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Probing intermediate configurations of oxygen evolution catalysis across the light spectrum

Anonymous — Sun, 15 Sep 2024 21:43:32 +0000

Probing intermediate configurations of oxygen evolution catalysis across the light spectrum Anonymous (not verified) Sun, 09/15/2024 - 15:43

Jin Suntivich, Geoffroy Hautier, Ismaila Dabo, Ethan J. Crumlin, Dhananjay Kumar & Tanja Cuk

Nature Energy (Perspective) 2024 DOI: https://doi.org/10.1038/s41560-024-01583-x

The oxygen evolution reaction is crucial to sustainable electro- and photo-electrochemical approaches to chemical energy production (for example, H₂). Although mechanistic descriptions of the oxygen evolution reaction have been proposed, the frontier challenge is to extract the molecular details of its elementary steps. Here we discuss how advances in spectroscopy and theory are allowing for configurations of reaction intermediates to be elucidated, distinguishing between experimental approaches (static and dynamic) across a range of surface oxygen binding energies on catalysts (from ruthenium to titanium oxides). We outline how interpreting X-ray and optical spectra relies on established and newly implemented computational techniques. A key emphasis is on detecting adsorbed oxygen intermediates at the oxide/water interface by their chemical composition, electronic and vibrational levels and ion–electron kinetic pathways. Integrating the computational advances with the experimental spectra along these lines could ultimately resolve the elementary steps, elucidating how each intermediate leads to another during oxygen evolution reaction.

The oxygen evolution reaction is crucial to sustainable electro- and photo-electrochemical approaches to chemical energy production (for example, H2). Although mechanistic descriptions of the oxygen evolution reaction have been proposed, the frontier challenge is to extract the molecular details of its elementary steps. Here we discuss how advances in spectroscopy and theory are allowing for configurations of reaction intermediates to be elucidated, distinguishing between experimental approaches (static and dynamic) across a range of surface oxygen binding energies on catalysts (from ruthenium to titanium oxides).

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Phenomenology of Intermediate Molecular Dynamics at Metal-Oxide Interfaces

Anonymous — Wed, 31 Jul 2024 14:50:57 +0000

Phenomenology of Intermediate Molecular Dynamics at Metal-Oxide Interfaces Anonymous (not verified) Wed, 07/31/2024 - 08:50

Tanja Cuk

Annual Reviews of Physical Chemistry 2024, 75, 457 DOI: https://www.annualreviews.org/content/journals/10.1146/annurev-physchem-062123-022921

Reaction intermediates buried within a solid-liquid interface are difficult targets for physiochemical measurements. They are inherently molecular and locally dynamic, while their surroundings are extended by a periodic lattice on one side and the solvent dielectric on the other. Challenges compound on a metal-oxide surface of varied sites and especially so at its aqueous interface of many prominent reactions. Recently, phenomenological theory coupled with optical spectroscopy has become a more prominent tool for isolating the intermediates and their molecular dynamics. The following article reviews three examples of the SrTiO3-aqueous interface subject to the oxygen evolution from water: reaction-dependent component analyses of time-resolved intermediates, a Fano resonance of a mode at the metal-oxide–water interface, and reaction isotherms of metastable intermediates. The phenomenology uses parameters to encase what is unknown at a microscopic level to then circumscribe the clear and macroscopically tuned trends seen in the spectroscopic data.

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Ultrafast Electronic and Vibrational Spectroscopy of Electrochemical Transformations on a Metal-Oxide Surface during Oxygen Evolution Catalysis

Anonymous — Thu, 27 Jun 2024 17:39:00 +0000

Ultrafast Electronic and Vibrational Spectroscopy of Electrochemical Transformations on a Metal-Oxide Surface during Oxygen Evolution Catalysis Anonymous (not verified) Thu, 06/27/2024 - 11:39

Tanja Cuk*, Michael Paolino, Suryansh Singh, James Stewart, Xihan Chen, and Ilya Vinogradov

ACS Catalysis 2024, 14, 9901 DOI: https://doi.org/10.1021/acscatal.3c05931

Oxygen evolution catalysis fuels the planet through photosynthesis and is a primary means for hydrogen storage in energy technologies. Yet the detection of intermediates of the oxygen evolution reaction (OER) central to the catalytic mechanism has been an ongoing challenge. This tutorial and minireview covers the relevance of ultrafast electronic and vibrational spectroscopy of the electrochemical transformations of a metal-oxide surface undergoing OER. Here, we highlight the ultrafast trigger and probes of the electron-doped SrTiO₃/electrolyte as the primary example in which light probes across the electromagnetic spectrum have detected intermediate forms. We compare the results to other early transition-metal-oxide surfaces when they exist for select probes and longer timescales. The first part covers how the catalytic reaction is triggered by ultrafast light pulses, describing the semiconducting depletion and electrolyte Helmholtz layers. The second part covers the detection of the intermediates that occur upon electron and proton transfer from an adsorbed water species by transient spectroscopy. Their detection by a broadband visible probe, a mid-infrared evanescent wave, and a coherent acoustic wave respectively targets electronic states, vibrational levels, and lattice strain respectively. One of the aims is a tutorial on how these measurements are made and to what extent they allow for the interpretation of experimental spectra by intermediate configurations predicted by theory. Another aim is to describe what these experiments directly recommend in terms of future efforts to visualize the OER intermediates and their dynamics.

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Formation of the oxyl’s potential energy surface by the spectral kinetics of a vibrational mode

Anonymous — Thu, 02 May 2024 02:49:58 +0000

Formation of the oxyl’s potential energy surface by the spectral kinetics of a vibrational mode Anonymous (not verified) Wed, 05/01/2024 - 20:49

James Stewart^{^}, Paul Zakya^{^}, Christen Courter, and Tanja Cuk*

Journal of Chemical Physics2024 DOI: https://doi.org/10.1063/5.0202441

One of the most reactive intermediates for oxidative reactions is the oxyl radical, an electron-deficient oxygen atom. The discovery of a new vibration upon photoexcitation of the oxygen evolution catalysis detected the oxyl radical at the SrTiO₃ surface. The vibration was assigned to a motion of the sub-surface oxygen underneath the titanium oxyl (Ti–O^●−) created upon hole transfer to (or electron extraction from) a hydroxylated surface site. Evidence for such an interfacial mode is derived from its spectral shape, which exhibited a Fano resonance—a coupling of a sharp normal mode to continuum excitations. Here, this Fano resonance is utilized to derive precise formation kinetics of the oxyl radical and its associated potential energy surface (PES). From the Fano lineshape, the formation kinetics are obtained from the anti-resonance (the kinetics of the coupling factor), the resonance (the kinetics of the coupled continuum excitations), and the frequency integrated spectrum (the kinetics of the normal mode’s cross-section). All three perspectives yield logistic function growth with a half-rise of 2.3 ± 0.3 ps and a time constant of 0.48 ± 0.09 ps. A non-equilibrium transient associated with photoexcitation is separated from the rise of the equilibrated PES. The logistic function characterizes the oxyl coverage at the very initial stages (t ∼ 0) to have an exponential growth rate that quickly decreases toward zero as a limiting coverage is reached. Such time-dependent reaction kinetics identify a dynamic activation barrier associated with the formation of a PES and quantify it for oxyl radical coverage.

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Assessing and Quantifying Thermodynamically Concomitant Degradation during Oxygen Evolution from Water on SrTiO3

Anonymous — Mon, 19 Jun 2023 19:02:51 +0000

Assessing and Quantifying Thermodynamically Concomitant Degradation during Oxygen Evolution from Water on SrTiO3 Anonymous (not verified) Mon, 06/19/2023 - 13:02

Hanna Lyle, Suryansh Singh, Elena Magnano, Silvia Nappini, Federica Bondino, Sadegh Yazdi,* and Tanja Cuk*

ACS Catalysis 2023, DOI: https://pubs.acs.org/doi/full/10.1021/acscatal.3c00779

The oxygen evolution reaction (OER) from water, while more stable on transition metal oxide surfaces than others, has nonetheless proved to be concomitant with charge-induced surface degradation. Since heterogeneous and nanostructured electrodes are often used and with a large excitation area, the degradation can be difficult to quantify. Here, we utilize single crystalline SrTiO₃, highly efficient photoexcitation of the OER, and a focused laser to spatially define the degradation. A repetitive, ultrafast laser pulse above the band gap energy is employed, which allows for highly varied exposure of the surface using different scan methods. It also connects the work to the OER and its time-resolved mechanisms. By characterizing the degradation using optical spectroscopy and electron microscopy, the material dissolution constitutes an upper bound of 6% of the charge passed in a pH 13 electrolyte, while for pH 7, it reaches 23%; the pH dependence is anticorrelated with the ultrafast population of trapped charge. Although a minority component, the remarkable consistency of the 6% upper bound in the pH 13 electrolyte across a large range of linearly increasing degradation volumes and changing electrode composition defines a dominant lattice dissolution reaction as thermodynamically concomitant with the OER. Along with the pH dependence, the elemental composition of the degraded layer quantified by energy-dispersive and photoelectron and absorption X-ray spectroscopy suggests the relevance of certain chemical cation redeposition reactions. Altogether, using spatially and temporally defined photoexcitation of a crystalline surface provides a means to quantify semiconducting transition metal oxide degradation during the OER and constricts its mechanisms.

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Experimental detection of intermediates of the oxygen evolution reaction at aqueous metal-oxide interfaces

Anonymous — Mon, 19 Jun 2023 18:51:44 +0000

Experimental detection of intermediates of the oxygen evolution reaction at aqueous metal-oxide interfaces Anonymous (not verified) Mon, 06/19/2023 - 12:51

Tanja Cuk and Jin Suntivich

Encyclopedia of Solid-Liquid Interfaces, Edited by Wandelt and Bussetti 2023, DOI (current, online): https://doi.org/10.1016/B978-0-323-85669-0.00082-9

The oxygen evolution reaction (OER) from water is a critical component of a sustainable energy future; however, its mechanism has proved difficult to identify experimentally. This complexity is due to the elusive nature of electron and proton transfer intermediates that form within an interfacial water network and are buried at the solid–liquid interface. Here, we summarize recent measurements identifying the first two electron and proton transfer intermediates, e.g., OH^∗ and O∗, on metallic oxide surfaces prior to the OER cycle, and the first electron and proton transfer intermediate, OH^∗, as a metastable species during OER on a photo-excited, semiconducting oxide surface. These measurements provide information on the free energies of the intermediates, such that they can be used to approximate the reaction energy landscape of the catalytic cycle. We also highlight questions concerning the role that the interfacial environment (e.g., pH, interfacial water structure, and interfacial electric fields) plays in determining intermediate populations and their reaction kinetics.

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Moderate Electron Doping Assists in Dissociating Water on a Transition Metal Oxide Surface (n-SrTiO3)

Anonymous — Mon, 13 Mar 2023 03:10:36 +0000

Moderate Electron Doping Assists in Dissociating Water on a Transition Metal Oxide Surface (n-SrTiO3) Anonymous (not verified) Sun, 03/12/2023 - 21:10

Christen Courter, James Stewart, and Tanja Cuk*

Journal of Physical Chemistry C, 2023, DOI: https://doi.org/10.1021/acs.jpcc.2c07969

Water dissociation on transition metal oxide (TMO) surfaces regulates their catalytic activity in aqueous media. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) has differentiated TMO surfaces by the population of their first hydration layer on a scale between water molecularly absorbed and water fully dissociated into hydroxyl groups. Here, we show that electron-doping a single TMO (SrTiO₃: STO) can also span this range, with the data on lightly (0.1 wt % Nb) and moderately (0.7 wt % Nb) doped STO suggestive of partial and full water dissociation, respectively. The hydroxyl coverage is a factor of 9 greater in 0.7% Nb STO than in 0.1% Nb STO at low relative humidity (∼10^–3 % RH) and a factor of 2 greater at 1% RH, for which multilayers have already formed. Given the lack of a clear differentiation in surface morphology and termination, stoichiometry, or chemical environment of the two doped surfaces, the suggestion is made that the factor of ∼10 increase in electron density is the most likely origin of the marked increase in water dissociation across RH. Nonetheless, since the electron density delocalizes across many titanium oxygen bonds while surface characterizations are site-based, defining similar enough surfaces for which such a collective effect dominates remains a topic of future work. This work provides a benchmark for the effect of delocalized electron density, which can now be further tested by theoretical calculations and a broader material scope of low-to-moderately doped TMOs.

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Coherent Acoustic Interferometry during the Photodriven Oxygen Evolution Reaction Associates Strain Fields with the Reactive Oxygen Intermediate (Ti–OH*)

Anonymous — Mon, 04 Oct 2021 19:51:33 +0000

Coherent Acoustic Interferometry during the Photodriven Oxygen Evolution Reaction Associates Strain Fields with the Reactive Oxygen Intermediate (Ti–OH*) Anonymous (not verified) Mon, 10/04/2021 - 13:51

Suryansh Singh, Hanna Lyle, Luca D'Amario, Elena Magnano, Ilya Vinogradov*, and Tanja Cuk*

J. Am. Chem. Soc., 2021, 143, 39, 15984, DOI: 10.1021/jacs.1c04976

The oxygen evolution reaction (OER) from water requires the formation of metastable, reactive oxygen intermediates to enable oxygen–oxygen bond formation. Conversely, such reactive intermediates could also structurally modify the catalyst. A descriptor for the overall catalytic activity, the first electron and proton transfer OER intermediate from water, (M–OH*), has been associated with significant distortions of the metal–oxygen bonds upon charge-trapping. Time-resolved spectroscopy of in situ, photodriven OER on transition metal oxide surfaces has characterized M–OH* for the charge trapping and the symmetry of the lattice distortions by optical and vibrational transitions, respectively, but had yet to detect an interfacial strain field arising from a surface coverage of M–OH*. Here, we utilize picosecond, coherent acoustic interferometry to detect the uniaxial strain normal to the SrTiO₃/aqueous interface directly caused by Ti–OH*. The spectral analysis applies a fairly general methodology for detecting a combination of the spatial extent, magnitude, and generation time of the interfacial strain through the coherent oscillations’ phase. For lightly n-doped SrTiO₃, we identify the strain generation time (1.31 ps), which occurs simultaneously with Ti–OH* formation, and a tensile strain of 0.06% (upper limit 0.6%). In addition to fully characterizing this intermediate across visible, mid-infrared, and now GHz-THz probes on SrTiO₃, we show that strain fields occur with the creation of some M–OH*, which modifies design strategies for tuning catalytic activity and provides insight into photo-induced degradation so prevalent for OER. To that end, the work put forth here provides a unique methodology to characterize intermediate-induced interfacial strain across OER catalysts.

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One-Electron Water Oxidation Intermediate on TiO2 P25 Probed by Ultrafast Attenuated Total Reflection

Anonymous — Mon, 04 Oct 2021 19:39:37 +0000

One-Electron Water Oxidation Intermediate on TiO2 P25 Probed by Ultrafast Attenuated Total Reflection Anonymous (not verified) Mon, 10/04/2021 - 13:39

Xihan Chen* and Tanja Cuk

J. Phys. Chem. C 2021, 125, 33, 18204, DOI: 10.1021/acs.jpcc.1c05026

Water oxidation is considered as one of the most important reactions in solar-to-fuel generation. The initial catalytic intermediates formed on an ultrafast timescale play a great role in controlling water oxidation reaction. Here, we use ultrafast in situ infrared attenuated total reflectance spectroscopy to study the initial water oxidation intermediates at a state-of-the-art TiO₂ P25/aqueous interface. We observe a Ti–O vibration near 850 cm^–1 possibly in the anatase phase, suggested to be a subsurface vibration as a result of hole localization on the P25 surfaces. Such a subsurface Ti–O vibration is found to couple to reactant dynamics (water librations). This experiment suggests that a subsurface vibration could be a distinctive infrared reporter of reaction intermediates for water oxidation on titania surfaces.

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The electron-transfer intermediates of the oxygen evolution reaction (OER) as polarons by in-situ spectroscopy

Anonymous — Mon, 26 Apr 2021 18:59:45 +0000

The electron-transfer intermediates of the oxygen evolution reaction (OER) as polarons by in-situ spectroscopy Anonymous (not verified) Mon, 04/26/2021 - 12:59

Hanna Lyle, Suryansh Singh, Michael Paolino, Ilya Vinogradov, and Tanja Cuk*

Physical Chemistry Chemical Physics, 2021, 33, 24984 Invited Perspective, DOI: 10.1039/D1CP01760H (Featured Inside Front Cover)

The conversion of diffusive forms of energy (electrical and light) into short, compact chemical bonds by catalytic reactions regularly involves moving a carrier (electron or hole) from an environment that favors delocalization to one that favors localization. While delocalization lowers the energy of the carrier through its kinetic energy, localization creates a polarization around the carrier that traps it in a potential energy minimum. The trapped carrier and its local distortion—termed a polaron in solids—can play a role as a highly reactive intermediate within energy-storing catalytic reactions but is rarely discussed as such. Here, we present this perspective of the polaron as a catalytic intermediate through recent in-situ and time-resolved spectroscopic investigations of photo-triggered electrochemical reactions at material surfaces. The focus is on hole-trapping at metal-oxygen bonds, denoted M-OH^*, in the context of the oxygen evolution reaction (OER) from water. The potential energy surface for the hole-polaron defines the structural distortions from the periodic lattice and the resulting “active” site of catalysis. This perspective will highlight how current and future time-resolved, multi-modal probes can use spectroscopic signatures of M-OH^* polarons to obtain kinetic and structural information on the individual reaction steps of OER. A particular motivation is to provide the background needed for eventually relating this information to relevant catalytic descriptors by free energies. Finally, the formation of the O-O chemical bond from the consumption of M-OH^*, required to release O₂ and store energy in H₂, will be discussed as the next target for experimental investigations.

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