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25 pages, 5549 KB

Open AccessReview

Synchrotron X-Ray Techniques for In Situ or Microscopic Study of Passive Films on Industrial Alloys: A Mini Review

by Jinshan Pan

Corros. Mater. Degrad. 2025, 6(4), 56; https://doi.org/10.3390/cmd6040056 - 4 Nov 2025

Cited by 2 | Viewed by 1943

The spontaneous formation and stability of a protective passive film on a metal surface are crucial for the metal material’s corrosion resistance during its service life. Passive films have been extensively studied, and our understanding of passive films has been significantly improved with the development of advanced analytical techniques. Modern synchrotron X-ray sources offer unprecedented possibilities for detailed analyses of passive films and for in situ and operando studies of passive films in both gaseous/aqueous environments, as well as in electrochemical environments. This mini review presents a short summary of recent studies on passive films, mainly focusing on stainless steels and nickel-base alloys, which utilize state-of-the-art synchrotron X-ray techniques, particularly X-ray photoelectron spectroscopy (XPS), often in combination with other synchrotron techniques such as X-ray adsorption, diffraction, reflectivity, and fluorescence. These reports demonstrate that synchrotron-based techniques greatly improve probing sensitivity and spatial resolution, enabling in situ and operando studies of passive films at solid–liquid interfaces. These studies reveal changes in the passive film and underlying alloy layer, highlighting the important role of hydroxides, as well as the inhomogeneity in passive films associated with the complex microstructures in advanced industrial alloys. Full article

(This article belongs to the Special Issue Atmospheric Corrosion, Surface Electrochemistry and Environmental Degradation of Materials: In Honor of Prof. Christofer Leygraf)

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13 pages, 3647 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Structural Behaviour and Charge-Compensation Mechanism in Li₂Fe_1−xCo_xSeO Solid Solutions during Reversible Delithiation

by Mikhail V. Gorbunov and Daria Mikhailova

Processes 2024, 12(4), 756; https://doi.org/10.3390/pr12040756 - 9 Apr 2024

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Abstract

The constantly growing demand for renewable electrical energy keeps the continuation of battery-related research imperative. In spite of significant progress made in the development of Na- and K-ion systems, Li-ion batteries (LIBs) still prevail in the fields of portative devices and electric or hybrid vehicles. Since the amount of lithium on our planet is significantly limited, studies dedicated to the search for and development of novel materials, which would make LIBs more efficient in terms of their specific characteristics and life lengths, are necessary. Investigations of less industry-related systems are also important, as they provide general knowledge which helps in understanding directions and strategies for the improvement of applied materials. The current paper represents a comprehensive study of cubic Li₂Fe_1−xCo_xSeO compounds with an anti-perovskite structure. These solid solutions demonstrate both cationic and anionic electrochemical activity in lithium cells while being applied as cathodes. Cobalt cations remain inactive; however, their amount in the structure defines if the Se⁰/Se²⁻ or Fe³⁺/Fe²⁺ redox couple dominates the charge compensation mechanism upon (de)lithiation. Apart from that, cobalt affects the structural stability of the materials during cycling. These effects were evaluated by means of operando XRD and XAS techniques. The outcomes can be useful for both fundamental and practice-relevant research. Full article

(This article belongs to the Special Issue Advanced Lithium Battery Electrode Materials)

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18 pages, 3572 KB

Open AccessArticle

Sample Environment for Operando Hard X-ray Tomography—An Enabling Technology for Multimodal Characterization in Heterogeneous Catalysis

by Johannes Becher, Sebastian Weber, Dario Ferreira Sanchez, Dmitry E. Doronkin, Jan Garrevoet, Gerald Falkenberg, Debora Motta Meira, Sakura Pascarelli, Jan-Dierk Grunwaldt and Thomas L. Sheppard

Catalysts 2021, 11(4), 459; https://doi.org/10.3390/catal11040459 - 1 Apr 2021

Cited by 11 | Viewed by 4912

Abstract

Structure–activity relations in heterogeneous catalysis can be revealed through in situ and operando measurements of catalysts in their active state. While hard X-ray tomography is an ideal method for non-invasive, multimodal 3D structural characterization on the micron to nm scale, performing tomography under controlled gas and temperature conditions is challenging. Here, we present a flexible sample environment for operando hard X-ray tomography at synchrotron radiation sources. The setup features are discussed, with demonstrations of operando powder X-ray diffraction tomography (XRD-CT) and energy-dispersive tomographic X-ray absorption spectroscopy (ED-XAS-CT). Catalysts for CO₂ methanation and partial oxidation of methane are shown as case studies. The setup can be adapted for different hard X-ray microscopy, spectroscopy, or scattering synchrotron radiation beamlines, is compatible with absorption, diffraction, fluorescence, and phase-contrast imaging, and can operate with scanning focused beam or full-field acquisition mode. We present an accessible methodology for operando hard X-ray tomography studies, which offer a unique source of 3D spatially resolved characterization data unavailable to contemporary methods. Full article

(This article belongs to the Special Issue 2020s Vision on Catalysts: Operando Characterization Methods)

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15 pages, 3373 KB

Open AccessArticle

Understanding the Deactivation Phenomena of Small-Pore Mo/H-SSZ-13 during Methane Dehydroaromatisation

by Miren Agote-Arán, Anna B. Kroner, David S. Wragg, Wojciech A. Sławiński, Martha Briceno, Husn U. Islam, Igor V. Sazanovich, María E. Rivas, Andrew W. J. Smith, Paul Collier, Inés Lezcano-González and Andrew M. Beale

Molecules 2020, 25(21), 5048; https://doi.org/10.3390/molecules25215048 - 30 Oct 2020

Cited by 10 | Viewed by 4070

Abstract

Small pore zeolites have shown great potential in a number of catalytic reactions. While Mo-containing medium pore zeolites have been widely studied for methane dehydroaromatisation (MDA), the use of small pore supports has drawn limited attention due to the fast deactivation of the catalyst. This work investigates the structure of the small pore Mo/H-SSZ-13 during catalyst preparation and reaction by operando X-ray absorption spectroscopy (XAS), in situ synchrotron powder diffraction (SPD), and electron microscopy; then, the results are compared with the medium pore Mo/H-ZSM-5. While SPD suggests that during catalyst preparation, part of the MoO_x anchors inside the pores, Mo dispersion and subsequent ion exchange was less effective in the small pore catalyst, resulting in the formation of mesopores and Al₂(M_OO₄)₃ particles. Unlike Mo/H-ZSM-5, part of the Mo species in Mo/H-SSZ-13 undergoes full reduction to Mo⁰ during MDA, whereas characterisation of the spent catalyst indicates that differences also exist in the nature of the formed carbon deposits. Hence, the different Mo speciation and the low performance on small pore zeolites can be attributed to mesopores formation during calcination and the ineffective ion exchange into well dispersed Mo-oxo sites. The results open the scope for the optimisation of synthetic routes to explore the potential of small pore topologies. Full article

(This article belongs to the Special Issue Zeolitic Microporous Materials and Their Applications)

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12 pages, 2130 KB

Open AccessArticle

In Situ Study of Graphene Oxide Quantum Dot-MoS_x Nanohybrids as Hydrogen Evolution Catalysts

by Marco Favaro, Mattia Cattelan, Stephen W. T. Price, Andrea E. Russell, Laura Calvillo, Stefano Agnoli and Gaetano Granozzi

Surfaces 2020, 3(2), 225-236; https://doi.org/10.3390/surfaces3020017 - 16 Jun 2020

Cited by 5 | Viewed by 4727

Abstract

Graphene quantum dots (GOQDs)-MoS_x nanohybrids with different MoS_x stoichiometries (x = 2 and 3) were prepared in order to investigate their chemical stability under hydrogen evolution reaction (HER) conditions. Combined photoemission/electrochemical (XPS/EC) measurements and operando X-ray absorption spectroscopy (XAS) were employed to determine the chemical changes induced on the MoS_x-based materials as a function of the applied potential. This in situ characterization indicates that both MoS₂ and MoS₃ materials are stable under operating conditions, although sulfur terminal sites in the MoS₃ nanoparticles are converted from S-dimer (S₂²⁻) to S-monomer (S²⁻), which constitute the first sites where the hydrogen atoms are adsorbed for their subsequent evolution. In order to complete the characterization of the GOQDs-MoS_x nanohybrids, the composition and particle size were determined by X-ray photoemission spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy; whereas the HER activity was studied by conventional electrochemical techniques. Full article

(This article belongs to the Special Issue Surface Science and Catalysis of Graphene-Related 2D Materials)

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