University of Oulu

Shulda S, Bell RT, Strange NA, Metzroth L, Heinselman KN, Sainio S, Roychoudhury S, Prendergast D, McDaniel AH and Ginley DS (2022), Synchrotron-based techniques for characterizing STCH water-splitting materials. Front. Energy Res. 10:931364. doi: 10.3389/fenrg.2022.931364

Synchrotron-based techniques for characterizing STCH water-splitting materials

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Author: Shulda, Sarah1; Bell, Robert T.1; Strange, Nicholas A.2;
Organizations: 1National Renewable Energy Laboratory, Golden, CO, United States
2Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, United States
3Microelectronics Research Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu, Oulu, Finland
4Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
5Sandia National Laboratory, Livermore, CA, United States
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.1 MB)
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Language: English
Published: Frontiers Media, 2022
Publish Date: 2023-04-21


Understanding the role of oxygen vacancy–induced atomic and electronic structural changes to complex metal oxides during water-splitting processes is paramount to advancing the field of solar thermochemical hydrogen production (STCH). The formulation and confirmation of a mechanism for these types of chemical reactions necessitate a multifaceted experimental approach, featuring advanced structural characterization methods. Synchrotron X-ray techniques are essential to the rapidly advancing field of STCH in part due to properties such as high brilliance, high coherence, and variable energy that provide sensitivity, resolution, and rapid data acquisition times required for the characterization of complex metal oxides during water-splitting cycles. X-ray diffraction (XRD) is commonly used for determining the structures and phase purity of new materials synthesized by solid-state techniques and monitoring the structural integrity of oxides during water-splitting processes (e.g., oxygen vacancy–induced lattice expansion). X-ray absorption spectroscopy (XAS) is an element-specific technique and is sensitive to local atomic and electronic changes encountered around metal coordination centers during redox. While in operando measurements are desirable, the experimental conditions required for such measurements (high temperatures, controlled oxygen partial pressures, and H2O) practically necessitate in situ measurements that do not meet all operating conditions or ex situ measurements. Here, we highlight the application of synchrotron X-ray scattering and spectroscopic techniques using both in situ and ex situ measurements, emphasizing the advantages and limitations of each method as they relate to water-splitting processes. The best practices are discussed for preparing quenched states of reduction and performing synchrotron measurements, which focus on XRD and XAS at soft (e.g., oxygen K-edge, transition metal L-edges, and lanthanide M-edges) and hard (e.g., transition metal K-edges and lanthanide L-edges) X-ray energies. The X-ray absorption spectra of these complex oxides are a convolution of multiple contributions with accurate interpretation being contingent on computational methods. The state-of-the-art methods are discussed that enable peak positions and intensities to be related to material electronic and structural properties. Through careful experimental design, these studies can elucidate complex structure–property relationships as they pertain to nonstoichiometric water splitting. A survey of modern approaches for the evaluation of water-splitting materials at synchrotron sources under various experimental conditions is provided, and available software for data analysis is discussed.

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Series: Frontiers in energy research
ISSN: 2296-598X
ISSN-E: 2296-598X
ISSN-L: 2296-598X
Volume: 10
Article number: 931364
DOI: 10.3389/fenrg.2022.931364
Type of Publication: A1 Journal article – refereed
Field of Science: 222 Other engineering and technologies
Funding: Funding was provided by the HydroGEN Advanced Water Splitting Materials Consortium, established as part of the Energy Materials Network under the United States Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office, under Award Number DE-EE0008087. Computational work (SR and DP) was carried out using supercomputing resources of the National Energy Research Scientific Computing Center (NERSC). The work by SR and DP at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the United States Department of Energy under Contract No. DEAC02-05CH11231. The use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the United States Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. SS acknowledges funding from the Walter Ahlstrom Foundation. SS has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 841621.
EU Grant Number: (841621) TACOMA - Towards Application specific tailoring of CarbOn nanoMAterials
Dataset Reference: The original contributions presented in the study are included in the article/Supplementary Material; further inquiries can be directed to the corresponding author.
Copyright information: © The Authors 2022. This work is authored by Sarah Shulda, Robert T. Bell, Nicholas A. Strange, Lucy Metzroth, Karen N. Heinselman, Sami Sainio, Subhayan Roychoudhury, David Prendergast, Anthony H. McDaniel and David S. Ginley © 2022 Alliance for Sustainable Energy, LLC and Sandia National Laboratory. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).