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This perspective outlines recent developments in the field of NMR spectroscopy, enabling new opportunities for in situ studies on bulk and confined clathrate hydrates. These hydrates are crystalline ice-like materials, built up from hydrogen-bonded water molecules, forming cages occluding non-polar gaseous guest molecules, including CH4, CO2 and even H2 and He gas. In nature, they are found in low-temperature and high-pressure conditions. Synthetic confined versions hold immense potential for energy storage and transportation, as well as for carbon capture and storage. Using previous studies, this report highlights static and magic angle spinning NMR hardware and strategies enabling the study of clathrate hydrate formation in situ, in bulk and in nano-confinement. The information obtained from such studies includes phase identification, dynamics, gas exchange processes, mechanistic studies and the molecular-level elucidation of the interactions between water, guest molecules and confining interfaces. [ABSTRACT FROM AUTHOR]

The formation of carbon deposits is a major deactivation pathway for solid catalysts. Studying coking on industrially relevant catalysts is, however, often challenging due to the sample heterogeneity. That is especially true for zeolite‐containing catalysts where fluorescence often hampers their characterization with Raman spectroscopy. We turned this disadvantage into an advantage and combined Raman and fluorescence (lifetime) microscopy to study the coking behavior of an equilibrium catalyst material used for fluid catalytic cracking of hydrocarbons. The results presented illustrate that this approach can yield new insights in the physicochemical processes occurring within zeolite‐containing catalyst particles during their coking process. Ex situ analyses of single catalyst particles revealed considerable intra‐sample heterogeneities. The sample‐averaged Raman spectra showed a higher degree of graphitization when the sample was exposed to more hexane, while the sample‐averaged fluorescence lifetime showed no significant trend. Simultaneous in situ Raman and fluorescence (lifetime) microscopy, used to follow the coking and the regeneration of single particles, gave more insights in the changing fluorescence dynamics. During the coking, the rise and decline of the average fluorescence lifetime suggested the prolonged presence of smaller coke species that are quenched more and more by adjacent larger polyaromatics acting as Förster‐resonance‐energy‐transfer acceptors. [ABSTRACT FROM AUTHOR]

The stability of Zinc metal anodes (ZMAs) significantly limits the electrochemical performance and practical application of aqueous Zn‐ion batteries (ZIBs). An efficient and economical solution is the use of trace additives. However, efforts on trace additives are sparse, and essential uncertainties remain concerning their role in the stabilization of ZMAs. Herein, a low‐cost ZnSO4‐based aqueous electrolyte containing trace amounts of Acesulfame‐K (AK) (only 1.0 mg mL−1) is reported, which effectively suppresses the parasitic reactions occurring on the ZMA surface to realize a dendrite‐free Zn2+ deposition process, an ultra‐long cycle life over 1600 h and a high Coulombic efficiency of 99.86%. Accordingly, the practical Zn//NH4V4O10 full cell with AK also exhibits a high discharge capacity and capacity retention. In situ spectroscopies coupled with theoretical calculations reveal that the trace AK tends to accumulate at the ZMA/electrolyte interface to alleviate electrolyte corrosion. More importantly, the adsorbed AK can regulate the interfacial H2O structures (i.e., disrupting the interfacial H‐bonds to form more isolated H2O) to reduce the proton/hydroxides transport, thus suppressing the parasitic hydrogen evolution reaction and improving low‐temperature acclimation. This study provides design inspiration for trace additives expected to enable low‐cost and practical ZIBs with long lifespans. [ABSTRACT FROM AUTHOR]

Spectroelectrochemistry, especially ATR‐SEIRAS, is an emerging method to identify key descriptors for optimizing reaction systems in organic electrosynthesis. Here, the upgrading of biogenic acids via Kolbe electrolysis and reductive transformations was studied. The findings affirm acid group adsorption on electrodes, consistent with existing literature. The effectiveness of Kolbe reaction in suppressing the parasitic ethanol oxidation reaction was observed, whereas it faces stiff competition from the methanol oxidation reaction. Parallel reduction and reductive amination of levulinic acid were uncovered, both relying on adsorbed organic species rather than molecular H2. Intriguingly, the electrode's polarization influences the bond strength, enabling discrimination between acid and ketone species within levulinic acid. [ABSTRACT FROM AUTHOR]

In this work, we present a recent advancement in high‐temperature instrumentation in the form of a heating stage that enables studies to be performed in the temperature range of 20–1250°C under high‐vacuum, millibar, and atmospheric pressure conditions (10−7–1000 mbar). The newly developed laser‐based heating solution is described in detail. Its functionality is highlighted in this study in the form of a heating stage compatible with in situ ambient pressure X‐ray photoelectron spectroscopy (APXPS). The proof‐of‐concept experiment presented in this work involves a polycrystalline nickel foil, a material of considerable interest in the scientific field due to its applications in catalysis, batteries, and electrochemistry. Owing to the intrinsic oxophilicity of nickel, the experiment targeted the high‐temperature oxidation (600°C) and reduction (1050°C) that serves interest as both, a pretreatment and preparation method, and as a model reaction for the redox behavior of non‐noble materials under reactive conditions. Complete and reversible surface state changes from metallic to oxide and back to metallic were achieved through stepwise variations of the gas phase composition and temperature. The heating stage showed high stability at high temperatures under reducing and oxidizing conditions, demonstrating the benefit of this design. The in situ characterization possibilities enabled by this stage will allow a better understanding of the inherent properties of materials that function at high temperatures, leading to their optimization in relevant application fields such as catalysis, materials, and surface science. [ABSTRACT FROM AUTHOR]

Electrochemical NO2−-to-NH3 conversion (NO2RR) offers a green route to NH3 electrosynthesis, while developing efficient NO2RR catalysis systems at high current densities remains a grand challenge. Herein, we report an efficient Zr-NiO catalyst with atomically dispersed Zr-dopants incorporated in NiO lattice, delivering the exceptional NO2RR performance with industrial-level current density (>0.2 A cm−2). In situ spectroscopic measurements and theoretical simulations reveal the construction of Zr-Ni frustrated Lewis acid-base pairs (FLPs) on Zr-NiO, which can substantially increase the number of absorbed nitrite (NO2−), promote the activation and protonation of NO2− and concurrently hamper the H coverage, boosting the activity and selectivity of Zr-NiO towards the NO2RR. Remarkably, Zr-NiO exhibits the exceptional performance in a flow cell with high Faradaic efficiency for NH3 of 94.0% and NH3 yield rate of 1,394.1 µmol h−1 cm−2 at an industrial-level current density of 228.2 mA cm−2, placing it among the best NO2RR electrocatalysts for NH3 production. [ABSTRACT FROM AUTHOR]

Phospholane-phosphites are known to show highly unusual selectivity towards branched aldehydes in the hydroformylation of terminal alkenes. This paper describes the synthesis of hitherto unknown unsaturated phospholene borane precursors and their conversion to the corresponding phospholene-phosphites. The relative stereochemistry of one of these ligands and its Pd complex was assigned with the aid of X-ray crystal structure determinations. These ligands were able to approach the level of selectivity observed for phospholane-phosphites in the rhodium-catalysed hydroformylation of propene. High-pressure infra-red (HPIR) spectroscopic monitoring of the catalyst formation revealed that whilst the catalysts showed good thermal stability with respect to fragmentation, the C=C bond in the phospholene moiety was slowly hydrogenated in the presence of rhodium and syngas. The ability of this spectroscopic tool to detect even subtle changes in structure, remotely from the carbonyl ligands, underlines the usefulness of HPIR spectroscopy in hydroformylation catalyst development. [ABSTRACT FROM AUTHOR]

Surfactants are widely used in the synthesis of nanoparticles, as they have a remarkable ability to direct their growth to obtain well-defined shapes and sizes. However, their post-synthesis removal is a challenge, and the methods used often result in morphological changes that defeat the purpose of the initial controlled growth. Moreover, after the removal of surfactants, the highly active surfaces of nanomaterials may undergo structural reconstruction by exposure to a different environment. Thus, ex situ characterization after air exposure may not reflect the effect of the cleaning methods. Here, combining X-ray photoelectron spectroscopy, in situ infrared reflection absorption spectroscopy, and environmental transmission electron microscopy measurements with CO probe experiments, we investigated different surfactant-removal methods to produce clean metallic Pt nanoparticles from surfactant-encapsulated ones. It was demonstrated that both ultraviolet-ozone (UV-ozone) treatment and room temperature O2 plasma treatment led to the formation of Pt oxides on the surface after the removal of the surfactant. On the other hand, when H2 was used for plasma treatment, both the Pt0 oxidation state and nanoparticle size distribution were preserved. In addition, H2 plasma treatment can reduce Pt oxides after O2-based treatments, resulting in metallic nanoparticles with clean surfaces. These findings provide a better understanding of the various options for surfactant removal from metal nanoparticles and point toward non-thermal plasmas as the best route if the integrity of the nanoparticle needs to be preserved. [ABSTRACT FROM AUTHOR]

The aprotic lithium‐oxygen (Li‐O2) battery has an extremely high theoretical specific energy and potentially provides a tantalizing solution to the renewable energy storage challenge encountered by contemporary and future societies. Nevertheless, the realization of practical Li‐O2 batteries currently meets with substantial challenges that include, but are not limited to, low energy capability and short longevity. To address these obstacles, unveiling the reaction processes and degradation mechanisms of Li‐O2 batteries is crucially important. Over recent years, the research paradigm of in situ spectroscopy coupled with theoretical calculations performed on well‐designed model interfaces, has proved to be indispensable for the fundamental study and performance optimization of various energy storage devices. In this contribution, first representative illustrations of this research paradigm are offered in the study of both primary and parasitic reactions of Li‐O2 batteries, which significantly simplifies, but not degrade, the complex reaction conditions and decouples multiple processes occurring simultaneously in Li‐O2 cells. Then, the perspective is provided on the remaining issues as well as uncertainties and discuss future research directions. Finally, wider research community is encouraged to tailor‐design versatile model interfaces to better bridge in situ spectroscopy and theoretical calculations for the research and development of better Li‐O2 batteries and beyond. [ABSTRACT FROM AUTHOR]

This perspective outlines recent developments in the field of NMR spectroscopy, enabling new opportunities for in situ studies on bulk and confined clathrate hydrates. These hydrates are crystalline ice-like materials, built up from hydrogen-bonded water molecules, forming cages occluding non-polar gaseous guest molecules, including CH4, CO2 and even H2 and He gas. In nature, they are found in low-temperature and high-pressure conditions. Synthetic confined versions hold immense potential for energy storage and transportation, as well as for carbon capture and storage. Using previous studies, this report highlights static and magic angle spinning NMR hardware and strategies enabling the study of clathrate hydrate formation in situ, in bulk and in nano-confinement. The information obtained from such studies includes phase identification, dynamics, gas exchange processes, mechanistic studies and the molecular-level elucidation of the interactions between water, guest molecules and confining interfaces.

Understanding the dynamic structural evolution of supported metal clusters under reaction conditions is crucial to develop structure reactivity relations. Here, we followed the structure of different size Rh clusters supported on Al2O3 using in situ/operando spectroscopy and ex situ aberration‐corrected electron microscopy. We report a dynamic evolution of rhodium clusters into thermally stable isolated single atoms upon exposure to oxygen and during CO oxidation. Rh clusters partially disperse into single atoms at room temperature and the extent of dispersion increases as the Rh size decreases and as the reaction temperature increases. A strong correlation is found between the extent of dispersion and the CO oxidation kinetics. More importantly, dispersing Rh clusters into single atoms increases the activity at room temperature by more than two orders of magnitude due to the much lower activation energy on single atoms (40 vs. 130 kJ/mol). This work demonstrates that the structure and reactivity of small Rh clusters are very sensitive to the reaction environment. [ABSTRACT FROM AUTHOR]

Water‐induced parasitic reaction, e.g., spontaneous corrosion and hydrogen evolution reaction, has been widely recognized as a culprit of the poor electrochemical performance of Zn anode in aqueous electrolyte. Nevertheless, how the interfacial water, the pertinent participant of the Zn electrochemistry, affects the parasitic reaction occurring on Zn anode remains incompletely understood. Herein, a step forward toward understanding the relationship of the hydrogen‐bond network of interfacial water and the electrochemical performance of Zn anode is reported, where the structure of interfacial water can be regulated by (aminomethyl)phosphonic acid (AMPA), a molecular additive that can specifically adsorb on Zn surface. Direct spectral evidence coupled with theoretical calculation reveals that the AMPA preferentially adsorbs on the Zn anode surface that serves as a shield for water dissociation (i.e., spontaneous corrosion). Moreover, AMPA can promote interfacial water toward ordered H‐bond network with high electrochemical stability at electrified interface. As a result, water‐induced parasitic reaction has been significantly suppressed, enabling a dendrite‐free Zn2+ deposition, an exceptional high coulombic efficiency, prolonged longevity of model Zn/Zn cells, and improved Zn//NH4V4O10 full battery. The results presented here underscore the ramifications of interfacial water structure and provide design criteria for versatile electrolytes of rechargeable Zn batteries. [ABSTRACT FROM AUTHOR]

The interaction between metal particles and the oxide support, the so-called metal–support interaction, plays a critical role in the performance of heterogenous catalysts. Probing the dynamic evolution of these interactions under reactive gas atmospheres is crucial to comprehending the structure–performance relationship and eventually designing new catalysts with enhanced properties. Cobalt supported on TiO2 (Co/TiO2) is an industrially relevant catalyst applied in Fischer−Tropsch synthesis. Although it is widely acknowledged that Co/TiO2 is restructured during the reaction process, little is known about the impact of the specific gas phase environment at the material's surface. The combination of soft and hard X-ray photoemission spectroscopies are used to investigate in situ Co particles supported on pure and NaBH4-modified TiO2 under H2, O2, and CO2:H2 gas atmospheres. The combination of soft and hard X-ray photoemission methods, which allows for simultaneous probing of the chemical composition of surface and subsurface layers, is one of the study's unique features. It is shown that under H2, cobalt particles are encapsulated below a stoichiometric TiO2 layer. This arrangement is preserved under CO2 hydrogenation conditions (i.e., CO2:H2), but changes rapidly upon exposure to O2. The pretreatment of the TiO2 support with NaBH4 affects the surface mobility and prevents TiO2 spillover onto Co particles. [ABSTRACT FROM AUTHOR]

In this work, we explored the in-situ reaction modeling of the molecular self-aggregation of methylene blue (MB), which is a cationic thiazine dye, in different solvents via a container-less acoustic levitator by floating of a single droplet. Our in-situ spectroscopic study revealed that the dimer essentially has a sandwich structural geometry with a deviation from parallel stacking and horizontal arrangements in the molecular planes. The real time conversion of the monomer in MB into a dimer and their dynamics in water and ethanol media were monitored using a free-standing acoustic levitator droplet system. The absorption spectra revealed changes in the two resolved peaks (monomer and dimer) and orderliness when water and ethanol were used as the media. Interestingly, the enhancement in the dimerization of MB could be attributed to droplet evaporation, which is difficult to observe in typical reactor containers. Moreover, acidic protonation resulted in a change in the aggregation orientation direction of the MB molecules, forming an unusual J-aggregation. Theoretical DFT calculations revealed that MB underwent typical H-aggregation and J-aggregation in the different solvent environments, and their orientations well matched the spectroscopic data.

The solid electrolyte interphase (SEI) on lithium metal anodes (LMA) plays a critical role in affording a long lifespan required for aprotic lithium‐oxygen (Li–O2) batteries. Nevertheless, the crossover of oxygen from the cathode to the anode, an inevitable phenomenon for most of the current Li–O2 batteries, and its effects on the formation and operation of SEI on LMA remain less explored. In this work, a mechanistic study of the SEI formation at a model Cu/dimethyl sulfoxide (DMSO) interface in the presence of oxygen is presented. Direct spectroscopic evidence coupled with theoretical calculation reveals that oxygen can alter the SEI formation pathway and result in distinct SEI properties. Specifically, oxygen can inhibit the fission of the C–S bond of DMSO solvent and therefore reduce the formation of unstable SEI components (e.g., C≡C species) and volatile products (e.g., C2H6 and H2). Thus, the SEI formed under oxygen is more uniform and of less voids, and enables improved electrochemical performance of LMA. This work presents new insights into the oxygen crossover effects on SEI chemistry and is beneficial for designing better LMA/electrolyte interface for future Li–O2 batteries. [ABSTRACT FROM AUTHOR]

Room‐temperature ionic liquids (ILs) have gained considerable attention as an important addition to conventional electrolytes because they exhibit large electrochemical windows and can reduce existing overpotentials in electrocatalysis. For the interfacial electrochemistry of ILs, a comprehensive understanding of molecular ions and the resulting electric double‐layer structures as a function of electrode potential is mandatory, but the structures are largely different from conventional electrolytes. For that reason, we have studied the interfaces of Pt(111) in contact with ILs using 1‐butyl‐3‐methylimidazolium [BMIM] and 1‐butyl‐2,3‐dimethylimidazolium [BMMIM] cations as well as bis(trifluoromethylsulfonyl)imide [NTf2] anions. We applied vibrational sum‐frequency generation (SFG), where we interrogate vibrational bands from interfacial cations, anions, as well as interfacial water in situ and under potential control. Structuring of [NTf2] anions and H2O with electrode potential show hysteresis while a strong Stark tuning was absent. This indicates that the IL ions are oriented in the vicinity of the interface, without being directly adsorbed to the Pt(111) surface. Using the C‐H stretching band from CH groups at the imidazolium ring, the ring reorientation with electrode potential was qualitatively determined. The imidazolium ring reorients as a function of potential from a more parallel orientation to an upright orientation with respect to the interfacial plane. This leads to the formation of voids in the layered structure of ions at the interface, which can be then filled with H2O as evidenced by an increased SFG intensity from O‐H stretching modes that are attributable to hydrogen‐bonded interfacial water. Comparing the responses of the ILs, particularly of [BMMIM][NTf2], shows a compact structure and a significantly pronounced rearrangement of the imidazolium ring that can also facilitates better incorporation of H2O and significantly affects the reorientation of [NTf2] anions and, thus, causes a pronounced hysteresis with electrode potential. [ABSTRACT FROM AUTHOR]

The ability to tailor oxide heterointerfaces has led to novel properties in low-dimensional oxide systems. A fundamental understanding of these properties is based on the concept of electronic charge transfer. However, the electronic properties of oxide heterointerfaces crucially depend on their ionic constitution and defect structure: ionic charges contribute to charge transfer and screening at oxide interfaces, triggering a thermodynamic balance of ionic and electronic structures. Quantitative understanding of the electronic and ionic roles regarding charge-transfer phenomena poses a central challenge. Here, the electronic and ionic structure is simultaneously investigated at the prototypical charge-transfer heterointerface, LaAlO3 /SrTiO3 . Applying in situ photoemission spectroscopy under oxygen ambient, ionic and electronic charge transfer is deconvoluted in response to the oxygen atmosphere at elevated temperatures. In this way, both the rich and variable chemistry of complex oxides and the associated electronic properties are equally embraced. The interfacial electron gas is depleted through an ionic rearrangement in the strontium cation sublattice when oxygen is applied, resulting in an inverse and reversible balance between cation vacancies and electrons, while the mobility of ionic species is found to be considerably enhanced as compared to the bulk. Triggered by these ionic phenomena, the electronic transport and magnetic signature of the heterointerface are significantly altered.

Phospholane-phosphites are known to show highly unusual selectivity towards branched aldehydes in the hydroformylation of terminal alkenes. This paper describes the synthesis of hitherto unknown unsaturated phospholene borane precursors and their conversion to the corresponding phospholene-phosphites. The relative stereochemistry of one of these ligands and its Pd complex was assigned with the aid of X-ray crystal structure determinations. These ligands were able to approach the level of selectivity observed for phospholane-phosphites in the rhodium-catalysed hydroformylation of propene. High-pressure infra-red (HPIR) spectroscopic monitoring of the catalyst formation revealed that whilst the catalysts showed good thermal stability with respect to fragmentation, the C=C bond in the phospholene moiety was slowly hydrogenated in the presence of rhodium and syngas. The ability of this spectroscopic tool to detect even subtle changes in structure, remotely from the carbonyl ligands, underlines the usefulness of HPIR spectroscopy in hydroformylation catalyst development.

Surfactants are widely used in the synthesis of nanoparticles, as they have a remarkable ability to direct their growth to obtain well-defined shapes and sizes. However, their post-synthesis removal is a challenge, and the methods used often result in morphological changes that defeat the purpose of the initial controlled growth. Moreover, after the removal of surfactants, the highly active surfaces of nanomaterials may undergo structural reconstruction by exposure to a different environment. Thus, ex situ characterization after air exposure may not reflect the effect of the cleaning methods. Here, combining X-ray photoelectron spectroscopy, in situ infrared reflection absorption spectroscopy, and environmental transmission electron microscopy measurements with CO probe experiments, we investigated different surfactant-removal methods to produce clean metallic Pt nanoparticles from surfactant-encapsulated ones. It was demonstrated that both ultraviolet-ozone (UV-ozone) treatment and room temperature O2 plasma treatment led to the formation of Pt oxides on the surface after the removal of the surfactant. On the other hand, when H2 was used for plasma treatment, both the Pt0 oxidation state and nanoparticle size distribution were preserved. In addition, H2 plasma treatment can reduce Pt oxides after O2-based treatments, resulting in metallic nanoparticles with clean surfaces. These findings provide a better understanding of the various options for surfactant removal from metal nanoparticles and point toward non-thermal plasmas as the best route if the integrity of the nanoparticle needs to be preserved.

Abstract Room‐temperature ionic liquids (ILs) have gained considerable attention as an important addition to conventional electrolytes because they exhibit large electrochemical windows and can reduce existing overpotentials in electrocatalysis. For the interfacial electrochemistry of ILs, a comprehensive understanding of molecular ions and the resulting electric double‐layer structures as a function of electrode potential is mandatory, but the structures are largely different from conventional electrolytes. For that reason, we have studied the interfaces of Pt(111) in contact with ILs using 1‐butyl‐3‐methylimidazolium [BMIM] and 1‐butyl‐2,3‐dimethylimidazolium [BMMIM] cations as well as bis(trifluoromethylsulfonyl)imide [NTf2] anions. We applied vibrational sum‐frequency generation (SFG), where we interrogate vibrational bands from interfacial cations, anions, as well as interfacial water in situ and under potential control. Structuring of [NTf2] anions and H2O with electrode potential show hysteresis while a strong Stark tuning was absent. This indicates that the IL ions are oriented in the vicinity of the interface, without being directly adsorbed to the Pt(111) surface. Using the C‐H stretching band from CH groups at the imidazolium ring, the ring reorientation with electrode potential was qualitatively determined. The imidazolium ring reorients as a function of potential from a more parallel orientation to an upright orientation with respect to the interfacial plane. This leads to the formation of voids in the layered structure of ions at the interface, which can be then filled with H2O as evidenced by an increased SFG intensity from O‐H stretching modes that are attributable to hydrogen‐bonded interfacial water. Comparing the responses of the ILs, particularly of [BMMIM][NTf2], shows a compact structure and a significantly pronounced rearrangement of the imidazolium ring that can also facilitates better incorporation of H2O and significantly affects the reorientation of [NTf2] anions and, thus, causes a pronounced hysteresis with electrode potential.

The Mars Multispectral Imager for Subsurface Studies (Ma_MISS) instrument is a miniaturized visible and near-infrared spectrometer that is integrated into the drilling system of the ESA Rosalind Franklin rover, which is devoted to subsurface exploration on Mars. Ma_MISS will acquire spectral data on the Martian subsurface from excavated borehole walls. The spectral data collected by Ma_MISS on unexposed rocks will be crucial for determination of the composition of subsurface rocks and optical and physical properties of materials (i.e., grain size). Ma_MISS will further contribute to a reconstruction of the stratigraphic column and acquire data on subsurface geological processes. Ma_MISS data may also inform with regard to the presence of potential biomarkers in the subsurface, given the presence of organic matter that may affect some spectral parameters. In this framework, we performed a wide range of measurements using the laboratory model of the Ma_MISS to investigate mineral/organic mixtures in different proportions. We prepared mixtures by combining kaolinite and nontronite with glycine, asphaltite, polyoxymethylene, and benzoic acid. These organic compounds show different spectral characteristics in the visible and near-infrared; therefore their presence can be detected by the Ma_MISS instrument. Our results indicate that the Ma_MISS instrument can detect organic material down to abundances of around 1 wt %. In particular, the data collected on low-concentration mixtures show that, by analyzing sediments with a grain size smaller than the Ma_MISS spatial resolution, the instrument can still discern those points where organic matter is present from points with exclusive mineral composition. The results also show that a collection of multiple contiguous measurements on a hypothetical borehole wall could help indicate the presence of organic matter in clay-rich soils if present. [ABSTRACT FROM AUTHOR]

Teotihuacan, the main city of the Classic period in Central Mexico (ca. 150/200–650 CE), was among many things, a colorful city. Through its application on mural painting, ceramics, lapidary, bone, textiles, and the human body itself, coloring materials gave meaning to the Teotihuacan reality. This research presents color as a socio-technological phenomenon from the archaeology of color, the anthropology of technology, and the application of the concept of technological style. From this scope, pictorial palettes of mural painting fragments from three Teotihuacan architectural compounds were studied by digital microscopy, colorimetry, fiber optic reflectance spectroscopy (FORS), X-ray fluorescence (XRF), Raman spectroscopy, infrared spectroscopy (FTIR), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) in order to identify the color technology of pigments. This approach led us to identify materials shared by the three studied compounds, red and yellow earths, cinnabar, malachite, pseudomalachite, azurite, and the Teotihuacan grayish blue, found to contain a mix of bone black with calcite. Our results contribute to the discussion on the use of raw materials and their mixtures. We observed a standardization of pigment technology in Teotihuacan mural painting through the use of shared and standard formulations with four indicators that we propose as markers of a technological style for pigments, along with variations in the color materials that evidence the use of different strategies for the procurement and distribution of raw materials among the diverse architectural assemblages of the city. [ABSTRACT FROM AUTHOR]

The surface structure of oxide‐supported metal nanoparticles can be determined via characteristic vibrations of adsorbed probe molecules such as CO. Usually, spectroscopic studies focus on peak position and intensity, which are related to binding geometries and number of adsorption sites, respectively. Employing two differently prepared model catalysts, it is demonstrated that polarization‐dependent sum‐frequency‐generation (SFG) spectroscopy reveals the average surface structure and shape of the nanoparticles. SFG results for different particle sizes and morphologies are compared to direct real‐space structure analysis by TEM and STM. The described feature of SFG could be used to monitor particle restructuring in situ and may be a valuable tool for operando catalysis. [ABSTRACT FROM AUTHOR]

Advanced in situ X‐ray absorption spectroscopy characterization of electrochemically co‐electrodeposited bi‐element copper alloy electrodes shows that zinc yields the formation of a stable cationic Cu species during the electroreduction of CO2 at high cathodic polarization. In contrast, the formation/stabilization of cationic Cu species in copper oxides, or doping Cu with another element, like Ni, is not possible. It is found that the pure and mixed Cu:Zn electrodes behave similarly in term of electrocatalytic selectivity to multi‐carbon products. At higher Zn concentrations the electrode behaves like the pure Zn catalyst, which indicates that the Cu cationic species do not have a significant influence on the selectivity to multi‐carbon products. It is found that in the non‐monotonically distribution of products is dominated in term of surface energy in which copper prefers the surface. Otherwise, this work highlights the importance of in situ characterization to uncover the mechanisms mediating the catalytic reactions in contrast to ex situ or post mortem analysis, which can be a source of misinterpretation. [ABSTRACT FROM AUTHOR]

As state-of-the-art electrochemical energy conversion and storage (EECS) techniques, fuel cells and rechargeable batteries have achieved great success in the past decades. However, modern societies' ever-growing demand in energy calls for EECS devices with high efficiency and enhanced performance, which mainly rely on the rational design of catalysts, electrode materials, and electrode/electrolyte interfaces in EESC, based on in-deep and comprehensive mechanistic understanding of the relevant electrochemical redox reactions. Such an understanding can be realized by monitoring the dynamic redox reaction processes under realistic operation conditions using in situ techniques, such as in situ Raman, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) spectroscopy. These techniques can provide characteristic spectroscopic information of molecules and/or crystals, which are sensitive to structure/phase changes resulted from different electrochemical working conditions, hence allowing for intermediates identification and mechanisms understanding. This review described and summarized recent progress in the in situ studies of fuel cells and rechargeable batteries via Raman, FTIR, and XRD spectroscopy. The applications of these in situ techniques on typical electrocatalytic electrooxidation reaction and oxygen reduction reaction (ORR) in fuel cells, on representative high capacity and/or resource abundance cathodes and anodes, and on the solid electrolyte interface (SEI) in rechargeable batteries are discussed. We discuss how these techniques promote the development of novel EECS systems and highlight their critical importance in future EECS research. [ABSTRACT FROM AUTHOR]

A low‐cost microfluidic platform integrated with a flexible heater was developed for in situ temperature‐dependent spectroscopic measurement at the point of care. After verifying the system by comparing on‐chip spectroscopic measurement of methylene blue with the conventional spectroscopy, we demonstrated its applications in temperature‐dependent absorption spectroscopy of a model biomolecule, curcumin. The system is portable, battery‐powered and requires ultra‐low volumes of analytes, which is highly suitable for point‐of‐care characterization. [ABSTRACT FROM AUTHOR]

Reductive pretreatment is an important step for activating supported metal catalysts but has received little attention. In this study, reconstruction of the supported nickel catalyst was found to be sensitive to pretreatment conditions. In contrast to the traditional activation procedure in hydrogen, activating the catalyst in syngas created supported Ni nanoparticles with a polycrystalline structure containing an abundance of grain boundaries. The unique post-activation catalyst structure offered enhanced CO adsorption and an improved CO methanation rate. The current strategy to tune the catalyst structure via manipulating the activation conditions can potentially guide the rational design of other supported metal catalysts.

Cobalt‐iron oxyhydroxides (CoFeOOHx) are among the most active catalysts for the oxygen evolution reaction (OER). However, their redox behavior and the electronic and chemical structure of their active sites are still ambiguous. To shed more light on this, the complete and rapid reconstruction of four helical cobalt‐iron borophosphates with different Co:Fe ratios into disordered cobalt‐iron oxyhydroxides can be achieved, which are electrolyte‐penetrable and thus most transition metal sites can potentially participate in the OER. To track the redox behavior and to identify the active structure, quasi in situ X‐ray absorption spectroscopy is applied. Iron in high oxidation states ≥ IV (Fe4+) and its substantial redox behavior with an average oxidation state of around 2.8 to above 3.2 is detected. Furthermore, a 6% contraction of the Fe‐O bond length compared to Fe3+OOH references is observed during OER and a strong distortion of the [MO6] octahedra is identified. It is hypothesized that this bond contraction is caused by the presence of oxyl radicals and that di‐µ‐oxyl radical bridged cobalt‐iron centers are the active sites. It is anticipated that the detailed electronic and structural description can substantially contribute to the debate on the nature of the active site in bimetallic iron‐containing OER catalysts. [ABSTRACT FROM AUTHOR]

A significant advantage of organic semiconductors over many of their inorganic counterparts is solution processability. However, solution processing commonly yields heterogeneous films with properties that are highly sensitive to the conditions and parameters of casting and processing. Measuring the key properties of these materials in situ, during film production, can provide new insight into the mechanism of these processing steps and how they lead to the emergence of the final organic film properties. The excited-state dynamics is often of import in photovoltaic, electronic, and light-emitting devices. This review focuses on single-shot transient absorption, which measures a transient spectrum in a single shot, enabling the rapid measurement of unstable chemical systems such as organic films during their casting and processing. We review the principles of instrument design and provide examples of the utility of this spectroscopy for measuring organic films during their production. [ABSTRACT FROM AUTHOR]

Abstract A low‐cost microfluidic platform integrated with a flexible heater was developed for in situ temperature‐dependent spectroscopic measurement at the point of care. After verifying the system by comparing on‐chip spectroscopic measurement of methylene blue with the conventional spectroscopy, we demonstrated its applications in temperature‐dependent absorption spectroscopy of a model biomolecule, curcumin. The system is portable, battery‐powered and requires ultra‐low volumes of analytes, which is highly suitable for point‐of‐care characterization.

Acoustic levitation is a distinctive and versatile tool for levitating and processing free-standing single droplets and particles. Liquid droplets suspended in an acoustic standing wave provide container-free environments for understanding chemical reactions by avoiding boundary effects and solid surfaces. We attempted to use this strategy for the production of well-dispersed uniform catalytic nanomaterials in an ultraclean confined area without the addition of external reducing agents or surfactants. In this study, we report on the synthesis of gold and silver nanoparticles (NPs) via acoustic levitation coupled with pulsed laser irradiation (PLI). In situ UV–Visible and Raman spectroscopic techniques were performed to monitor the formation and growth of gold and silver NPs. The PLI was used for the photoreduction of targeted metal ions present in the levitated droplets to generate metal NPs. Additionally, the cavitation effect and bubble movement accelerate the nucleation and decrease the size of NPs. The synthesized Au NPs with ∼ 5 nm size showed excellent catalytic behavior towards the conversion of 4-nitrophenol to 4-aminophenol. This study may open a new door for synthesizing various functional nanocatalysts and for achieving new chemical reactions in suspended droplets.

Photocatalytic performance can be optimized via introduction of reactive sites. However, it is practically difficult to engineer these on specific photocatalyst surfaces, because of limited understanding of atomic‐level structure‐activity. Here we report a facile sonication‐assisted chemical reduction for specific facets regulation via oxygen deprivation on Bi‐based photocatalysts. The modified Bi2MoO6 nanosheets exhibit 61.5 and 12.4 μmol g−1 for CO and CH4 production respectively, ≈3 times greater than for pristine catalyst, together with excellent stability/reproducibility of ≈20 h. By combining advanced characterizations and simulation, we confirm the reaction mechanism on surface‐regulated photocatalysts, namely, induced defects on highly‐active surface accelerate charge separation/transfer and lower the energy barrier for surface CO2 adsorption/activation/reduction. Promisingly, this method appears generalizable to a wider range of materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • In situ FT-IR is performed to understand the DAAC reaction on Ru@MIL-101(Cr). • α and β peaks are used as probes of metal-MOF interface sites and metallic sites. • n-Butanol favors the interface sites while butanal prefers the Ru metallic sites. • In situ FT-IR studies complete dynamic spectra for more analysis of kinetics. • Provide an insight of extraordinary DAAC reaction performance on the catalyst. Comparing to homogeneous systems, direct alcohol to acetals conversion (DAAC) reaction through heterogeneous catalysts has obvious advantages of simple separation, less corrosion and waste. However, progress on this research is quite limited. Recently a breakthrough of Ru@MIL-101(Cr) catalyst was found with high selectivity and conversion for DAAC of aliphatic alcohol and diols towards desired products. In this study, time resolved in situ FT-IR was performed for capturing molecular-level information on the active sites of the catalysis system. Transients analysis of interaction between n-butanol/butanal and two active surface sites induced by Ru loading on MIL-101(Cr) provides key insight into the reaction, revealing that Ru@ MIL-101(Cr) confines the reaction to the ideal acidic sites between Ru nanoparticles and MIL-101(Cr) support for efficient process. [ABSTRACT FROM AUTHOR]

Here we introduce PRISMA, an open‐source tool to rapidly analyse large numbers of spectra into meaningful spectroscopic trends. PRISMA follows a human‐in‐the‐loop workflow, where the user interacts with an intuitive graphical user interface to control multiple steps in the spectrum analysis process: trimming, baseline correction, and peak fitting. The tool outputs the results in an easy‐to‐read csv format within seconds. We describe the functionalities implemented in PRISMA and test its capabilities with three experimental cases relevant to the study of Electrochemical energy storage and conversion devices: a temperature‐dependent Raman measurement of phase transitions, a linear Raman mapping of a graphite composite electrode, and an operando X‐ray diffraction experiment of lithium nickel oxide composite battery electrode. The case studies demonstrate the robustness of the app and its ability to unearth insightful trends in peak parameters, which are easier to represent, interpret and further analyse with more advanced techniques. [ABSTRACT FROM AUTHOR]

Abstract Electrochemical conversion of abundant resources, such as carbon dioxide, water, nitrogen, and nitrate, is a remarkable strategy for replacing fossil fuel-based processes and achieving a sustainable energy future. Designing an efficient and selective electrocatalysis system for electrochemical conversion reactions remains a challenge due to a lack of understanding of the reaction mechanism. Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) is a promising strategy for experimentally unraveling a reaction pathway and rate-limiting step by detecting intermediate species and catalytically active sites that occur during the reaction regardless of substrate. In this review, we introduce the SHINERS principle and its historical developments. Furthermore, we discuss recent SHINERS applications and developments for investigating intermediate species involved in a variety of electrocatalytic reactions.

[Display omitted] • Olefin metathesis is a commercially successful method for converting less valuable olefins into more valuable ones; • Modification of the γ-Al 2 O 3 acidic properties by treatment with NH 4 HF 2 , (NH 4) 2 SiF 6 , H 3 BO 3 leads to a significant increase in the catalytic activity of MoO 3 /Al 2 O 3 systems in propylene metathesis; • An increase in conversion in the propylene metathesis reaction correlates with an increase in the concentration of strong Brønsted acid sites on the surface of the catalysts; • The formation of centers active in propylene metathesis occurs when the substrate interacts with strong Brønsted, but not Lewis acid sites on the surface of the catalyst; • Highly selective promoted olefin metathesis catalyst provides propylene conversion 8.5 times higher compared to classical, unmodified MoO 3 /Al 2 O 3 systems. One important way to increase the production of higher-margin products from less valuable unsaturated hydrocarbons is the widely used process of catalytic metathesis. Progress in the development of more advanced metathesis catalysts is hampered by obvious gaps in scientific knowledge about this process. This work is aimed at establishing the influence of physicochemical properties of Mo-containing lower olefins metathesis catalysts and developing methods for increasing their activity through promotion. A classic support for Mo-oxide metathesis catalyst was promoted with NH 4 HF 2 , (NH 4) 2 SiF 6 , H 3 BO 3 additives. The synthesized systems were analyzed by a large set of methods. The catalytic properties of obtained systems were determined in the propylene metathesis reaction. It was shown that the proposed promotion leads to an increase in activity of the catalyst up to 8.5 times. It was shown that strong Brønsted acid sites play a decisive role in increasing activity. In addition, it has been experimentally proven that the formation of active centers occurs when the substrate interacts with Brønsted, but not Lewis acid sites on the surface of the catalyst. The discoveries obtained in this work can serve as the basis for the creation of a new generation highly active lower olefins metathesis catalysts. [ABSTRACT FROM AUTHOR]

The photocatalytic efficiency for removing volatile organic compounds (VOCs) is significantly influenced by operational parameters like humidity and flow velocity, exhibiting notable and inconsistent fluctuations in both lab-scale and large-scale demonstrations. In this study, operando spectroscopy and isotope analysis were employed to investigate the correlation between humidity levels and degradation of gaseous acetaldehyde using TiO 2 photocatalysts, aiming to demonstrate the scaling-up of photocatalytic air purifier. It was observed that rate constants for the mineralization of acetaldehyde rapidly decreased by 30% as relative humidity increased from 25% to 80% in the flow system (with an air velocity, v = 0.78 m/s). However, batch system showed smaller change with only a 10% reduction of the rate constant. Humidity fluctuations were more pronounced under high-speed conditions and were amplified in air purifier (v = 3.8 m/s). Time-resolved operando spectroscopy using an 13C isotope of acetaldehyde revealed that humidity's distinct role in dark adsorption and photocatalytic reactions. Water was found to inhibit the formation of crotonaldehyde during aldol condensation reaction in dark condition. Moreover, water suppressed photocatalytic mineralization by inhibiting acetate oxidation to formate. These findings provide valuable insights for improving realistic air purification processes, underscoring the importance of identifying key intermediates and controlling humidity to enhance the selectivity of gaseous pollutant oxidation reactions. [Display omitted] • The impact of humidity amplifies in TiO 2 photocatalysis under high air velocity. • The influence of humidity intensifies in TiO 2 photocatalysis during large-scale demonstrations. • The rate of acetaldehyde decomposition rapidly increases with decreasing humidity. • H 2 O molecules hinder the aldol condensation reaction on the TiO 2 surface. • H 2 O molecules impede formate formation on the TiO 2 during acetate oxidation. [ABSTRACT FROM AUTHOR]

Abstract The electrochemical CO2 reduction reaction (CO2RR) has been regarded as a promising technique for converting CO2 into high‐value fuels and chemicals. Powered by renewable electricity, the CO2RR provides a viable strategy to mitigate the CO2 concentration in the atmosphere and close the anthropogenic carbon cycle. Recent studies exhibit that copper‐based catalysts are capable of reducing CO2 to C2+ products, such as ethylene and ethanol, which are of higher value compared with C1 products. The reaction process toward C2+ products involves the formation of key intermediate *CO, the C–C bonding, and the post‐C–C bonding to final products. This perspective is focusing on the mechanism leading to C2+ products, examining the evidence from in situ/operando spectroscopy and density functional theory calculations. The effects of Cu facet and electrolyte on catalytic performance are reviewed. An in depth discussion of mechanistic aspects of Cu catalyst is presented, shedding light on the intrinsic features of catalyst and electrode‐electrolyte interface, therefore moving towards an understanding of CO2RR at the atomic level.

Lithium‐ion batteries are commonly used for electrical energy storage in portable devices and are promising systems for large‐scale energy storage. However, their application is still limited due to electrode degradation and stability issues. To enhance the fundamental understanding of electrode degradation, we report on the Raman spectroscopic characterization of LiCoO2 cathode materials of working Li‐ion batteries. To facilitate the spectroscopic analysis of the solid electrolyte interface (SEI), we apply in situ surface‐enhanced Raman spectroscopy under battery working conditions by using Au nanoparticles coated with a thin SiO2 layer (Au@SiO2). We observe a surface‐enhanced Raman signal of Li2CO3 at 1090 cm−1 during electrochemical cycling as an intermediate. Its formation/decomposition highlights the role of Li2CO3 as a component of the SEI on LiCoO2 composite cathodes. Our results demonstrate the potential of Raman spectroscopy to monitor electrode/electrolyte interfaces of lithium‐ion batteries under working conditions thus allowing relations between electrochemical performance and structural changes to be established. [ABSTRACT FROM AUTHOR]

The development of novel earth‐abundant metal‐based catalysts to accelerate the sluggish oxygen evolution reaction (OER) is crucial for the process of large‐scale production of green hydrogen. To solve this bottleneck, herein, a simple one‐pot colloidal approach is reported to yield crystalline intermetallic nickel silicide (Ni2Si), which results in a promising precatalyst for anodic OER. Subsequently, an anodic‐coupled electrosynthesis for the selective oxidation of organic amines (as sacrificial proton donating agents) to value‐added organocyanides is established to boost the cathodic reaction. A partial transformation of the Ni2Si intermetallic precatalyst generates a porous nickel(oxy)hydroxide phase modified with oxidic silicon species as unequivocally demonstrated by a combination of quasi in situ Raman and X‐ray absorption spectroscopy as well as ex situ methods. The activated form of the catalyst generates a geometric current density of 100 mA cm−2 at an overpotential (η100) of 348 mV displaying long‐term durability over a week and high efficiency in paired electrolysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Turnover rates for epoxidation on dispersed Ti atoms vary by 1000-fold with identity of oxide support. • Apparent activation enthalpies (ΔH‡ epox) span 85 kJ mol−1 across Ti-based catalysts. • In situ spectroscopy does not detect differences among electronic structures of reactive intermediates (Ti-OOH/O 2). • Isoelectric points and water uptakes on oxides correlate with ΔH‡ epox. • Acidic supports concentrate water near the solid-liquid interfaces and lower ΔH‡ epox values. Atomically disperse Ti sites on metal oxides (MO x , including SiO 2 , γ-Al 2 O 3 , ZnO, GeO 2) activate H 2 O 2 to create intermediates active for alkene epoxidations. Turnover rates for 1-hexene epoxidation in acetonitrile vary 1000-fold at identical conditions due to differences in apparent activation enthalpies (ΔH‡ epox) and entropies (ΔS‡ epox). Ligand-to-metal charge transfer energies and vibrational frequencies of reactive species assessed by in situ UV–Vis and Raman spectroscopy, respectively, indicate supports do not detectably change electronic properties of H 2 O 2 -derived intermediates. However, isoelectric points and solution-phase water uptakes for these metal oxides correlate with ΔH‡ epox and suggest that non-covalent interactions at the solid-liquid interface influence the stability of epoxidation transition states. Supports with lower pK a values concentrate water near the solid-liquid interface and enthalpically stabilize the transition state. These findings illustrate that outer sphere interactions impact epoxidation reactions upon metal oxide catalysts including titanium silicates. [ABSTRACT FROM AUTHOR]

Acidic CO2 electrolysis offers a promising strategy to achieve high carbon utilization and high energy efficiency. However, challenges remain in suppressing the competitive hydrogen evolution reaction (HER) and improving product selectivity. High concentrations of potassium ions (K+) can suppress HER and accelerate CO2 reduction, but they still inevitably suffer from salt precipitation problems. In this study, we demonstrate that the sulfonate-based polyelectrolyte, polystyrene sulfonate (PSS), enables to reconstruct the electrode-electrolyte interface to significantly enhance the acidic CO2 electrolysis. Mechanistic studies reveal that PSS induces high local K+ concentrations through electrostatic interaction between PSS anions and K+. In situ spectroscopy reveals that PSS reshapes the interfacial hydrogen-bond (H-bond) network, which is attributed to the H-bonds between PSS anions and hydrated proton as well as the steric hindrance of the additive molecules. This greatly weakens proton transfer kinetics and leads to the suppression of undesirable HER. As a result, a Faradaic efficiency of 93.9% for CO can be achieved at 250 mA cm-2, simultaneous with a high single-pass carbon efficiency of 72.2% on commercial Ag catalysts in acid. This study highlights the important role of the electrode-electrolyte interface induced by polyelectrolyte additives in promoting electrocatalytic reactions., (© 2024 Wiley‐VCH GmbH.)

M-N-C-type single-atom catalysts (SACs) are highly efficient for the electrocatalytic oxygen evolution reaction (OER). And the isolated metal atoms are usually considered real active sites. However, the oxidative structural evolution of coordinated N during the OER will probably damage the structure of M-N-C, hence resulting in a completely different reaction mechanism. Here, we reveal the aggregation of M-N-C materials during the alkaline OER. Taking Ni-N-C as an example, multiple characterizations show that the coordinated N on the surface of Ni-N-C is almost completely dissolved in the form of NO3-, accompanied by the generation of abundant O functional groups on the surface of the carbon support. Accordingly, the Ni-N bonds are broken. Through a dissolution-redeposition mechanism and further oxidation, the isolated Ni atoms are finally converted to NiOOH nanoclusters supported by carbon as the real active sites for the enhanced OER. Fe-N-C and Co-N-C also have similar aggregation mechanism. Our findings provide unique insight into the structural evolution and activity origin of M-N-C-based catalysts under electrooxidative conditions., (© 2024 Wiley‐VCH GmbH.)

Conventional strategies for highly selective and active hydrogen peroxide (H 2 O 2 ) electrosynthesis primarily focus on catalyst design. Electrocatalytic reactions take place at the electrified electrode-electrolyte interface. Well-designed electrolytes, when combined with commercial catalysts, can be directly applied to high-efficiency H 2 O 2 electrosynthesis. However, the role of electrolyte components is equally crucial but is significantly under-researched. In this study, anionic surfactant n-tetradecylphosphonic acid (TDPA) and its analogs are used as electrolyte additives to enhance the selectivity of the two-electron oxygen reduction reaction. Mechanistic studies reveal that TDPA assembled over the electrode-electrolyte interface modulates the electrical double-layer structure, which repels interfacial water and weakens the hydrogen-bond network for proton transfer. Additionally, the hydrophilic phosphonate moiety affects the coordination of water molecules in the solvation shell, thereby directly influencing the proton-coupled kinetics at the interface. The TDPA-containing catalytic system achieves a Faradaic efficiency of H 2 O 2 production close to 100% at a current density of 200 mA cm -2 using commercial carbon black catalysts. This research provides a simple strategy to enhance H 2 O 2 electrosynthesis by adjusting the interfacial microenvironment through electrolyte design., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

The intensive study of electrochemical CO 2 reduction reaction (CO 2 RR) has resulted in numerous highly selective catalysts, however, most of these still exhibit uncontrollable selectivity. Here, it is reported for the first time the controllable CH 4 /C 2 H 4 selectivity by modulating the electronic states of Cu incorporated in metal-organic frameworks with different functional ligands, achieving a Faradaic efficiency of 58% for CH 4 on Cu-incorporated UiO-66-H (Ce) composite catalysts, Cu/UiO-66-H (Ce) and that of 44% for C 2 H 4 on Cu/UiO-66-F (Ce). In situ measurements of Raman and X-ray absorption spectra revealed that the electron-withdrawing ability of the ligand side group controls the product selectivity on MOFs through the modulation of the electronic states of Cu. This work opens new prospects for the development of MOFs as a platform for the tailored tuning of selectivity in CO 2 RR., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Structural reconstruction is a process commonly observed for Cu‐based catalysts in electrochemical CO2 reduction. The Cu‐based precatalysts with structural complexity often undergo sophisticated structural reconstruction processes, which may offer opportunities for enhancing the electrosynthesis of multicarbon products (C2+ products) but remain largely uncertain due to various new structural features possibly arising during the processes. In this work, the Cu2O superparticles with an assembly structure are demonstrated to undergo complicated structure evolution under electrochemical reduction condition, enabling highly selective CO2‐to‐C2+ products conversion in electrocatalysis. As revealed by electron microscopic characterization together with in situ X‐ray absorption spectroscopy and Raman spectroscopy, the building blocks inside the superparticle fuse to generate numerous grain boundaries while those in the outer shell detach to form nanogap structures that can efficiently confine OH− to induce high local pH. Such a combination of unique structural features with local reaction environment offers two important factors for facilitating C−C coupling. Consequently, the Cu2O superparticle‐derived catalyst achieves high faradaic efficiencies of 53.2% for C2H4 and 74.2% for C2+ products, surpassing the performance of geometrically simpler Cu2O cube‐derived catalyst and most reported Cu electrocatalysts under comparable conditions. This work provides insights for rationally designing highly selective CO2 reduction electrocatalysts by controlling structural reconstruction. [ABSTRACT FROM AUTHOR]

In this work we elucidate the main steps of the CO oxidation mechanism over Au/CeO2(111), clarifying the course of CO adsorption at a broad variety of surface sites as well as of transmutations of one CO species into another. By combining transient spectroscopy with DFT calculations we provide new evidence that the active centers for CO conversion are single gold atoms. To gain insight into the reaction mechanism, we employ Modulation Excitation (ME) DRIFT spectroscopy in combination with the mathematical tool of Phase Sensitive Detection to identify the active species and perform DFT calculations to facilitate the assignments of the observed bands. The transient nature of the ME-DRIFTS method allows us to sort the observed species temporally, providing further mechanistic insight. Our study highlights the potential of combined transient spectroscopy and theoretical calculations (DFT) to clarify the role of adsorbates observed and to elucidate the reaction mechanism of CO oxidation over supported gold and other noble-metal catalysts. [ABSTRACT FROM AUTHOR]

To advance the widespread implementation of electrochemical energy storage and conversion technologies, the development of inexpensive electrocatalysts is imperative. In this context, Fe/N/C‐materials represent a promising alternative to the costly noble metals currently used to catalyze the oxygen reduction reaction (ORR), and also display encouraging activities for the reduction of CO2. Nevertheless, the application of these materials in commercial devices requires further improvements in their performance and stability that are currently hindered by a lack of understanding of the nature of their active sites and the associated catalytic mechanisms. With this motivation, herein the authors exploit the high sensitivity of modulation excitation X‐ray absorption spectroscopy toward species undergoing potential‐induced changes to elucidate the operando local geometry of the active sites in two sorts of Fe/N/C‐catalysts. While the ligand environment of a part of both materials' sites appears to change from six‐/five‐ to fourfold coordination upon potential decrease, they differ substantially when it comes to the geometry of the coordination sphere, with the more ORR‐active material undergoing more pronounced restructuring. Furthermore, these time‐resolved spectroscopic measurements yield unprecedented insights into the kinetics of Fe‐based molecular sites' structural reorganization, identifying the oxidation of iron as a rate‐limiting process for the less ORR‐active catalyst. [ABSTRACT FROM AUTHOR]