Search

This study reports a facile and reliable operando X‐ray photoelectron spectroscopy (XPS) system for the characterization of the chemical state and electronic structure during Li‐plating/stripping in all‐solid‐state batteries (ASSBs). The measurement conditions (including manufacturing an in situ sample holder) and experimental parameters have been optimized through experimentation. The proposed system accurately defines the status of every metal interlayer component during real‐time battery operation (with simultaneous Li+‐ion in/out migration) under a repeating Li‐plating/stripping process. Moreover, it enables elucidation of ambiguous reaction mechanisms depending on the battery performance, such as the interlayer‐material effect on the efficiency and reversibility of the Li‐plating/stripping process, and changes in the oxygen‐containing bonds due to reaction with Li. The significance of the developed system is further validated by the usefulness and reliability of the valence band structure as a criterion for the analysis of lithium‐metal alloy formation and the progress of de‐alloying reactions. [ABSTRACT FROM AUTHOR]

Metal‐based chalcogenides exhibit great promise for overall water splitting, yet their intrinsic catalytic reaction mechanisms remain to be fully understood. In this work, we employed operando X‐ray absorption (XAS) and in situ Raman spectroscopy to elucidate the structure–activity relationships of low‐crystalline cobalt sulfide (L−CoS) catalysts toward overall water splitting. The operando results for L−CoS catalyzing the alkaline hydrogen evolution reaction (HER) demonstrate that the cobalt centers in the bulk are predominantly coordinated by sulfur atoms, which undergo a kinetic structural rearrangement to generate metallic cobalt in S−Co−Co−S moieties as the true catalytically active species. In comparison, during the acidic HER, L−CoS undergoes local structural optimization of Co centers, and H2 production proceeds with adsorption/desorption of key intermediates atop the Co−S−Co configurations. Further operando characterizations highlight the crucial formation of high‐valent Co4+ species in L−CoS for the alkaline oxygen evolution reaction (OER), and the formation of such active species was found to be far more facile than in crystalline Co3O4 and Co‐LDH references. These insights offer a clear picture of the complexity of active species and site formation in different media, and demonstrate how their restructuring influences the catalytic activity. [ABSTRACT FROM AUTHOR]

Ternary Pd‐In2O3/ZrO2 catalysts exhibit technological potential for CO2‐based methanol synthesis, but developing scalable systems and comprehending complex dynamic behaviors of the active phase, promoter, and carrier are key for achieving high productivity. Here, we show that the structure of Pd‐In2O3/ZrO2 systems prepared by wet impregnation evolves under CO2 hydrogenation conditions into a selective and stable architecture, independent of the order of addition of Pd and In phases on the zirconia carrier. Detailed operando characterization and simulations reveal a rapid restructuring driven by the metal‐metal oxide interaction energetics. The proximity of InPdx alloy particles decorated by InOx layers in the resulting architecture prevents performance losses associated with Pd sintering. The findings highlight the crucial role of reaction‐induced restructuring in complex CO2 hydrogenation catalysts and offer insights into the optimal integration of acid‐base and redox functions for practical implementation. [ABSTRACT FROM AUTHOR]

Mechanochemistry has proven to be an excellent green synthesis method for preparing organic, pharmaceutical, and inorganic materials. Mechanocatalysis, inducing a catalytic reaction by mechanical forces, is an emerging field because neither external temperature nor pressure inputs are required. Previous studies reported enhanced catalytic activity during the mechanical treatment of supported gold catalysts for CO oxidation. So far, the processes inside the milling vessel during mechanocatalysis could not be monitored. In this work, the results of high‐energy operando X‐ray powder diffraction experiments and online gas analysis will be reported. A specific milling setup with a custom‐made vessel and gas dosing system was developed. To prove the feasibility of the experimental setup for operando diffraction studies during mechanocatalysis, the CO oxidation with Au@Fe2O3 as a catalyst was selected as a well‐known model reaction. The operando studies enabled monitoring morphology changes of the support as well as changes in the crystallite size of the gold catalyst. The change of the crystal size is directly correlated to changes in the active surface area and thus to the CO2 yield. The studies confirm the successful implementation of the operando setup, and its potential to be applied to other catalytic reactions. [ABSTRACT FROM AUTHOR]

The copper‐zinc‐alumina (CZA) catalyst is one of the most important catalysts. Nevertheless, understanding of the complex CZA structure is still limited and hampers further optimization. Critical to the production of a highly active and stable catalyst are optimal start‐up procedures in hydrogen. Here, by employing operando X‐ray absorption spectroscopy and X‐ray diffraction, we follow how the industrial CZA precursor evolves into the working catalyst. Two major events in the activation drastically alter the copper‐ and zinc‐containing components in the CZA catalyst and define the final working catalyst structure: the reduction of the starting copper(II) oxide, and the ripening and re‐oxidation of zinc oxide upon the switch to catalytic conditions. These drastic events are also accompanied by other gradual, structural changes. Understanding what happens during these events is key to develop tailored start‐up protocols that are aimed at maximal longevity and activity of the catalysts. [ABSTRACT FROM AUTHOR]

Although a semiconductor gas sensor is promising in the future gas sensing technology, the material design for highly sensitive and selective gas sensing is quite challenging. The crystal plane dependence of gas sensing has been studied using various nano‐crystal samples with a controlled crystal facet to obtain a clue for designing the sensing material, but the contact effect between nano‐crystal particles has often hindered the straightforward analysis. In the present study, the crystal plane dependence of ethanol (EtOH) sensing by ZnO, one of the most widely studied target gas‐sensing material combinations, was investigated from an analytical approach. We applied a newly developed low‐energy He+ ion scattering spectroscopy (He+ LEIS) combined with the pulsed jet technique for analyzing the surface structure of ZnO during the EtOH sensing. In this novel technique, the free gas jet is periodically blown onto the sample surface to simulate the gas‐sensing surface in a vacuum as one under the realistic working condition, while the background pressure is maintained low enough for operating He+ LEIS. It was found that the divalent oxygen adatom on the outermost surface is consumed during the EtOH sensing while no change occurs in the concentration of the lattice oxygen on the Zn‐terminated (0001) surface. The availability of this oxygen adsorbate determines the dissociative EtOH adsorption probability on the surface; hence it determines the EtOH sensing sensitivity, which is substantially higher on Zn‐terminated (0001) than other dominant low‐index surfaces, such as O‐terminated (000 1‾), (10 1‾ 0), and (11 2‾ 0). [ABSTRACT FROM AUTHOR]

Structural dynamics of a Mn‐Na2WO4/SiO2 catalyst were detected directly under reaction conditions during the oxidative coupling of methane via in situ XRD and operando Raman spectroscopy. A new concept of fluctuating storage and release of an active phase in heterogeneous catalysis is proposed that involves the transient generation of active sodium oxide species via a reversible reaction of Na2WO4 with Mn7SiO12. The process is enabled by phase transitions and melting at the high reaction temperatures that are typically applied. [ABSTRACT FROM AUTHOR]

Starvation, flooding, and dry‐out phenomena occur in polymer electrolyte membrane fuel cells (PEMFCs), due to heterogeneous local conditions, material inhomogeneity, and uneven flow distribution across the single cell active area and in between the individual cells. The impact of the load level and air feed conditions on the performance was identified for individual single cells within a 10‐cell stack. Analysis of the current density distribution across the active area at the cell level was correlated with electrochemical impedance spectroscopy to enable operando fault diagnostic without any impact of the applied analytical tools on the single cell behavior. Moreover, the combination of both technologies allows in‐depth analysis of fault mechanisms in fuel cell single cells with improved sensitivity. Current density distribution and the quantitative assessment of the performance homogeneity demonstrated high sensitivity to small humidity changes and allow the detection of critical events, such as dry‐out in single cells. Impedance analysis is more sensitive regarding polarization and diffusion limitations and allows detection of cell flooding. The combination of both techniques is required for reliable identification of air starvation faults. [ABSTRACT FROM AUTHOR]

Operando analyses have provided several breakthroughs in the construction of high‐performance materials and devices, including energy storage systems. However, despite the advances in electrode engineering, the formidable issues of lithium intercalation and deintercalation kinetics cannot be investigated by using planar observations. This study concerns side‐view operando observation by optical microscopy of a graphite anode based on its color changes during electrochemical lithiation. Since the graphite color varies according to the optical energy gap during lithiation and delithiation, this technique can be used to study the corresponding charge–discharge kinetics. In addition, the cell configuration uses liquid electrolytes similar to commercial cells, allowing practical application. Furthermore, this side‐view observation has shown that microscale spatial variations in rate and composition control the insertion and deinsertion, revealing the kinetics throughout the whole electrode. The results of this study could enhance the fundamental understanding of the kinetics of battery materials. [ABSTRACT FROM AUTHOR]

It is generally believed that CO2 electroreduction to multi‐carbon products such as ethanol or ethylene may be catalyzed with significant yield only on metallic copper surfaces, implying large ensembles of copper atoms. Here, we report on an inexpensive Cu‐N‐C material prepared via a simple pyrolytic route that exclusively feature single copper atoms with a CuN4 coordination environment, atomically dispersed in a nitrogen‐doped conductive carbon matrix. This material achieves aqueous CO2 electroreduction to ethanol at a Faradaic yield of 55 % under optimized conditions (electrolyte: 0.1 m CsHCO3, potential: −1.2 V vs. RHE and gas‐phase recycling set up), as well as CO electroreduction to C2‐products (ethanol and ethylene) with a Faradaic yield of 80 %. During electrolysis the isolated sites transiently convert into metallic copper nanoparticles, as shown by operando XAS analysis, which are likely to be the catalytically active species. Remarkably, this process is reversible and the initial material is recovered intact after electrolysis. [ABSTRACT FROM AUTHOR]

Three‐dimensional imaging using X‐ray as a probe is state‐of‐the‐art for the characterization of heterogeneous materials. In addition to simple imaging of sample morphology, imaging of elemental distribution and chemical states provides advanced maps of key structural parameters of functional materials. The combination of X‐ray absorption fine structure (XAFS) spectroscopy and three‐dimensional imaging such as computed tomography (CT) can visualize the three‐dimensional distribution of target elements, their valence states, and local structures in a non‐destructive manner. In this personal account, our recent results on the three‐dimensional XAFS imaging for Pt cathode catalysts in the membrane electrode assembly (MEA) of polymer electrolyte fuel cell (PEFC) are introduced. The distribution and chemical states of Pt cathode catalysts in MEAs remarkably change under PEFC operating conditions, and the 3D XAFS imaging revealed essential events in PEFC MEAs. [ABSTRACT FROM AUTHOR]

Latest advances on operando analysis in the field of next‐generation battery research are highlighted by means of three examples: recording the pressure change and performing X‐ray diffraction analysis of metal‐oxygen batteries allows to gain detailed understanding of the main reactions and side reactions; analyzing a solid electrolyte in a hot‐press setup allows to monitor crystallization and stability during its synthesis. Since batteries are (electro)chemical reactors, the benefit of using the introduced operando techniques for classical reaction engineering is highlighted thereof. [ABSTRACT FROM AUTHOR]

Developing scalable systems and understanding dynamic behaviors are crucial for advancing the technological potential of multicomponent catalysts for CO2‐based methanol synthesis. In their Research Article (e202306563), Javier Pérez‐Ramírez and co‐workers show that the reaction‐induced restructuring of Pd‐In2O3/ZrO2 systems, prepared via impregnation, leads to a unique architecture that integrates the necessary acid‐base functionality of In2O3 with the H2 splitting ability of an InPd2 alloy, while also ensuring high stability. [ABSTRACT FROM AUTHOR]

To investigate how exhaust heat from automobiles can be converted to renewable energy, an innovative electrothermodynamic cycle is presented, which is based on temporal temperature variations, the pyroelectric effect, instead of spatial temperature gradient, and the Seebeck effect. A generating mechanism is investigated using operando time‐resolved synchrotron X‐ray diffraction. Practical energy and true energy breakeven are achieved via real engine dynamometer experiments. [ABSTRACT FROM AUTHOR]

By using operando Raman spectroscopy (ORS), we investigated the panoramic structure evolution of an iron oxide (α-Fe2O3) catalyst, which is used for the production of olefins via Fischer-Tropsch (FTO). During activation in different atmospheres and reaction at 260 °C and 3.0 MPa, α-Fe2O3 was only partially transformed into γ-Fe2O3 by H2 pretreatment; meanwhile, a transformation of α-Fe2O3→γ-Fe2O3→Fe3O4→Fe5C2 was observed in both CO and syngas (H2/CO). Combining with other techniques such as XRD, TEM, XPS and TPSR, we reveal that assembles of various iron oxides (γ-Fe2O3, Fe3O4, Fe carbide, and their combinations) are responsible for FTO. Especially, the preliminary relationship of catalyst structure and performance relating to the production of olefins directly from syngas was established. Such a study is critical for further understanding of the FTO reaction and other catalytic reactions. [ABSTRACT FROM AUTHOR]

Keywords: Activation; CO2 Conversion; Copper; operando Analysis; Zinc EN Activation CO2 Conversion Copper operando Analysis Zinc 1 1 1 03/30/22 20220404 NES 220404 B Copper and zinc oxide b are a dream team in transforming carbon dioxide and carbon monoxide together with hydrogen into the valuable base chemical methanol. Inspired by the cover art of the music masterpiece "Wish you were here" by Pink Floyd, the picture featuring the Research Article (e202200301) by Jeroen A. van Bokhoven and co-workers highlights the fundamental collaboration of the copper and zinc oxide phase in methanol catalysts for a sustainable future. Inside Cover: Drastic Events and Gradual Change Define the Structure of an Active Copper-Zinc-Alumina Catalyst for Methanol Synthesis (Angew. [Extracted from the article]

How can we convert exhaust heat from automobiles to renewable energy? In article number 1401942 Yoonho Kim, Hirohisa Tanaka, and co‐workers present an innovative electro‐thermodynamic cycle as an answer. The cycle is based on temporal temperature variations, the pyroelectric effect (instead of spatial temperature gradient), and the Seebeck effect, and the mechanism is investigated using operando time‐resolved synchrotron X‐ray diffraction. Practical energy and true energy breakeven are first achieved through real engine dynamometer experiments. Cover image by Remi Tanaka. [ABSTRACT FROM AUTHOR]

The cover picture shows that the relationship between the structure and performance of industrial catalysts can be established by using high‐pressure‐operando Raman spectroscopy (HPORS). In their Communication, D. Fu et al. use HPORS to study the origin of active sites for the iron‐based Fischer–Tropsch to olefins reaction by observing the phase transformation during different activation processes. This methodology could be extended to other types of industrial catalysts, such as MnOx , MoOx /MoS2 , CrOx , and zeolites. The article highlighted by this cover can be found on p. 752 ff. of Issue 5, 2015. [ABSTRACT FROM AUTHOR]