
| 3. |
- Amati, M., et al.
(författare)
-
Scanning photoelectron spectromicroscopy : From static to operando studies of functional materials
- 2023
-
Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048. ; 265
-
Tidskriftsartikel (refereegranskat)abstract
- The scanning photoelectron microscope (SPEM), developed more than 30 years ago, has undergone numerous technical developments, providing an incredibly vast kind of feasible sample environments, which span from the traditional high spatial resolution core level based chemical analysis to insitu and operando complex experiments, including also electrochemical setups and operational electronic devices at various temperatures. Another important step ahead is overcoming the so-called pressure gap for operando studies, recently extended to near ambient values by building special environmental cells. Using recent results of conventional and unconventional experiments, obtained with SPEM at the ESCA Microscopy beamline at Elettra Sincrotrone Trieste the present review demonstrates the current potential of this type of photoelectron spectromicroscopy to explore the interfacial properties of functional materials with high spatial resolution.
|
|
| 4. |
- Armillotta, Francesco, et al.
(författare)
-
Single Metal Atom Catalysts and ORR : H-Bonding, Solvation, and the Elusive Hydroperoxyl Intermediate
- 2022
-
Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 12:13, s. 7950-7959
-
Tidskriftsartikel (refereegranskat)abstract
- The widely investigated oxygen reduction reaction (ORR) is well-known to proceed via two competing routes, involving two or four electrons, and yielding different reaction products, respectively. Both pathways are believed to share a common, elusive intermediate, namely, the hydroperoxyl radical. By exploiting a cobalt single-atom biomimetic model catalyst, based on a self-assembled monolayer of Co-porphyrins grown on an almost free-standing graphene sheet, we identify, in situ at room temperature in O2+H2O atmosphere, a hydroperoxyl-water cluster that is stabilized at the Co single-metal atom catalytic site. We show that the interplay between charge transfer, dipole and H-bonding, and water solvation behavior actually determines the hydroperoxyl-water complex stability, the Co-OOH bonding geometry, and, prospectively, opens to the engineered control of the selectivity of ORR pathways.
|
|
| 5. |
- Biasin, Pietro, et al.
(författare)
-
From borophene polymorphs towards a single honeycomb borophane phase : reduction of hexagonal boron layers on Al(111)
- 2023
-
Ingår i: Nanoscale. - 2040-3364. ; 15:45, s. 18407-18414
-
Tidskriftsartikel (refereegranskat)abstract
- The recent interest in characterizing 2D boron polymorphs has led to claims of the first stabilization of a honeycomb phase with conical Dirac-like electron dispersion. However, the synthesis of chemically stable, single, and homogeneous 2D boron phases still represents a significant experimental challenge. This is ascribed to the intrinsic boron electronic configuration that, at variance with carbon, leads to the formation of multi-center covalent bonds. External charge compensation by substrate-induced doping can steer the geometry of the layer, both in the buckling and in the density of B vacancies, like in the case of the recently achieved stabilization of honeycomb boron layers on Al(111). The price to pay is however a strong boron-support interaction, resulting in general in a limiting kinetic hindrance with respect to the synthesis of homogenous single phases. In the specific case of Al(111) an AlB2 layer is known to form at the surface, quite far from a desirable quasi-freestanding borophene monolayer and at variance with graphene, which can be easily synthesized in an almost freestanding configuration e.g. on Ir(111). We provide here evidence for the (reversible) formation of well-ordered honeycomb borophane upon hydrogenation of the honeycomb boron phase on Al(111).
|
|
| 6. |
- Biasin, Pietro, et al.
(författare)
-
Growth and Redox Properties of Boron on Al(111) : Competing Affinities in the Case of Honeycomb AlB2
-
Ingår i: ACS Nano. - 1936-0851.
-
Tidskriftsartikel (refereegranskat)abstract
- The complexity of the geometric and electronic structure of boron allotropes is associated with the multicentric bonding character and the consequent B polymorphism. When growth is limited to two-dimensions (2D), the structural and electronic confinement yields the borophenes family, where the interaction with the templating substrate actually determines the stability of inequivalent boron phases. We report here a detailed study of the growth of the honeycomb AlB2 phase on Al(111), followed by an investigation of its oxidation and reduction properties. By means of a combined experimental and theoretical approach, we show that the structure of the B/Al interface is affected by the complex interplay between B, Al, and common reactive agents like oxygen and hydrogen. While kinetic effects associated with diffusion and strain release influence the AlB2 growth in vacuo, Al, B, O, and H chemical affinities determine its redox behavior. Reduction with atomic hydrogen involves the B layer and yields an ordered honeycomb borophane H/AlB2 phase. Instead, oxidation takes place at the Al interface, giving origin to buried and 1D surface aluminum oxide phases.
|
|
| 7. |
- Boix, Virginia, et al.
(författare)
-
Following the Kinetics of Undercover Catalysis with APXPS and the Role of Hydrogen as an Intercalation Promoter
- 2022
-
Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 12:16, s. 9897-9907
-
Tidskriftsartikel (refereegranskat)abstract
- While improved catalytic properties of many surfaces covered by two-dimensional materials have been demonstrated, a detailed in situ picture of gas delivery, undercover reaction, and product removal from the confined space is lacking. Here, we demonstrate how a combination of gas pulses with varying compositions and time-resolved ambient pressure photoelectron spectroscopy can be used to obtain such knowledge. This approach allows us to sequentially form and remove undercover reaction products, in contrast to previous work, where co-dosing of reactant gases was used. In more detail, we study CO and H2 oxidation below oxygen-intercalated graphene flakes partially covering an Ir(111) surface. We show that hydrogen rapidly mixes into a p(2 × 1)-O structure below the graphene flakes and converts it into a dense OH-H2O phase. In contrast, CO exposure only leads to oxygen removal from the confined space and little CO intercalation. Finally, our study shows that H2 mixed into CO pulses can be used as a promoter to change the undercover chemistry. Their combined exposure leads to the formation of OH-H2O below the flakes, which, in turn, unbinds the flakes for enough time for CO to intercalate, resulting in a CO structure stable only in coexistence with the OH-H2O phase. Altogether, our study proves that promoter chemistry in the form of adding trace gases to the gas feed is essential to consider for undercover reactions.
|
|
| 8. |
- Boix, Virginia, et al.
(författare)
-
Graphene as an Adsorption Template for Studying Double Bond Activation in Catalysis
- 2022
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:33, s. 14116-14124
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrogenated graphene (H-Gr) is an extensively studied system not only because of its capabilities as a simplified model system for hydrocarbon chemistry but also because hydrogenation is a compelling method for Gr functionalization. However, knowledge of how H-Gr interacts with molecules at higher pressures and ambient conditions is lacking. Here we present experimental and theoretical evidence that room temperature O2exposure at millibar pressures leads to preferential removal of H dimers on H-functionalized graphene, leaving H clusters on the surface. Our density functional theory (DFT) analysis shows that the removal of H dimers is the result of water or hydrogen peroxide formation. For water formation, we show that the two H atoms in the dimer motif attack one end of the physisorbed O2molecule. Moreover, by comparing the reaction pathways in a vacuum with the ones on free-standing graphene and on the graphene/Ir(111) system, we find that the main role of graphene is to arrange the H atoms in geometrical positions, which facilitates the activation of the O═O double bond.
|
|
| 9. |
- Cole, Jordan, et al.
(författare)
-
In situ XPS of competitive CO2/H2O absorption in an ionic liquid
- 2023
-
Ingår i: JPhys Materials. - 2515-7639. ; 6:4
-
Tidskriftsartikel (refereegranskat)abstract
- Superbasic ionic liquids (SBILs) are being investigated as potential carbon dioxide (CO2) gas capture agents, however, the presence of H2O in the flue stream can inhibit the uptake of CO2. In this study a thin film of the SBIL trihexyltetradecylphosphonium 1,2,4-triazolide ([P66614][124Triz]) was deposited onto rutile TiO2 (110) using in situ electrospray deposition and studied upon exposure to CO2 and H2O using in situ near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS). The molar uptake ratio of gas in the electrosprayed SBIL (n gas :n IL) was calculated to be 0.3:1 for CO2, 0.7:1 for H2O, and 0.9:1 for a CO2/H2O mixture. NAP-XPS taken at two different depths reveals that the competitive absorption of CO2 and H2O in [P66614][124Triz] varies with sampling depth. A greater concentration of CO2 absorbs in the bulk layers, while more H2O adsorbs/absorbs at the surface. The presence of H2O in the gas mixture does not inhibit the absorption of CO2. Measurements taken during exposure and after the removal of gas indicate that CO2 absorbed in the bulk does so reversibly, whilst CO2 adsorbed/absorbed at the surface does so irreversibly. This is contrary to the fully reversible CO2 reaction shown for bulk ionic liquids (ILs) in literature and suggests that irreversible absorption of CO2 in our highly-structured thin films is largely attributed to reactions at the surface. This has potential implications on IL gas capture and thin film IL catalysis applications.
|
|
| 10. |
- Gericke, Sabrina Maria, et al.
(författare)
-
In Situ H2 Reduction of Al2O3-Supported Ni- and Mo-Based Catalysts
- 2022
-
Ingår i: Catalysts. - : MDPI. - 2073-4344. ; 12:7
-
Tidskriftsartikel (refereegranskat)abstract
- Nickel (Ni)-promoted Molybdenum (Mo)-based catalysts are used for hydrotreatment processes in the chemical industry where the catalysts are exposed to high-pressure H2 at elevated temperature. In this environment, the catalyst transforms into the active phase, which involves the reduction of the oxide. Here, we report on the first in situ study on the reduction of alumina supported Ni- and Mo-based catalysts in 1 mbar H2 using ambient-pressure X-ray photoelectron spectroscopy (APXPS). The study confirms that mixing Ni and Mo lowers the reduction temperature of both Ni- and Mo-oxide as compared to the monometallic catalysts and shows that the MoO3 reduction starts at a lower temperature than the reduction of NiO in NiMo/Al2O3 catalysts. Additionally, the reduction of Ni and Mo foil was directly compared to the reduction of the Al2O3-supported catalysts and it was observed that the reduction of the supported catalysts is more gradual than the reduction of the foils, indicating a strong interaction between the Ni/Mo and the alumina support. © 2022 by the authors.
|
|
| 11. |
- Knudsen, Jan, et al.
(författare)
-
Stroboscopic operando spectroscopy of the dynamics in heterogeneous catalysis by event-averaging
- 2021
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- Heterogeneous catalyst surfaces are dynamic entities that respond rapidly to changes in their local gas environment, and the dynamics of the response is a decisive factor for the catalysts’ action and activity. Few probes are able to map catalyst structure and local gas environment simultaneously under reaction conditions at the timescales of the dynamic changes. Here we use the CO oxidation reaction and a Pd(100) model catalyst to demonstrate how such studies can be performed by time-resolved ambient pressure photoelectron spectroscopy. Central elements of the method are cyclic gas pulsing and software-based event-averaging by image recognition of spectral features. A key finding is that at 3.2 mbar total pressure a metallic, predominantly CO-covered metallic surface turns highly active for a few seconds once the O2:CO ratio becomes high enough to lift the CO poisoning effect before mass transport limitations triggers formation of a √5 oxide.
|
|
| 12. |
- Larsson, Alfred, et al.
(författare)
-
In situ quantitative analysis of electrochemical oxide film development on metal surfaces using ambient pressure X-ray photoelectron spectroscopy : Industrial alloys
- 2023
-
Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 611
-
Tidskriftsartikel (refereegranskat)abstract
- Ambient Pressure X-ray Photoelectron Spectroscopy combined with an electrochemical setup is used to study, in situ, the electrochemical oxide growth on an in-dustrial Ni-Cr-Mo alloy. The native oxide film was characterized in vacuum and in water vapor at 17 mbar, and was found to be 11.4 & ANGS; thick and rich in Cr3+. In 0.1 M NaCl electrolyte, anodic growth of the oxide film at potentials up to 700 mV vs Ag/AgCl nearly doubled the thickness of the oxide film. Moreover, a transformation of the oxide composition occurred, as the oxide became enriched in Mo6+ with a chemical fingerprint more like that of pure MoO3. Both thermodynamics and kinetics of the oxidation of the alloying elements dictate the oxide film growth and composition. Furthermore, we develop the quantitative analysis of oxide composition and thickness to take into account the attenuation through the liquid water and the water vapor atmosphere. Finally, we discuss the differences between ex situ, UHV, in situ, and operando measurements. Our approach is robust, fast, simple, and suitable for systematically probing metal surfaces after aqueous exposure and electro-chemical polarization, which promises wide applications for studies of solid-liquid interfaces in corrosion, batteries, fuel cells, and electrocatalysis.
|
|
| 13. |
- Larsson, Alfred, et al.
(författare)
-
The Oxygen Evolution Reaction Drives Passivity Breakdown for Ni–Cr–Mo Alloys
- 2023
-
Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 35:39
-
Tidskriftsartikel (refereegranskat)abstract
- Corrosion is the main factor limiting the lifetime of metallic materials, and a fundamental understanding of the governing mechanism and surface processes is difficult to achieve since the thin oxide films at the metal–liquid interface governing passivity are notoriously challenging to study. In this work, a combination of synchrotron-based techniques and electrochemical methods is used to investigate the passive film breakdown of a Ni–Cr–Mo alloy, which is used in many industrial applications. This alloy is found to be active toward oxygen evolution reaction (OER), and the OER onset coincides with the loss of passivity and severe metal dissolution. The OER mechanism involves the oxidation of Mo4+ sites in the oxide film to Mo6+ that can be dissolved, which results in passivity breakdown. This is fundamentally different from typical transpassive breakdown of Cr-containing alloys where Cr6+ is postulated to be dissolved at high anodic potentials, which is not observed here. At high current densities, OER also leads to acidification of the solution near the surface, further triggering metal dissolution. The OER plays an important role in the mechanism of passivity breakdown of Ni–Cr–Mo alloys due to their catalytic activity, and this effect needs to be considered when studying the corrosion of catalytically active alloys.
|
|
| 14. |
- Scardamaglia, Mattia, et al.
(författare)
-
Comparative study of copper oxidation protection with graphene and hexagonal boron nitride
- 2021
-
Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 171, s. 610-617
-
Tidskriftsartikel (refereegranskat)abstract
- The use of protective barriers to isolate a metal surface from an aggressive environment is a common way to inhibit its degradation. We used ambient pressure x-ray photoelectron spectroscopy to assess in real time the evolution of the copper surface and the contextual protective action of 2D material coatings (graphene and hexagonal boron nitride) towards copper oxidation. In an isobaric experiment with 2 mbar of oxygen, the bare copper oxidizes near room temperature, while both 2D materials can retard the onset temperature for the first oxidation of copper by more than 120 °C. However, their protection mechanism is different: boron nitride behaves more straightforwardly, forming an effective barrier to copper oxidation until it is etched away at high temperatures, leading to a rapid oxidation to cuprous and then cupric oxide. On the other hand, graphene reveals to be a more interesting playground underneath oxygen intercalates and begins a slower undercover oxidation of copper. The coexistence between graphene and cuprous oxide, not observed in boron nitride, protects the copper from further oxidation to cupric oxide.
|
|
| 15. |
- Scardamaglia, Mattia, et al.
(författare)
-
Depth distribution of alkali metal ions on supported graphene in the presence of water
- 2023
-
Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 262
-
Tidskriftsartikel (refereegranskat)abstract
- The interaction of alkali ions with multilayer graphene is critical in many applications, for example in energy storage devices. This requires a detailed understanding of ion interactions with carbonaceous layers. The mechanism of ion intercalation into graphene can be different from that observed for hard graphite. In this paper, we present an investigation of the vertical alkali ion (Na, K, Cs) distribution on multilayer graphene deposited onto SiO2 in vacuum and in the presence of water vapor using Standing Wave Ambient Pressure Photoemission Spectroscopy. It was found that Cs, K, and Na ions do not intercalate into multilayer graphene under vacuum conditions. The most likely reasons for this behavior are the reversibility of the process due to large inter-sheet spacing or lack of time for intercalation. When exposed to water vapor, Na ions intercalate soft carbon whereas Cs ions do not. This is a clear indication for the difference in the intercalation mechanisms on hard graphite and soft graphene.
|
|
| 16. |
- Scardamaglia, Mattia, et al.
(författare)
-
Graphene-Based Metal-Free Catalysis
- 2019
-
Ingår i: NATO Science for Peace and Security Series A : Chemistry and Biology - Chemistry and Biology. - Dordrecht : Springer Netherlands. - 1874-6489. - 9789402416190 - 9789402416206 ; , s. 173-200
-
Bokkapitel (refereegranskat)abstract
- This chapter focuses on the use of doped carbon nanomaterials in catalysis. The availability of carbon nanotubes in the ‘90s and graphene about 10Â years later, prompted the development of fundamental research and novel nanotechnologies. We discuss this topic from a point of view that links fundamental surface science to the field of catalysis, in order to present the state of the art. We describe scientific questions that material scientists have faced during these last decades, in particular, we concentrate on the debate over the role that the different nitrogen configurations in the graphene lattice can play in certain catalytic processes.
|
|
| 17. |
- Scardamaglia, Mattia, et al.
(författare)
-
Highlighting the Dynamics of Graphene Protection toward the Oxidation of Copper under Operando Conditions
- 2019
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 11:32, s. 29448-29457
-
Tidskriftsartikel (refereegranskat)abstract
- We performed spatially resolved near-ambient-pressure photoemission spectromicroscopy on graphene-coated copper in operando under oxidation conditions in an oxygen atmosphere (0.1 mbar). We investigated regions with bare copper and areas covered with mono- and bi-layer graphene flakes, in isobaric and isothermal experiments. The key method in this work is the combination of spatial and chemical resolution of the scanning photoemission microscope operating in a near-ambient-pressure environment, thus allowing us to overcome both the material and pressure gap typical of standard ultrahigh-vacuum X-ray photoelectron spectroscopy (XPS) and to observe in operando the protection mechanism of graphene toward copper oxidation. The ability to perform spatially resolved XPS and imaging at high pressure allows for the first time a unique characterization of the oxidation phenomenon by means of photoelectron spectromicroscopy, pushing the limits of this technique from fundamental studies to real materials under working conditions. Although bare Cu oxidizes naturally at room temperature, our results demonstrate that such a graphene coating acts as an effective barrier to prevent copper oxidation at high temperatures (over 300 °C), until oxygen intercalation beneath graphene starts from boundaries and defects. We also show that bilayer flakes can protect at even higher temperatures. The protected metallic substrate, therefore, does not suffer corrosion, preserving its metallic characteristic, making this coating appealing for any application in an aggressive atmospheric environment at high temperatures.
|
|
| 18. |
- Shavorskiy, Andrey, et al.
(författare)
-
Gas Pulse-X-Ray Probe Ambient Pressure Photoelectron Spectroscopy with Submillisecond Time Resolution
- 2021
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:40, s. 47629-47641
-
Tidskriftsartikel (refereegranskat)abstract
- A setup capable of conducting gas pulse-X-ray probe ambient pressure photoelectron spectroscopy with high time resolution is presented. The setup makes use of a fast valve that creates gas pulses with an internal pressure in the mbar range and a rising edge of few hundreds of microseconds. A gated detector based on a fast camera is synchronized with the valve operation to measure X-ray photoemission spectra with up to 20 μs time resolution. The setup is characterized in several experiments in which the N2 gas is pulsed either into vacuum or a constant flow of another gas. The observed width of the pulse rising edge is 80 μs, and the maximum internal pulse pressure is ∼1 mbar. The CO oxidation reaction over Pt (111) was used to demonstrate the capability of the setup to correlate the gas phase composition with that of the surface during transient supply of CO gas into an O2 stream. Thus, formation of both chemisorbed and oxide oxygen species was observed prior to CO gas perturbation. Also, the data indicated that both the Langmuir-Hinshelwood and Mars-van-Krevelen mechanisms play an important role in the oxidation of carbon monoxide under ambient conditions.
|
|
| 19. |
|
|
| 20. |
- Yue, Xiaoqi, et al.
(författare)
-
In depth analysis of the passive film on martensitic tool alloy: Effect of tempering temperature
- 2024
-
Ingår i: Corrosion Science. - : Elsevier. - 0010-938X .- 1879-0496. ; 234
-
Tidskriftsartikel (refereegranskat)abstract
- Effect of tempering temperature on the composition of the passive film of a martensitic tool alloy was studied by synchrotron-based hard/soft X-ray photoelectron spectroscopy and electrochemical analyses. The contents of Cr and Mo in the passive film are affected by precipitation of tempering carbides. Increase of tempering temperature from 200 to 525°C leads to enhanced formation of Cr/Mo-rich tempering carbides and Cr depletion. Tempering at 525°C results in a Cr content < 11 at% in the underlying metallic layer and formation of a Cr-deficient defective passive film, and thus loss of passivity for the tool alloy in corrosive conditions.
|
|
| 21. |
- Yue, Xiaoqi, et al.
(författare)
-
Synchrotron-based near ambient-pressure X-ray photoelectron spectroscopy and electrochemical studies of passivation behavior of N- and V-containing martensitic stainless steel
- 2023
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 214, s. 111018-
-
Tidskriftsartikel (refereegranskat)abstract
- Passivation behavior of a N-and V-containing martensite stainless steel was studied by synchrotron-based near ambient-pressure X-ray photoelectron spectroscopy, electrochemical analyses, and thermodynamic calculation. The passive film consists of Cr3+, Fe(2, 3)+, and V(2, 3, 4)+ oxides as inner layer, and Cr3+ and Fe3+ hydroxides as outer layer. Austenitization at 1080 oC (rather than 1010 oC) and anodic polarization facilitate transformation of CrN to Cr2O3 leading to further enrichment of Cr3+ oxide in the passive film. Whereas higher Cl- concentration promotes film dissolution leading to higher level of point defects and higher fraction of remaining V oxides in the passive film.
|
|
| 22. |
- Zhu, Suyun, et al.
(författare)
-
HIPPIE : a new platform for ambient-pressure X-ray photoelectron spectroscopy at the MAX IV Laboratory
- 2021
-
Ingår i: Journal of Synchrotron Radiation. - : INT UNION CRYSTALLOGRAPHY. - 1600-5775 .- 0909-0495. ; 28, s. 624-636
-
Tidskriftsartikel (refereegranskat)abstract
- HIPPIE is a soft X-ray beamline on the 3 GeV electron storage ring of the MAX IV Laboratory, equipped with a novel ambient-pressure X-ray photoelectron spectroscopy (APXPS) instrument. The endstation is dedicated to performing in situ and operando X-ray photoelectron spectroscopy experiments in the presence of a controlled gaseous atmosphere at pressures up to 30 mbar [1 mbar = 100 Pa] as well as under ultra-high-vacuum conditions. The photon energy range is 250 to 2200 eV in planar polarization and with photon fluxes >1012 photons s-1 (500 mA ring current) at a resolving power of greater than 10000 and up to a maximum of 32000. The endstation currently provides two sample environments: a catalysis cell and an electrochemical/liquid cell. The former allows APXPS measurements of solid samples in the presence of a gaseous atmosphere (with a mixture of up to eight gases and a vapour of a liquid) and simultaneous analysis of the inlet/outlet gas composition by online mass spectrometry. The latter is a more versatile setup primarily designed for APXPS at the solid-liquid (dip-and-pull setup) or liquid-gas (liquid microjet) interfaces under full electrochemical control, and it can also be used as an open port for ad hoc-designed non-standard APXPS experiments with different sample environments. The catalysis cell can be further equipped with an IR reflection-absorption spectrometer, allowing for simultaneous APXPS and IR spectroscopy of the samples. The endstation is set up to easily accommodate further sample environments.
|
|
| 23. |
- Zou, Zhiyu, et al.
(författare)
-
In Situ Observation of C−C Coupling and Step Poisoning During the Growth of Hydrocarbon Chains on Ni(111)
- 2023
-
Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 62:1
-
Tidskriftsartikel (refereegranskat)abstract
- The synthesis of high-value fuels and plastics starting from small hydrocarbon molecules plays a central role in the current transition towards renewable energy. However, the detailed mechanisms driving the growth of hydrocarbon chains remain to a large extent unknown. Here we investigated the formation of hydrocarbon chains resulting from acetylene polymerization on a Ni(111) model catalyst surface. Exploiting X-ray photoelectron spectroscopy up to near-ambient pressures, the intermediate species and reaction products have been identified. Complementary in situ scanning tunneling microscopy observations shed light onto the C−C coupling mechanism. While the step edges of the metal catalyst are commonly assumed to be the active sites for the C−C coupling, we showed that the polymerization occurs instead on the flat terraces of the metallic surface.
|
|
