A refraction correction for buried interfaces applied to in situ grazing-incidence X-ray diffraction studies on Pd electrodes

Abstract

In situ characterization of electrochemical systems can provide deep insights into the structure of electrodes under applied potential. Grazing-incidence X-ray diffraction (GIXRD) is a particularly valuable tool owing to its ability to characterize the near-surface structure of electrodes through a layer of electrolyte, which is of paramount importance in surface-mediated processes such as catalysis and adsorption. Corrections for the refraction that occurs as an X-ray passes through an interface have been derived for a vacuum–material interface. In this work, a more general form of the refraction correction was developed which can be applied to buried interfaces, including liquid–solid interfaces. The correction is largest at incidence angles near the critical angle for the interface and decreases at angles larger and smaller than the critical angle. Effective optical constants are also introduced which can be used to calculate the critical angle for total external reflection at the interface. This correction is applied to GIXRD measurements of an aqueous electrolyte–Pd interface, demonstrating that the correction allows for the comparison of GIXRD measurements at multiple incidence angles. This work improves quantitative analysis of d-spacing values from GIXRD measurements of liquid–solid systems, facilitating the connection between electrochemical behavior and structure under in situ conditions.

Dynamics and Hysteresis of Hydrogen Intercalation and Deintercalation in Palladium Electrodes: A Multimodal In Situ X-ray Diffraction, Coulometry, and Computational Study

“…The XRD measurements were corrected for refraction at a liquid−solid interface. 37 The H/Pd ratio was calculated by integrating the charge passed during a 5 min period following a potential step to +0.90 V vs RHE. This potential was chosen to be sufficiently positive for all hydrogen stored within the sample to deintercalate.…”

“…For the time-resolved measurements, the area detector was fixed at a 2θ position that allowed us to monitor the position of the Pd(111) and β-PdH x (111) peaks simultaneously. The XRD measurements were corrected for refraction at a liquid–solid interface …”

Discovery of LaAlO3 as an efficient catalyst for two-electron water electrolysis towards hydrogen peroxide

“…The 15.7° peak is overlapped by the (110) peak of LaAlO 3 and the FTO substrate peak; however, the HRTEM confirms the (110) facet for LaAlO 3 . Since the GIXRD was collected with the X-rays with its incident energy of 17.0 keV and wavelength of 0.729 Å 60 , the two theta values are different from those with the general Cu Kα (1.54 Å). All the above results confirm that the crystal structure of LaAlO 3 is cubic perovskite.…”

Depolarization mitigated in ferroelectric Hf 0.5Zr 0.5O 2 ultrathin films (< 5 nm) on Si substrate by interface engineering

“…(iii) The 2θ position of the fitted peak could be slightly shifted to higher 2θ because of the grazing incidence geometry. The 2θ position of the diffraction peak has often been reported to shift to higher 2θ as the incidence angle decreases [45], which is largely attributable to the refraction effect [46].…”