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The need for carbon‐neutralization technologies has prompted significant interest in developing materials for CO2 reduction. Donor–acceptor (D–A) based flexible porous coordination polymers {[Zn(o‐phen)(ndc)].(guest)}n, (guest = anthracene = 1‐Ant, and pyrene = 1‐Pyr) are reported as photocatalysts for CO2RR, yielding higher order CH4 product. Electron‐rich anthracene (Ant) and pyrene (Pyr) guests are confined within nanopores, forming D–A charge transfer (CT) complexes with o‐phen ligand of the host. CT interaction enhances visible light absorption and modulates excitonic properties of the photocatalyst by electronic push‐pull effect (exciton binding energy 87 meV for 1‐Ant and 104 meV for 1‐Pyr). Electron donation capability varies from Pyr to Ant, affecting catalytic properties; 1‐Ant yields 1.24 mmolg−1 of CH4 (0.47 mmolg−1 for 1‐Pyr) with CO as minor product. A mixed‐metal multivariate PCP {[Zn0.55Co0.45(o‐phen)(ndc)].(Ant)}n, (1′‐Ant) prepared based on solid‐solution approach by substituting Zn(II) with redox‐active Co(II) enhances CH4 production (2.79 mmolg−1, ≈94% selectivity). D–A CT complex harvests visible light and channels electrons to Co(II) for CO2RR. In situ DRIFTS and theoretical studies elucidate Co(II) site's role in CO2 binding and stabilizing reaction intermediates. This work underscores guest‐modulated electron transfer in PCPs for tailoring catalytic properties by introducing a redox‐active metal in a multivariate approach. [ABSTRACT FROM AUTHOR]

Understanding the structure–property relationship in electrocatalysts under working conditions is crucial for the rational design of novel and improved catalytic materials. This paper presents the Aarhus University reactor for electrochemical studies using X‐rays (AUREX) operando electrocatalytic flow cell, designed as an easy‐to‐use versatile setup with a minimal background contribution and a uniform flow field to limit concentration polarization and handle gas formation. The cell has been employed to measure operando total scattering, diffraction and absorption spectroscopy as well as simultaneous combinations thereof on a commercial silver electrocatalyst for proof of concept. This combination of operando techniques allows for monitoring of the short‐, medium‐ and long‐range structure under working conditions, including an applied potential, liquid electrolyte and local reaction environment. The structural transformations of the Ag electrocatalyst are monitored with non‐negative matrix factorization, linear combination analysis, the Pearson correlation coefficient matrix, and refinements in both real and reciprocal space. Upon application of an oxidative potential in an Ar‐saturated aqueous 0.1 M KHCO3/K2CO3 electrolyte, the face‐centered cubic (f.c.c.) Ag gradually transforms first to a trigonal Ag2CO3 phase, followed by the formation of a monoclinic Ag2CO3 phase. A reducing potential immediately reverts the structure to the Ag (f.c.c.) phase. Following the electrochemical‐reaction‐induced phase transitions is of fundamental interest and necessary for understanding and improving the stability of electrocatalysts, and the operando cell proves a versatile setup for probing this. In addition, it is demonstrated that, when studying electrochemical reactions, a high energy or short exposure time is needed to circumvent beam‐induced effects. [ABSTRACT FROM AUTHOR]

Transition metal oxides, especially cobalt oxides and hydroxides, are of great interest as precious metal free electrode materials for the oxygen evolution reaction (OER) in electrochemical and photoelectrochemical water splitting. Here, we present detailed studies of the potential‐ and pH‐dependent structure and structural stability of Co3O4 and CoOOH in neutral to alkaline electrolytes (pH 7 to 13), using operando surface X‐ray diffraction, atomic force microscopy, and electrochemical measurements. The experiments cover the pre‐OER and OER range and were performed on epitaxial Co3O4(111) and CoOOH(001) films electrodeposited on Au(111) single crystal electrodes. The CoOOH films were structurally perfectly stable under all experimental conditions, whereas Co3O4 films exhibit at all pH values reversible potential‐dependent structural transformations of a sub‐nanometer thick skin layer region at the oxide surface, as reported previously for pH 13 (F. Reikowski et al., ACS Catal. 2019, 9, 3811). The intrinsic OER activity at 1.65 V versus the reversible hydrogen electrode decreases strongly with decreasing pH, indicating a reaction order of 0.2 with respect to [OH−]. While the Co3O4 spinel is stable at pH 13, intermittent exposure to electrolytes with pH≤10 results in dissolution as well as gradual degradation of its OER activity in subsequent measurements at pH 13. [ABSTRACT FROM AUTHOR]

It is widely established that the electroreduction of carbon dioxide on a copper surface yields a spectrum of alcohols and hydrocarbons. But the selectivity of Cu toward a certain product is extremely poor as it forms a variety of reduced products concurrently. Controlling selectivity and overall performance depends on the modification of the Cu site and local environment. This study depicts how the product selectivity can be switched from C1 to C2 and multicarbon products by systematic incorporation of secondary metal (Pd) into the Cu lattice. Upon releasing the structural ordering from intermetallic to alloy and then to bimetallic, a systematic enhancement on the formation of C2 products from CO2 has been observed. Real‐time in situ X‐ray absorption spectroscopy (XAS) study showed the potential dependent evolution of Pd─Cu and Cu─Cu bonds in different Pd‐Cu‐based catalysts. The detailed analysis of in situ IR and Raman also determined the adsorbed intermediate species and helped to identify the mechanism. Computational studies show the feasibility of multicarbon product formation on bimetallic catalysts compared to alloy and intermetallic catalysts. The current density and the activity of the CO2 electroreduction have been enhanced by the utilization of the flow cell in the gas diffusion electrode configuration. [ABSTRACT FROM AUTHOR]

INSIGHT is a Python‐based software tool for processing and reducing 2D grazing‐incidence wide‐ and small‐angle X‐ray scattering (GIWAXS/GISAXS) data. It offers the geometric transformation of the 2D GIWAXS/GISAXS detector image to reciprocal space, including vectorized and parallelized pixel‐wise intensity correction calculations. An explicit focus on efficient data management and batch processing enables full control of large time‐resolved synchrotron and laboratory data sets for a detailed analysis of kinetic GIWAXS/GISAXS studies of thin films. It processes data acquired with arbitrarily rotated detectors and performs vertical, horizontal, azimuthal and radial cuts in reciprocal space. It further allows crystallographic indexing and GIWAXS pattern simulation, and provides various plotting and export functionalities. Customized scripting offers a one‐step solution to reduce, process, analyze and export findings of large in situ and operando data sets. [ABSTRACT FROM AUTHOR]

Presented here is an electrochemical three-electrode Gas Diffusion Electrode (GDE) cell tailored for operandoand in situ investigations of electrocatalytic processes, with a particular focus on X-ray scattering studies. The optimized cell is engineered to accommodate the minimal sample-detector distances requisite for comprehensive X-ray total scattering investigations. An in-depth understanding of catalytic processes requires their study under ‘working’ conditions. Configured as a flow-cell, the setup therefore enables the examination of electrocatalysts under high current densities and associated gas evolution phenomena, particularly pertinent for reactions like the oxygen evolution reaction (OER). Notably, its transparency simplifies cell alignment, troubleshooting, and facilitates scans through the catalyst layer, crucial for background corrections. Demonstrating its versatility, we showcase its utility through Small Angle X-ray Scattering (SAXS), X-ray Diffraction (XRD), and X-ray Pair Distribution Function (PDF) analyses of total scattering data.

A multielectrode-based electrochemical cell allows the structural characterization of an amorphous thin-film water oxidation catalyst under various electrochemical potentials using high-energy X-ray scattering and atomic pair distribution function (PDF) techniques. A multielectrode with five electrodes provides a sufficiently low background signal to enable high-energy X-ray scattering (HEXS) measurements and amplifies the extremely low HEXS signals from samples for high-resolution PDF analysis of in situ data from thinfilm catalysts. Glassy carbon (GC) creates a relatively low intensity HEXS pattern and is used as a working electrode. Instead of a three-dimensional (3D) porous electrode architecture, the flat geometry of the electrode enables various deposition techniques to be used for the preparation of a highly conductive metal oxide layer. PDF analysis demonstrates high spatial resolution for a 230 nm thick amorphous iridium oxide film deposited on two roughened 60 μm thick GC electrodes. The PDF analysis resolves the domain size and distinguishes changes in fine structure which are directly correlated with the structure and function of the catalysts. The results bring the opportunity to analyze the structure of nanometre-scale amorphous thin-film catalysts in an electrolyte-compatible and compact 3D-printed electrochemical cell in a threeelectrode configuration. [ABSTRACT FROM AUTHOR]

Operando powder X-ray diffraction (PXRD) is a widely employed method for the investigation of structural evolution and phase transitions in electrodes for rechargeable batteries. Due to the advantages of high brilliance and high X-ray energies, the experiments are often carried out at synchrotron facilities. It is known that the X-ray exposure can cause beam damage in the battery cell, resulting in hindrance of the electrochemical reaction. This study investigates the extent of X-ray beam damage during operando PXRD synchrotron experiments on battery materials with varying X-ray energies, amount of X-ray exposure and battery cell chemistries. Battery cells were exposed to 15, 25 or 35 keV X-rays (with varying dose) during charge or discharge in a battery test cell specially designed for operando experiments. The observed beam damage was probed by µPXRD mapping of the electrodes recovered from the operando battery cell after charge/discharge. The investigation reveals that the beam damage depends strongly on both the X-ray energy and the amount of exposure, and that it also depends strongly on the cell chemistry, i.e. the chemical composition of the electrode.

Operando powder X-ray diffraction (PXRD) is a widely employed method for the investigation of structural evolution and phase transitions in electrodes for rechargeable batteries. Due to the advantages of high brilliance and high X-ray energies, the experiments are often carried out at synchrotron facilities. It is known that the X-ray exposure can cause beam damage in the battery cell, resulting in hindrance of the electrochemical reaction. This study investigates the extent of X-ray beam damage during operando PXRD synchrotron experiments on battery materials with varying X-ray energies, amount of X-ray exposure and battery cell chemistries. Battery cells were exposed to 15, 25 or 35 keV X-rays (with varying dose) during charge or discharge in a battery test cell specially designed for operando experiments. The observed beam damage was probed by mPXRD mapping of the electrodes recovered from the operando battery cell after charge/discharge. The investigation reveals that the beam damage depends strongly on both the X-ray energy and the amount of exposure, and that it also depends strongly on the cell chemistry, i.e. the chemical composition of the electrode. [ABSTRACT FROM AUTHOR]

• surface science studies of electrochemical interfaces progressed greatly in the last 30 years. • studies provide detailed insights on structure and dynamics of adsorbate layers. • dynamic structural changes at electrodes under reaction conditions are revealed. Surface science studies of electrochemical interfaces and processes have gained increasing popularity in the last decades, owning to the increasing importance of electrochemistry for key technologies of the 21th century, especially in electric energy storage and conversion. In situ and operando surface-sensitive methods, such as scanning probe microscopy and surface X-ray diffraction, as well as complementary ab initio theory can provide atomic-scale information on solid electrode surface in contact with liquid electrolytes, including structural changes under reaction conditions. The level of detail obtainable by these approaches is illustrated in this short review for selected examples. These include the adsorption of sulfate and other oxyanions, where a crucial role of coadsorbed water is found, the restructuring of Cu electrode surfaces under hydrogen evolution and CO 2 reduction conditions, and the mechanisms of electrochemical Pt oxidation and its correlation with Pt dissolution. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract A compact voltage application setup has been developed for in situ electrical testing of organic field effect transistors in combination with X-ray scattering studies at a synchrotron beamlines. Challenges faced during real condition in-operando test of newly developed OFETs originated an idea of creation of a new setup which excludes number of factors that make experiments complicated. The application of the setup is demonstrated on a prototype of an organic transistors based on α,ω-dihexyl-α-quaterthiophene molecules. The new setup allows to monitor material structural changes by X-ray scattering under applied voltage conditions and their direct correlations. The versatile setup eliminates possible shadowing effects and short circuits due to misalignment of the contacts. The electrical stability of the prototypes was characterized by the application of different voltage values. Corresponding structural changes were monitored by grazing X-ray scattering technique before, during and after the voltage was applied. The selected oligothiophene material with proved transistor properties shows high stability and directional anisotropy under applied voltage conditions. Thanks to a compact and flexible design of the setup, different type of small dimension devices could be studied under external voltage conditions at various synchrotron beamlines. Graphical Abstract

Herein, the concept of constructing binder‐ and carbon additive‐free organosulfur cathode was proved based on thiol‐containing conducting polymer poly(4‐(thiophene‐3‐yl) benzenethiol) (PTBT). The PTBT featured the polythiophene‐structure main chain as a highly conducting framework and the benzenethiol side chain to copolymerize with sulfur and form a crosslinked organosulfur polymer (namely S/PTBT). Meanwhile, it could be in‐situ deposited on the current collector by electro‐polymerization, making it a binder‐free and free‐standing cathode for Li‐S batteries. The S/PTBT cathode exhibited a reversible capacity of around 870 mAh g−1 at 0.1 C and improved cycling performance compared to the physically mixed cathode (namely S&PTBT). This multifunction cathode eliminated the influence of the additives (carbon/binder), making it suitable to be applied as a model electrode for operando analysis. Operando X‐ray imaging revealed the remarkable effect in the suppression of polysulfides shuttle via introducing covalent bonds, paving the way for the study of the intrinsic mechanisms in Li‐S batteries. [ABSTRACT FROM AUTHOR]

A compact voltage application setup has been developed for in situ electrical testing of organic field effect transistors in combination with X-ray scattering studies at a synchrotron beamlines. Challenges faced during real condition in-operando test of newly developed OFETs originated an idea of creation of a new setup which excludes number of factors that make experiments complicated. The application of the setup is demonstrated on a prototype of an organic transistors based on α,ω-dihexyl-α-quaterthiophene molecules. The new setup allows to monitor material structural changes by X-ray scattering under applied voltage conditions and their direct correlations. The versatile setup eliminates possible shadowing effects and short circuits due to misalignment of the contacts. The electrical stability of the prototypes was characterized by the application of different voltage values. Corresponding structural changes were monitored by grazing X-ray scattering technique before, during and after the voltage was applied. The selected oligothiophene material with proved transistor properties shows high stability and directional anisotropy under applied voltage conditions. Thanks to a compact and flexible design of the setup, different type of small dimension devices could be studied under external voltage conditions at various synchrotron beamlines. [ABSTRACT FROM AUTHOR]

Presented here is an electrochemical three-electrode Gas Diffusion Electrode (GDE) cell tailored for operandoand in situ investigations of electrocatalytic processes, with a particular focus on X-ray scattering studies. The optimized cell is engineered to accommodate the minimal sample-detector distances requisite for comprehensive X-ray total scattering investigations. An in-depth understanding of catalytic processes requires their study under 'working' conditions. Configured as a flow-cell, the setup therefore enables the examination of electrocatalysts under high current densities and associated gas evolution phenomena, particularly pertinent for reactions like the oxygen evolution reaction (OER). Notably, its transparency simplifies cell alignment, troubleshooting, and facilitates scans through the catalyst layer, crucial for background corrections. Demonstrating its versatility, we showcase its utility through Small Angle X-ray Scattering (SAXS), X-ray Diffraction (XRD), and X-ray Pair Distribution Function (PDF) analyses of total scattering data., (Copyright 2024 Gustav K. H. Wiberg, Rebecca K. Pittkowski, Stefanie Punke , Olivia Aalling-Frederiksen , Kirsten M. Ø. Jensen, Matthias Arenz. License: This work is licensed under a Creative Commons Attribution 4.0 International License.)

Energy materials form the central part of energy devices. An essential part of their function is the ability to reversibly host charge or energy carriers, and analysis of their phase composition and structure in real time under non-equilibrium conditions is mandatory for a full understanding of their atomic-scale functional mechanism. Real-time powder diffraction is increasingly being applied for this purpose, forming a critical step in the strategic chemical engineering of materials with improved behaviour. This topical review gives examples of real-time analysis using powder diffraction of rechargeable battery electrodes and porous sorbent materials used for the separation and storage of energy-relevant gases to demonstrate advances in the insights which can be gained into their atomic-scale function.

Abstract Through-plane potential and overpotential distributions in a vanadium redox flow battery (VRFB) is investigated in-situ using saturated Ag/AgCl reference electrodes attached to each side of the membrane with edge-type configuration. Combined with electrochemical impedance spectroscopy (EIS), this operando approach enables detailed quantification of the voltage losses contributed from the individual VRFB cell components with the magnitudes of ohmic and charge transfer losses at practical charge-discharge conditions. It is found that the overpotentials for vanadium redox reactions on graphite felt electrodes at the positive and negative half-cells are one order magnitude larger than the voltage loss through the typical cation-exchange membrane (Nafion®117) for charging-discharging at current densities from 50 to 120 mA cm−2. Within the overall half-cell overpotentials, the ohmic voltage loss accounts for about 40%. The analysis reveals that the voltage loss by the anode charge transfer reaction is about three folds larger than that by the cathode reaction, suggesting that sluggish V2+/V3+ redox kinetics in the negative half-cell is the major factor limiting the overall VRFB cell performance. This operando methodology is effective for the in-depth analysis of VRFB performance in practical conditions as well as the development of high-performance cell components and efficient total cell design by a collective and quantitative approach. [ABSTRACT FROM AUTHOR]

Correlations of the through‐plane voltage losses in the vanadium redox flow battery (VRFB), changes in the posolyte (positive electrolyte) and negolyte (negative electrolyte) conditions, energy storage capacity, and coulomb efficiency were investigated under an operando charge–discharge process. Collective and quantitative in situ studies with Ag/AgCl reference‐electrodes inserted into a VRFB single‐cell and the state of charge measuring external open‐circuit voltage half‐cells revealed that the overall performance of a VRFB is predominantly governed by (i) relatively high internal resistance of the anode half‐cell and (ii) conditions of the negolyte as the limiting electrolyte. The studies showed that the round‐trip coulomb efficiency, which is commonly used for VRFB performance analysis, has limitations in expressing the energy storage efficiency and capacity decay phenomena under a consecutive charge–discharge process. In situ and concurrent analysis of the internal cell overpotential and the electrolytes condition can provide quantitative information on the relative contributions of the coulombic round‐trip loss, concentration loss, vanadium crossover, and charge imbalance between the posolyte and negolyte for the overall efficiency and capacity decay phenomena. This operando analysis approach is highly effective for gaining an in‐depth and collective understanding of the complex phenomena taking place in the VRFB system. Operando studies for collective analysis of the internal cell overpotentials and the electrolyte conditions allow for in‐depth understanding of the complex capacity decay phenomena and the performance of vanadium redox flow batteries. [ABSTRACT FROM AUTHOR]

The internal microstructure of a silicon electrode in a lithium ion battery was visualized by operando synchrotron X‐ray radioscopy during battery cycling. The silicon particles were found to change their sizes upon lithiation and delithiation and the changes could be quantified. It was found that volume change of a particle is related to its initial size and is also largely determined by the changing surrounding electron‐conductive network and internal interface chemical environment (e.g. electrolyte migration, solid–electrolyte interphase propagation) within fractured particles. Moreover, an expansion prolongation phenomenon was discovered whereby some particles continue expanding even after switching the battery current direction and shrinkage would be expected, which is explained by assuming different expansion characteristics of particle cores and outer regions. The study provides new basic insights into processes inside Si particles during lithiation and delithiation and also demonstrates the unique possibilities of operando synchrotron X‐ray imaging for studying degradation mechanisms in battery materials. Prolonged expansion: The internal microstructure of a silicon electrode was visualized by operando synchrotron X‐ray radioscopy during battery cycling. A prolongation of expansion was discovered, whereby some particles continued expanding even after switching the battery current direction. [ABSTRACT FROM AUTHOR]

A 20 wt% Co-0.05 wt% Pt/γ-Al2O3 catalyst was investigated to obtain a fundamental understanding of the effect of CO partial pressure (constant H2 partial pressure) on important kinetic parameters of the methanation reaction (x vol% CO/25 vol% H2, x = 3, 5 and 7) by performing advanced transient isotopic and operando diffuse reflectance infrared Fourier transform spectroscopy–mass spectrometry (DRIFTS-MS) experiments. Steady State Isotopic Transient Kinetic Analysis (SSITKA) experiments conducted at 1.2 bar, 230 °C after 5 h in CO/H2 revealed that the surface coverages, θCO and θCHx and the mean residence times, τCO, and τCHx (s) of the reversibly adsorbed CO-s and active CHx-s (Cα) intermediates leading to CH4, respectively, increased with increasing CO partial pressure. On the contrary, the apparent activity (keff, s−1) of CHx-s intermediates, turnover frequency (TOF, s−1) of methanation reaction, and the CH4-selectivity (SCH4, %) were found to decrease. Transient isothermal hydrogenation (TIH) following the SSITKA step-gas switch provided important information regarding the reactivity and concentration of active (Cα) and inactive -CxHy (Cβ) carbonaceous species formed after 5 h in the CO/H2 reaction. The latter Cβ species were readily hydrogenated at 230 °C in 50%H2/Ar. The surface coverage of Cβ was found to vary only slightly with increasing CO partial pressure. Temperature-programmed hydrogenation (TPH) following SSITKA and TIH revealed that other types of inactive carbonaceous species (Cγ) were formed during Fischer-Tropsch Synthesis (FTS) and hydrogenated at elevated temperatures (250–550 °C). The amount of Cγ was found to significantly increase with increasing CO partial pressure. All carbonaceous species hydrogenated during TIH and TPH revealed large differences in their kinetics of hydrogenation with respect to the CO partial pressure in the CO/H2 reaction mixture. Operando DRIFTS-MS transient isothermal hydrogenation of adsorbed CO-s formed after 2 h in 5 vol% CO/25 vol% H2/Ar at 200 °C coupled with kinetic modeling (H-assisted CO hydrogenation) provided information regarding the relative reactivity (keff) for CH4 formation of the two kinds of linear-type adsorbed CO-s on the cobalt surface.

A combination of operando Raman spectroscopy and chronoamperometry was used to examine the carbon tolerance of Sr2Fe1.5Mo0.5O6‐δ (SFMO) electrode catalysts when operating with direct methanol and ethanol fuels in solid oxide fuel cells (SOFCs). Chronoamperometry studies revealed that these devices could maintain a steady power density output under typical SOFC operating conditions. High‐temperature Raman measurements of SFMO coupons exposed to methanol and ethanol (and their gas phase pyrolysis products) showed the presence of spectroscopic features associated with ordered and disordered forms of graphitic carbon. However, once SFMO was employed as an anode in an electrolyte‐supported SOFC, the graphite features disappear implying that these materials are not susceptible to carbon accumulation in functioning devices. These electrochemical and operando Raman measurements provided insight into SFMO's ability to act as an effective anode catalyst for SOFCs operating with direct alcohol fuel sources. Seeing is believing: A combination of operando Raman spectroscopy and electroanalytical measurements are used to explore the ability of Sr2Fe1.5Mo0.5O6‐δ (SFMO) to act as a solid oxide fuel cell (SOFC) anode catalyst in the presence of directly supplied alcohol fuels. The combination of these two analytical techniques reveals that SFMO could resist detrimental graphite formations and provide a steady power density output for the SOFC device with prolonged exposures of these alcohol fuels. [ABSTRACT FROM AUTHOR]

To bring current thermoelectric (TE) materials achievement into a device for power generation, a full understanding of their dynamic behavior under operating conditions is needed. Here, an in operando study is conducted on the high-performance TE material β-Zn4Sb3 under large temperature gradient and thermal cycling via a new approach using in situ transmission electron microscopy combined with characterization of the TE properties. It is found that after 30 thermal cycles in a low-pressure helium atmosphere the TE performance of β-Zn4Sb3 is maintained with the figure of merit, zT, value of 1.4 at 718 K. Under a temperature gradient of 380 K ( Thot = 673 K and Tcold = 293 K) operating for only 30 h, zinc whiskers gradually precipitate on the cold side of the β-Zn4Sb3 leg. The dynamical evolution of Zn in the matrix of β-Zn4Sb3 is found to be the source that leads to a high zT value by lowering of the thermal conductivity and electrical resistivity, but it is also the failure mechanism for the leg under these conditions. The in operando study brings deep insight into the dynamic behavior of nanostructured TE materials for tailoring future TE materials and devices with higher efficiency and longer durability. [ABSTRACT FROM AUTHOR]

To improve lithium and sodium ion battery technology, it is imperative to understand how the properties of the different components are controlled by their chemical structures. Operando structural studies give us some of the most useful information for understanding how batteries work, but it remains difficult to separate out the contributions of the various components of a battery stack (e.g., electrodes, current collectors, electrolyte, and binders) and examine specific materials. We have used operando X-ray diffraction computed tomography (XRD-CT) to study specific components of an essentially unmodified working cell and extract detailed, space-resolved structural information on both crystalline and amorphous phases that are present during cycling by Rietveld and pair distribution function (PDF) methods. We illustrate this method with the first detailed structural examination of the cycling of sodium in a phosphorus anode, revealing surprisingly different mechanisms for sodiation and desodiation in this promising, high-capacity anode system. [ABSTRACT FROM AUTHOR]

Identification of metal cluster catalysis is a topic that is being investigated since a long time. Here, we report a Pd3 metal cluster catalytic reaction investigated by means of operando studies. We discovered that atomically defined tri-nuclear palladium (Pd) is a surprisingly active catalyst for the cycloisomerization of 2-phenylethynylaniline. Operando H NMR spectroscopy and X-ray extended absorption fine structure (EXAFS) measurements have indicated that the structural integrity of such a catalyst remains intact throughout the reaction, which has also been confirmed by an ex situ X-ray photoelectron spectroscopy (XPS) study and catalyst recycling experiments. Kinetic data derived from operando IR spectroscopy measurements have shown that Pd is the active catalytic species. Density functional theory calculations have revealed a reaction pathway consistent with the kinetic data, further supported by NMR titration and X-ray crystal structure studies. Overall, the present study presents a clear example of metal cluster catalysis. [ABSTRACT FROM AUTHOR]

Very high energy X-rays (ca. >40 keV) have long offered great promise in providing great insight into the inner workings of catalysts; insights that may complement the battery of techniques available to researchers in catalysis either in the laboratory or at more conventional X-ray wavelengths. This contribution aims to critically assess the diverse possibilities now available in the high energy domain as a result of the maturation of third generation synchrotron facilities and to look forward to the potential that forthcoming developments in synchrotron source technology may offer the world of catalysis in the near future. [ABSTRACT FROM AUTHOR]

Highlights: [•] WGS reaction mechanism on Pt/Ce1−x Ti x O2−δ was studied by SSITKA-operando methodology. [•] WGS on Pt/Ce0.8Ti0.2O2−δ at 300°C largely follows both the “redox” and “associative formate” mechanisms. [•] CeO2-doped (Zr4+, La3+ and Ti4+) largely affects the concentration of active C-pool and H-pool on Pt/CeO2-doped catalyst. [•] The extent (Δx, nm) of a reactive zone around Pt nanoparticles strongly depends on the dopant. [•] A very good correlation between the active C-pool and the specific WGS reaction rate as a function of dopant exists. [ABSTRACT FROM AUTHOR]

We have developed a new instrumental setup that combines simultaneous X-ray absorption spectroscopy, Raman spectroscopy and online mass spectrometry for operando studies of catalytic reactions. The importance of combining these techniques in the same experiment is demonstrated with the example of CO oxidation over nanoscale copper oxide catalysts supported on high surface area titanium oxide. X-ray absorption near edge structure (XANES) spectroscopy provides information on the charge state and local geometry of the catalytically active atoms. Extended X-ray absorption fine-structure (EXAFS) technique adds information about their local coordination environment. Raman spectroscopy adds sensitivity to crystallographic phase and long range order that both XANES and EXAFS are lacking. Together, these measurements enable simultaneous studies of the structural and electronic properties of all components present in metal-oxide catalysts. Coupled with online reactant and product analysis, this new setup allows one to elucidate the synergy between different components of a catalytic system and shed light on its catalytic activity and selectivity. [ABSTRACT FROM AUTHOR]

Platinum nanoparticles (dPt = 1.0–1.2 nm) supported on single CeO2 and La2O3 metal oxides and Ce0.8La0.2O2−δ solid solution were prepared to investigate for the first time the effect of La3+-doping of ceria on important mechanistic and kinetic aspects of the water-gas shift (WGS) reaction, namely: (i) the concentration and chemical structure of active adsorbed reaction intermediates present in the C-path and H-path of WGS at 250 and 300 °C, () the chemical nature of inactive species formed during WGS, and () the prevailing mechanistic path among “redox” and “associative” both proposed in the literature. For this, steady-state isotopic transient kinetic analysis () experiments coupled with in situ DRIFTS and mass spectrometry were performed to follow the H-path (use of D2O) and C-path (use of 13CO) of the WGS. In addition, other transient isotopic experiments using methodology (use of and mass spectrometry) were designed to follow with time on stream the reactivity toward water of the various adsorbed species formed under WGS. It is proposed that on Pt/Ce1−xLaxO2−δ (x=0.0, 0.2 and 1.0) the WGS reaction follows both the “redox” and “associative” mechanisms but the extent of participation of each mechanism to the overall WGS reaction rate depends on the support chemical composition. The WGS kinetic rate (μmol CO g−1 s−1) increased by a factor of 2.0 and 2.8 at 300 °C on 0.5 wt% Pt supported on Ce0.8La0.2O2−δ compared to CeO2 and La2O3, respectively. This was explained by (i) the larger concentration of active surface intermediates formed around each Pt nanoparticle (larger extent of reactive zone) a(ii) the higher reactivity of sites (k, s−1) responsible for CO2 and H2 formation on Pt/Ce0.8La0.2O2−δ compared to Pt/CeO2 and Pt/La2O3. Active OH groups is suggested to be formed on defect sites (Ce3+□s) of Ce0.8La0.2O2−δ as a consequence of the introduction of La3+ into the ceria lattice, the latter enhancing the concentration of labile oxygen and its surface mobility, important characteristics of the “redox” mechanism. [Copyright &y& Elsevier]

We present the development and performance of a new, reactor-like, in-house ambient pressure X-ray photoelectron spectrometer (AP-XPS) using Al Kα, which can study material surfaces, particularly surfaces of catalysts during catalysis and under reaction conditions. This ambient pressure X-ray photoelectron spectroscopy technique uses an affordable bench-top X-ray source, monochromated Al Kα, making it available for research groups on any campus. A unique feature of this in-house AP-XPS is the integration of a micro ambient pressure reaction cell working in either flowing or batch mode into a monochromatic Al Kα source and an ambient pressure energy analyzer. This integration allows XPS studying surfaces of materials while they functionalize in a flowing gaseous environment. Another feature is the integration of characterization of surfaces of catalysts into simultaneous measurements of catalytic performance by using on-line, quadrupole mass spectrometry and gas chromatography. Performance tests of this in-house AP-XPS have demonstrated that it can study material surfaces at temperatures up to 500-550 °C in a gaseous environment with pressures up to 25-50 Torr. This design has successfully brought the synchrotron-based AP-XPS technique to research groups on campuses. [ABSTRACT FROM AUTHOR]

A detailed kinetic and mechanistic study of the water¿gas shift (WGS) reaction on a 0.5wt% Pt/TiO2 catalyst has been carried out. The dependence of kinetic reaction rate on the partial pressures of reactants (CO, H2O) and products (H2, CO2), and the concentration and chemical structure of active and inactive reaction intermediates that are found in the ¿hydrogen-path¿ and ¿carbon-path¿ of the reaction have been investigated in the 200¿270°C range. The most likely mechanistic pathway of the WGS reaction over the present catalytic system is discussed. It has been found that the reaction rate increases with an increase in the concentration of CO or H2O in the feed stream, while it decreases significantly with the addition of H2 in the feed stream. On the contrary, the kinetic reaction rate was found to be practically independent on the concentration of CO2 in the feed stream. The experimental reaction rates that were estimated were fitted to an empirical power-law rate expression from which the kinetic reaction orders with respect to CO, H2O, CO2, and H2 were estimated to be 0.5, 1.0, ¿0.0, and ¿0.7, respectively. An apparent activation energy of 10.8kcal/mol was also estimated. The formation of formate and carbonate surface species over the TiO2 support under WGS reaction conditions was proved via SSITKA¿DRIFTS experiments. However, these reaction intermediates must be considered as inactive (spectator) species for the steady-state WGS reaction. Additional transient experiments that involved 18O-isotope provided strong support for the red-ox mechanism as the prevailing one on the present Pt/TiO2 catalyst, where labile oxygen and oxygen vacancies of TiO2 near the metal¿support interface can participate in the reaction path of the WGS reaction. [Copyright &y& Elsevier]

The development of in situ techniques and the introduction of operando studies have had a vast impact on research and developments in heterogeneous catalysis. Over the past 40 years, we have gone from a situation where only limited knowledge existed about the state of the active catalyst to a situation where atomic-scale insight about the catalyst and intermediates can routinely be acquired. In fact, it has recently been shown that atomic-resolved images may be obtained in situ for most catalyst systems. Operando studies have shown that catalysts may undergo dynamic structural transformations upon small changes in the reaction conditions and such transformations have a strong impact on the performance of the catalysts. The fact that, strictly speaking, the active state of a catalyst only exists during the catalysis further emphasizes the need for performing operando studies under relevant reaction conditions. The fundamental insight which can be obtained from in situ and operando studies has been important in catalyst developments since it has made more rational catalyst design strategies possible. The progress in in situ characterization and operando studies is illustrated by examples taken mainly from research on hydrodesulfurization and methanol synthesis catalysis. Some of the present major limitations and likely future developments will also be discussed. [Copyright &y& Elsevier]

A 20 wt% Co-0.05 wt% Pt/γ-Al2O3 catalyst was investigated to obtain a fundamental understanding of the effect of CO partial pressure (constant H2 partial pressure) on important kinetic parameters of the methanation reaction (x vol% CO/25 vol% H2, x = 3, 5 and 7) by performing advanced transient isotopic and operando diffuse reflectance infrared Fourier transform spectroscopy–mass spectrometry (DRIFTS-MS) experiments. Steady State Isotopic Transient Kinetic Analysis (SSITKA) experiments conducted at 1.2 bar, 230 °C after 5 h in CO/H2 revealed that the surface coverages, θCO and θCHx and the mean residence times, τCO, and τCHx (s) of the reversibly adsorbed CO-s and active CHx-s (Cα) intermediates leading to CH4, respectively, increased with increasing CO partial pressure. On the contrary, the apparent activity (keff, s−1) of CHx-s intermediates, turnover frequency (TOF, s−1) of methanation reaction, and the CH4-selectivity (SCH4, %) were found to decrease. Transient isothermal hydrogenation (TIH) following the SSITKA step-gas switch provided important information regarding the reactivity and concentration of active (Cα) and inactive -CxHy (Cβ) carbonaceous species formed after 5 h in the CO/H2 reaction. The latter Cβ species were readily hydrogenated at 230 °C in 50%H2/Ar. The surface coverage of Cβ was found to vary only slightly with increasing CO partial pressure. Temperature-programmed hydrogenation (TPH) following SSITKA and TIH revealed that other types of inactive carbonaceous species (Cγ) were formed during Fischer-Tropsch Synthesis (FTS) and hydrogenated at elevated temperatures (250–550 °C). The amount of Cγ was found to significantly increase with increasing CO partial pressure. All carbonaceous species hydrogenated during TIH and TPH revealed large differences in their kinetics of hydrogenation with respect to the CO partial pressure in the CO/H2 reaction mixture. Operando DRIFTS-MS transient isothermal hydrogenation of adsorbed CO-s formed after 2 h in 5 vol% CO/25 vol% H2/Ar at 200 °C coupled with kinetic modeling (H-assisted CO hydrogenation) provided information regarding the relative reactivity (keff) for CH4 formation of the two kinds of linear-type adsorbed CO-s on the cobalt surface. [ABSTRACT FROM AUTHOR]

Na-ion batteries are nowadays receiving renewed attention because of its propitiousness for large-scale stationary applications. Although the Na storage mechanism is still not completely understood, TiO 2 nanoparticles are very promising active anode materials in Na-ion batteries provided that a correct dispersion is achieved within the battery electrode. Whilst the structural changes, either in crystallinity or crystalline phase, that occur during operation are receiving much recent attention, the nanometric morphological evolution of the TiO 2 nanoparticles within the electrode is yet to be thoroughly addressed, despite its implication in battery efficiency. In the present work, operando small-angle x-ray scattering studies on TiO 2 /Na-ion batteries show that whereas the nanoparticle size is preserved during the discharge-charge cycles, the mean distance between nanoparticles increases. The observed morphological changes are consistent with electrode swelling and nanoparticle aggregation during operation, being one phenomenon dominant over the other depending on the applied density current; thus, depending on the differences in ion diffusion within the electrode.

Energy materials form the central part of energy devices. An essential part of their function is the ability to reversibly host charge or energy carriers, and analysis of their phase composition and structure in real time under non-equilibrium conditions is mandatory for a full understanding of their atomic-scale functional mechanism. Real-time powder diffraction is increasingly being applied for this purpose, forming a critical step in the strategic chemical engineering of materials with improved behaviour. This topical review gives examples of real-time analysis using powder diffraction of rechargeable battery electrodes and porous sorbent materials used for the separation and storage of energy-relevant gases to demonstrate advances in the insights which can be gained into their atomic-scale function.

A correction to the article published in the periodical Chemical Communications related to X-ray photoelectron spectroscopy (APXPS ) is presented.