QEXAFS: Techniques and Scientific Applications for Time‐Resolved XAS

Time-resolved operando studies of carbon supported Pd nanoparticles under hydrogenation reactions by X-ray diffraction and absorption

“…A repetition rate of 0.2 Hz (one XRPD pattern every 5 s) was needed to follow the structural oscillation of the core. Unfortunately, 5 s were insufficient to obtain an EXAFS spectrum in quick EXAFS mode 85 with a sufficient signal to noise (on our Pd/C sample hosted in a capillary) to allow an accurate determination of the structure of the shell. This experiment should be repeated using an EXAFS dispersive beamline.…”

Operando Time-Resolved X-ray Absorption Fine Structure Study for Pt Oxidation Kinetics on Pt/C and Pt3Co/C Cathode Catalysts by Polymer Electrolyte Fuel Cell Voltage Operation Synchronized with Rapid O2 Exposure

“…X-ray absorption fine structure (XAFS) analysis is a powerful tool for examining the chemical state and local coordination of each element. The high transmittance of hard X-rays enables operando time-resolved quick-XAFS (QXAFS) measurements − of electrocatalysts in MEAs under practical PEFC operating conditions, showing the structural kinetics of cathode electrocatalysts under humidified N 2 atmosphere. − For example, we have reported the structural kinetics of a Pt/C, , Pt 3 Co/C, and Pt 3 Ni/C ,, cathode catalysts for the voltage operation between 0.4–1.0 V, and the transitional states of a Pt/C cathode catalyst during PEFC loading with transient voltage . The operando time-resolved QXAFS analysis of the Pt 3 Co/C catalyst under the cathode atmosphere of humidified N 2 revealed the positive rate enhancement of the Pt–Pt bond reforming from 1.0 to 0.4 V, which is suggested to be a reason for high durability of the Pt 3 Co/C catalyst. − However, the reported operando time-resolved XAFS measurements were performed under humidified N 2 atmosphere without O 2 at the cathode, and the observed dynamic events at the cathode are caused by the redox processes of the Pt catalysts with H 2 O.…”

Protagonists and spectators during photocatalytic solar water splitting with SrTaOxNy oxynitride

“…Furthermore, improvements in signal-to-noise ratio can be achieved through analysis of ME-XAS with phase sensitive detection (PSD). 47,48,49,50 PSD converts time-resolved XAS data into a set of phase (φ PSD ) resolved data akin to a digital lock-in amplifier, enhancing the sensitivity of the ME-XAS experiment to spectral responses that match the frequency of the chopped light stimulus. More information on the PSD approach is included in the Supplementary Discussion.…”

“…The time resolved XAS were measured using the quickXAS method 64 at the SuperXAS beamline at the SLS, Paul Scherrer Institut in Switzerland. The polychromatic beam of the 2.9 Tesla superbend was collimated by a Si-coated collimating mirror and subsequently monochromatised by a Si (111) channel-cut crystal of the quickXAS monochromator, which oscillated at 1 Hz frequency with an acquisition time of 500 milliseconds per spectrum.…”