Operando XAS Techniques: Past, Present, and Future

Roth, Christina; Ramaker, David E.

doi:10.1002/9780470630693.ch17

Cited by 9 publications

(8 citation statements)

References 103 publications

(118 reference statements)

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“…This theoretical line shape has been previously reported by Teliska et al , and is consistent with relevant DFT calculations − ,, for 3-fold fcc or bridged bonded O at these potentials. The strong adsorption of O[H] is also consistent with the results from the EXAFS fits, which show that the Pt–Pt coordination number is significantly reduced at 0.84 V, this occurring because O[H] adsorption decreases the Pt–Pt scattering (each 3-fold O decreases the Pt–Pt scattering more than each atop OH, but either OH or O adsorption decreases it some). ,, The Δμ spectra for 100 mM Cu appear to have different features present, and this will be explained after we consider the results for upd Cu in sulfuric acid.…”

Section: Resultssupporting

confidence: 76%

Fundamental Aspects of ad-Metal Dissolution and Contamination in Low and Medium Temperature Fuel Cell Electrocatalysis: A Cu Based Case Study Using In Situ Electrochemical X-ray Absorption Spectroscopy

et al. 2013

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Electrochemical methods (cyclic voltammetry and rotating ring disk electrode) and in situ X-ray absorption spectroscopy (XAS) were used in conjunction to study copper adsorption onto carbon-supported platinum nanoparticles over the operating potential range of proton exchange membrane fuel cell (PEMFC) cathodes and anodes (∼0.0−1.0 V vs the reference hydrogen electrode, RHE). Our purpose was to better understand the detrimental effects of Cu leaching from high-activity dealloyed PtCu x electrocatalysts. These studies were conducted in CuSO 4 -doped 0.1 N solutions of HClO 4 and H 2 SO 4 under both inert and oxygenated conditions. Over the anode potential range (∼0.0−0.3 V vs RHE), concentrations of Cu 2+ as low as 10 μM were found to coat the active Pt surfaces, thereby drastically inhibiting the hydrogen oxidation reaction. Over the Cu underpotential deposition region (0.35−0.70 V vs RHE), Cu 2+ concentrations ≥0.05 mM resulted in Cu deposition onto Pt. This was found to lower the oxygen reduction reaction activity of Pt by skewing the reaction mechanism toward the twoelectron pathway (peroxide production) away from the desired four-electron pathway (water). Electrochemical methods were inconclusive as to the effects of Cu 2+ at potentials greater than 0.84 V. While in situ Pt L 3 edge extended X-ray absorption fine structure (EXAFS) revealed definitive Pt−Cu scattering paths below 0.84 V, Cu was not observed at higher potentials. The Δμ analysis of X-ray absorption near-edge structure (XANES) revealed that Cu(O) coadsorbs under high Cu 2+ concentrations in HClO 4 , and that H 2 SO 4 results in Cu(O) coadsorption at lower concentrations. Extending the Δμ analysis to lower potentials revealed the interplay of Cu 2+ , O(H), and H + coadsorption with respect to potential, Cu 2+ concentration, and sparging environment (inert or oxygenated). These studies verify that Cu leaching from PtCu x -alloy electrocatalysts can have detrimental effects on both the anode and cathode sides of a PEMFC, and similar experiments can be extended to probe the adsorption effects of other transition metals from PtM x alloys.

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Section: Resultssupporting

confidence: 76%

Fundamental Aspects of ad-Metal Dissolution and Contamination in Low and Medium Temperature Fuel Cell Electrocatalysis: A Cu Based Case Study Using In Situ Electrochemical X-ray Absorption Spectroscopy

et al. 2013

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“…Insight into the impact of potential-induced structural degradation (roughening and/or dissolution) on electronic properties (that is, the change in the oxidation state of Ru cations) can be obtained from a series of measurements performed with X-ray absorption near-edge spectroscopy (XANES) 43 . For SRO(001), the XANES spectrum at 0.95 V is consistent with the Ru 4 þ oxidation state, as expected for stoichiometric SrRuO 3 (Fig.…”

Section: Resultsmentioning

confidence: 99%

Functional links between stability and reactivity of strontium ruthenate single crystals during oxygen evolution

et al. 2014

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In developing cost-effective complex oxide materials for the oxygen evolution reaction, it is critical to establish the missing links between structure and function at the atomic level. The fundamental and practical implications of the relationship on any oxide surface are prerequisite to the design of new stable and active materials. Here we report an intimate relationship between the stability and reactivity of oxide catalysts in exploring the reaction on strontium ruthenate single-crystal thin films in alkaline environments. We determine that for strontium ruthenate films with the same conductance, the degree of stability, decreasing in the order (001)4(110)4(111), is inversely proportional to the activity. Both stability and reactivity are governed by the potential-induced transformation of stable Ru 4 þ to unstable Ru n44 þ . This ordered(Ru 4 þ )-to-disordered(Ru n44 þ ) transition and the development of active sites for the reaction are determined by a synergy between electronic and morphological effects.

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“…Differential ("field on" minus "field off") XAS detects only active species that respond to the electric field; passive (spectator) species do not contribute to the differential signal. This approach has been used previously in a number of studies, including those on magnetostriction, 19 catalytic and electrocatalytic activity, [20][21][22][23] and Ar-induced surface restructuring of Pd nanoclusters. 24 XAS measurements of the Ce and Gd L III -edges were performed on the Gd-doped ceria electrostriction samples in fluorescence mode with a focused X-ray beam, spot size $ 1 mm 2 .…”

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confidence: 99%

In-situ extended X-ray absorption fine structure study of electrostriction in Gd doped ceria

Korobko

Lerner

et al. 2015

Applied Physics Letters

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Studying electric field-induced structural changes in ceramics is challenging due to the very small magnitude of the atomic displacements. We used differential X-ray absorption spectroscopy, an elementally specific and spatially sensitive method, to detect such changes in Gd-doped ceria, recently shown to exhibit giant electrostriction. We found that the large electrostrictive stress generation can be associated with a few percent of unusually short Ce-O chemical bonds that change their length and degree of order under an external electric field. The remainder of the lattice is reduced to the role of passive spectator. This mechanism is fundamentally different from that in electromechanically active materials currently in use. V

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Operando XAS Techniques: Past, Present, and Future

Cited by 9 publications

References 103 publications

Fundamental Aspects of ad-Metal Dissolution and Contamination in Low and Medium Temperature Fuel Cell Electrocatalysis: A Cu Based Case Study Using In Situ Electrochemical X-ray Absorption Spectroscopy

Fundamental Aspects of ad-Metal Dissolution and Contamination in Low and Medium Temperature Fuel Cell Electrocatalysis: A Cu Based Case Study Using In Situ Electrochemical X-ray Absorption Spectroscopy

Functional links between stability and reactivity of strontium ruthenate single crystals during oxygen evolution

In-situ extended X-ray absorption fine structure study of electrostriction in Gd doped ceria

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