Monitoring dynamic electrochemical processes with in situ ptychography

Abstract

The present work reports novel soft X-ray Fresnel CDI ptychography results, demonstrating the potential of this method for dynamic in situ studies. Specifically, in situ ptychography experiments explored the electrochemical fabrication of Codoped Mn-oxide/polypyrrole nanocomposites for sustainable and cost-effective fuel-cell air-electrodes. Oxygen-reduction catalysts based on Mn-oxides exhibit relatively high activity, but poor durability: doping with Co has been shown to improve both reduction rate and stability. In this study, we examine the chemical state distribution of the catalytically crucial Co dopant to elucidate details of the Co dopant incorporation into the Mn/polymer matrix. The measurements were performed using a custom-made three-electrode thin-layer microcell, developed at the TwinMic beamline of Elettra Synchrotron during a series of experiments that were continued at the SXRI beamline of the Australian Synchrotron. Our time-resolved ptychography-based investigation was carried out in situ after two representative growth steps, controlled by electrochemical bias. In addition to the observation of morphological changes, we retrieved the spectroscopic information, provided by multiple ptychographic energy scans across Co L 3 -edge, shedding light on the doping mechanism and demonstrating a general approach for the molecular-level investigation complex multimaterial electrodeposition processes.

Development of electrochemical cells for spatially resolved analysis using a multi-technique approach: from conventional experiments to X-ray nanoprobe beamlines

“…Ptychography is one of the most advanced X-ray microscopy techniques for high-resolution imaging, because it uses a focused beam in conjunction with its scanning over the sample making it suitable for large samples (with sizes ranging from some micrometers to millimeters) and it is compatible with other scanning microscopy and electrochemical systems. [63][64][65] This technique stands out not only for achieving a spatial resolution beyond the size of the focused beam.…”

X-ray Spectroptychography

“…Only a few applications of in situ and operando spectroptychography have emerged to date. 39 In situ spectroptychography was examined at the Co L 3 edge (16 energies) for a working electrode of a Mn–Co/polypyrrole nanocomposite that had been subjected to 100 electrodeposition cycles. In these examples, the sample is stable over the time scale of the spectroscopic scans.…”

Soft X-ray Microscopy Techniques for Medical and Biological Imaging at TwinMic—Elettra

“…Indeed, the redundant information due to the oversampling allows computer algorithms to reconstruct reliably both the sample transmission function and the illuminating probe, recovering the amplitude and phase of both these signals. As in classical SXTM, by reconstructing a stack of images acquired at photon energies across the absorption edge of a specific chemical element, ptychography allows for XANES-type studies, as demonstrated in [64,65], providing sub-micrometric resolution chemical speciation.…”

“…In addition to ptychography experiments, the beamline has successfully tested the keyhole-CDI technique [61], which, by being a single-shot technique, is, in general, preferable for in situ dynamic studies, such as monitoring the dynamics of electrodeposition [64,65], but which can also be used for biological samples [66].…”