Dip-and-pull ambient pressure photoelectron spectroscopy as a spectroelectrochemistry tool for probing molecular redox processes

Temperton, Robert H.; Kawde, Anurag; Eriksson, Axl; Wang, Weijia; Kokkonen, Esko; Jones, Rosemary; Gericke, Sabrina M.; Zhu, Suyun; Quevedo, Wilson; Seidel, Robert; Schnadt, Joachim; Shavorskiy, Andrey; Persson, Petter; Uhlig, Jens

doi:10.1063/5.0130222

Cited by 6 publications

(6 citation statements)

References 31 publications

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“…Dip-and-pull AP-XPS experiments were recently implemented at numerous synchrotrons, for example at the ALS, , SLS, MAX-IV , and BESSY-II . In such experiments, a three-electrode system with the electrolyte and a beaker is placed in the sample chamber of the AP-XPS spectrometer.…”

Section: Resultsmentioning

confidence: 99%

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Understanding Anomalous Gas-Phase Peak Shifts in Dip-and-Pull Ambient Pressure XPS Experiments

Teschner,

Plescher,

Piccinin

et al. 2024

J. Phys. Chem. C

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Dip-and-pull ambient pressure X-ray photoelectron spectroscopy (AP-XPS) holds promise to uncover elementary processes of (photo)electrochemistry. We show, however, that the sample for such experiments should preferably be nonporous and the potential on the surface homogeneous. We carried out dip-andpull AP-XPS experiments on a hematite thin film sample under the photoelectrochemical oxygen evolution reaction (OER) and find unexpected O 1s core level shifts. Upon electrochemical biasing under simulated solar light illumination, the gas-phase water peak shifted more than the electrolyte peak. To uncover the origin of the unexpected larger shift of the gas-phase peak, we performed electrostatic simulations using COMSOL, to map the potential field in the relevant volume between the sample and the first aperture of the XPS spectrometer. A number of geometric models were considered. We find that when the potential on the sample surface is inhomogeneous, e.g., with ionically isolated electrolyte patches, the gas-phase peak of the spectrum can shift more than the peak due to the electrolyte film. This suggests that at the measured sample position, the local potential was not as set by the potentiostat. Despite this, we find reversible consumption and replenishment of hydroxide in the spectra, which, due to OH − being the reactant of the OER in alkaline electrolyte, makes sense chemically. We propose that this is linked to OH − diffusion across the measured sample position, driven by the potential dependent consumption and replenishment of OH − at the nearby well-connected surface regions.

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Section: Resultsmentioning

confidence: 99%

“…Dip-and-pull AP-XPS experiments were carried out at the MAX IV Laboratory using the electrochemical/liquid cell as the sample chamber at the HIPPIE beamline. , A fixed excitation energy of 1600 eV was used in this work. The beamline during the experiments had an energy offset of approximately −1.3 eV at this photon energy.…”

Section: Methodsmentioning

confidence: 99%

Understanding Anomalous Gas-Phase Peak Shifts in Dip-and-Pull Ambient Pressure XPS Experiments

Teschner,

Plescher,

Piccinin

et al. 2024

J. Phys. Chem. C

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“…A special case of an AP-PE technique is the dip-and-pull technique, − where a thin liquid film is prepared by pulling up an electrode from a (degassed) solution beaker within a “vacuum” chamber and stabilized under equilibrated water vapor pressure (∼10 mbar at 10 °C). Films inevitably exhibit a thickness gradient as a function of distance from the solution reservoir. − A potential drawback of this technique is that the electrolyte films are still too thin for carrying out practical electrochemical experiments. One concern is that in the case where chemical reactions involve solutes within the thin solution film, solute replenishing would require long diffusion times from the reservoir to the meniscus films.…”

Section: Introductionmentioning

confidence: 99%

“…A special case of an AP-PE technique is the dip-and-pull technique, 16 − 18 where a thin liquid film is prepared by pulling up an electrode from a (degassed) solution beaker within a “vacuum” chamber and stabilized under equilibrated water vapor pressure (∼10 mbar at 10 °C). Films inevitably exhibit a thickness gradient as a function of distance from the solution reservoir.…”

Section: Introductionmentioning

confidence: 99%

The Metal-Oxide Nanoparticle–Aqueous Solution Interface Studied by Liquid-Microjet Photoemission

2023

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Metrics & MoreArticle Recommendations * sı Supporting Information CONSPECTUS: The liquid-microjet technique combined with soft X-ray photoelectron spectroscopy (PES) has become an exceptionally powerful experimental tool to investigate the electronic structure of liquid water and nonaqueous solvents and solutes, including nanoparticle (NP) suspensions, since its first implementation at the BESSY II synchrotron radiation facility 20 years ago. This Account focuses on NPs dispersed in water, offering a unique opportunity to access the solid−electrolyte interface for identifying interfacial species by their characteristic photoelectron spectral fingerprints. Generally, the applicability of PES to a solid−water interface is hampered due to the small mean free path of the photoelectrons in solution. Several approaches have been developed for the electrode− water system and will be reviewed briefly. The situation is different for the NP−water system. Our experiments imply that the transition-metal oxide (TMO) NPs used in our studies reside close enough to the solution−vacuum interface that electrons emitted from the NP−solution interface (and from the NP interior) can be detected.We were specifically exploring aqueous-phase TMO NPs that have a high potential for (photo)electrocatalytic applications, e.g., for solar fuel generation. The central question we address here is how H 2 O molecules interact with the respective TMO NP surface. Liquid-microjet PES experiments, performed from hematite (α-Fe 2 O 3 , iron(III) oxide) and anatase (TiO 2 , titanium(IV) oxide) NPs dispersed in aqueous solutions, exhibit sufficient sensitity to distinguish between free bulk-solution water molecules and those adsorbed at the NP surface. Moreover, hydroxyl species resulting from dissociative water adsorption can be identified in the photoemission spectra. An important aspect is that in the NP(aq) system the TMO surface is in contact with a true extended bulk electrolyte solution rather than with a few monolayers of water, as is the case in experiments using single-crystal samples. This has a decisive effect on the interfacial processes that can occur since NP−water interactions can be uniquely investigated as a function of pH and provides an environment allowing for unhindered proton migration. Our studies confirm that water is dissociatively adsorbed at the hematite surface and molecularly adsorbed at the TiO 2 NP surface at low pH. In contrast, at near-basic pH the water interaction is dissociative at the TiO 2 NP surface.The liquid-microjet measurements presented here also highlight the multiple aspects of photoemission necessary for a full characterization of TMO nanoparticle surfaces in aqueous environments. For instance, we exploit the ability to increase speciesspecific electron signals via resonant photoemission, so-called partial electron yield X-ray absorption (PEY-XA) spectra, and from valence photoelectron and resonant Auger-electron spectra. We also address the potential of these resonance processes and the associated ultraf...

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“…The development of operando measuring conditions for analytical techniques, as in the case of ambient pressure X-ray photoelectron spectroscopy (AP-XPS), has enabled a more fundamental understanding of interfacial phenomena because they enable the interrogation of the material under operating conditions. − This is of paramount importance to the field of PEC water electrolysis as the band structure of a photocatalytic, semiconducting material in contact with an electrolyte (biased and not) is not the same as that in vacuum. The space charge region (SCR) forming (depletion region for an n-type semiconductor) under equilibrium conditions in the solid/liquid junction is a key factor for the transport of photogenerated holes from the solid to the surface of the photoanode electrode.…”

Section: Introductionmentioning

confidence: 99%

Interrogation of the Interfacial Energetics at a Tantalum Nitride/Electrolyte Heterojunction during Photoelectrochemical Water Splitting by Operando Ambient Pressure X-ray Photoelectron Spectroscopy

Dahl,

Sunding,

Killi

et al. 2023

ACS Catal.

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Photoelectrochemical (PEC) water electrolysis is an important energy conversion (power-to-chemical) method, providing a solution to the intermittent nature of solar energy. However, as PEC systems usually suffer from low operational stability, they are seriously lagging in up-scaled demonstrations and viability. PEC systems are based on semiconductor/liquid interfaces, which have been extensively studied by experiments and theory, but there is a significant knowledge gap in the energetics of such interfaces during operation. In this work, operando ambient pressure X-ray photoelectron spectroscopy (AP-XPS) has been used to characterize the electrical and spectroscopic properties of a pristine Ta 3 N 5 photoelectrode and a Ta 3 N 5 /NiO x protection/passivation layer system, which stabilizes an otherwise quickly corroding pristine photoelectrode. We directly observed Fermi-level pinning of Ta 3 N 5 within the applied potential window under both dark and illumination conditions, detrimental to the performance and stability of the photoelectrode. Interestingly, in the Ta 3 N 5 /NiO x protection/passivation layer system, the Fermi level gets unpinned under illumination, allowing quasi-Fermi-level splitting and sustaining a significant PEC performance as well as high stability.

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Dip-and-pull ambient pressure photoelectron spectroscopy as a spectroelectrochemistry tool for probing molecular redox processes

Cited by 6 publications

References 31 publications

Understanding Anomalous Gas-Phase Peak Shifts in Dip-and-Pull Ambient Pressure XPS Experiments

Understanding Anomalous Gas-Phase Peak Shifts in Dip-and-Pull Ambient Pressure XPS Experiments

The Metal-Oxide Nanoparticle–Aqueous Solution Interface Studied by Liquid-Microjet Photoemission

Interrogation of the Interfacial Energetics at a Tantalum Nitride/Electrolyte Heterojunction during Photoelectrochemical Water Splitting by Operando Ambient Pressure X-ray Photoelectron Spectroscopy

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