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Abstract: Potassium-ion batteries (KIBs) are a promising beyond–lithium-ion chemistry, offering advantages similar to sodium-ion systems in terms of earth-abundant materials and safety, with the additional benefit of reversible graphite intercalation and potential for improved low-temperature performance. These features make KIBs attractive for low-cost electric vehicles and stationary battery energy storage systems. However, they currently fall short of the cycle life required by these applications. A major source of capacity fade is instability of the solid electrolyte interphase (SEI), which is influenced by electrolyte chemistry, temperature, and the electrochemical history of the cell. Many studies use potassium metal as a proxy to investigate SEI behaviour on graphite. On potassium metal, the SEI can form chemically via direct reaction with the electrolyte or electrochemically during potassium plating. In contrast, during charging of a graphite electrode, SEI formation occurs exclusively through electrochemical reduction. It therefore remains unclear to what extent the SEI formed on potassium metal is representative of that formed on graphite. Here, we employ X-ray photoelectron spectroscopy (XPS) to probe differences between chemical and electrochemical SEI formation on potassium metal, graphite, and inert electrodes in two contrasting potassium bis(fluorosulfonyl)imide (KFSI)-based electrolytes: 1 m KFSI in tetraethylene glycol dimethyl ether (G4) and 1 m KFSI in 1,3-dioxane (13-DX). Four-dimensional scanning transmission electron microscopy (4D-STEM) phase mapping provides complementary structural insight. We establish relationships between SEI chemistry, electrolyte composition, electrode material, formation pathway, and applied potential, offering guidance for rational electrolyte design.

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Abstract: Halide perovskite light-emitting diodes promise high-efficiency1,2,3, low-cost optoelectronics, yet their operational instability remains a critical barrier to practical deployment. Here we develop a multimodal in situ electron microscopy approach that integrates four-dimensional scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy and atomic-resolution imaging to directly visualize structural and chemical evolution in a working halide perovskite light-emitting diode with nanometre precision. Our in situ biasing measurements uncover nanoscale structural and chemical transformations initiated at transport layer interfaces, including the formation of metallic lead and lead-rich secondary phases, as well as strain-driven grain fragmentation. On biasing, we observe the partial transformation of the metallic Al contact to insulating AlCl3. Crucially, whereas the bulk of the perovskite emitter remains relatively intact, our experiment shows that degradation is localized at interfaces. By comparing in situ and ex situ measurements, these results establish a mechanistic link between interfacial strain, ionic transport and electrochemical reactions in working devices, and provide a broadly applicable framework for nanoscale degradation analysis in complex multilayered optoelectronic systems using multimodal in situ biasing microscopy.

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Abstract: Carbon monoxide is one of the most hazardous pollutants in automotive gas exhaust emissions due to its severe impact on the human body and environment. There are many methods for CO removal, including adsorption, methanation, and catalytic oxidation. Catalyst oxidation has been considered the most efficient technique for CO removal. Although CO oxidation has received extensive attention in past decades, achieving high activity and stability at both engine working and cold starting temperatures is still challenging. Noble metal catalysts generally exhibit excellent catalytic activity in high-temperature regions. However, it still suffers from several obstacles, such as over-absorption of CO in low-temperature regions for Pt-based catalysts. Therefore, researchers still focus on seeking alternative candidates for noble metals due to their high cost and low availability, promising non-noble metals including manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu) receive increasing attention due to their high catalytic activity and stability. Many forms of catalysts have been studied exclusively, such as metal catalysts, metal oxide catalysts, supported catalysts, zeolite, and carbon-based catalysts. Supported catalysts with available metal surface area and unique metal-support interfacial perimeter play pivotal roles in heterogeneous catalysis across various industrial applications. Depending on the size of supported active metal, supported metal catalysts can be categorized into particle, cluster, and single-atom catalysts. Among these, single-atom catalysts (SACs) with relatively specific active structures offer prominent advantages in optimizing catalytic activity and product selectivity, leading to an increasing interest in this research area. In recent years, the catalytic performance of SACs has been largely improved through some reported methods including adjusting coordination number, doping heterogeneous atoms, modulating support anchoring sites, and so on. Despite these advancements, it has always been ignored that with the change of the catalyst synthetic process as well as the metal-support interaction (MSI), supported active sites may appear at different positions in catalyst supports, especially at surface or subsurface, thus exhibiting distinct different catalytic behaviour with surrounding molecules. However, the isolated metal site-related location effect is very difficult to deeply explore, because the complexity of catalyst synthesis, combined with the absence of a metal atom location descriptor, poses significant obstacles to achieving precise control over the location of active metal. Herein, we first proposed an electronic metal-support-carbon interaction (EMSCI), which provides a complete picture of the mass and electron flow and expands on the traditional electronic metal-support interactions (EMSI) concept. Furthermore, we reported an exception of EMSI where the interaction between support and metal is not necessary to achieve a high catalytic activity in the CO oxidation reaction, especially in low-temperature regions. The reducibility of CeO2 is investigated by Ce L3 and M4,5 edge NEXAFS, it is confirmed that CeO2 cannot be reduced even under the reductive conditions. Moreover, the location-dependent Cu species have been investigated which are formed during the hydrothermal process using both ex situ and in situ X-ray techniques. The CO oxidation activity shows a positive relation to the percentage of Cu(CO)+ species detected during the reaction. Such behaviour resembles the intrinsic catalytic activity of a true Cu(CO)+ single site, in which the support is completely inactive. This unique phenomenon provides a new scope of understanding metal support interaction and a pathway to optimizing single-atom catalyst performance and catalyst design.

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Abstract: The Noise2Void technique is demonstrated for successful denoising of atomic resolution scanning transmission electron microscopy (STEM) images. The technique is applied to denoising atomic resolution images and videos of gold adatoms on a graphene surface within a graphene liquid-cell, with the denoised experimental data qualitatively demonstrating improved visibility of both the Au adatoms and the graphene lattice. The denoising performance is quantified by comparison to similar simulated data and the approach is found to significantly outperform both total variation and simple Gaussian blurring. Compared to other denoising methods, the Noise2Void technique has the combined advantages that it requires no manual intervention during training or denoising, no prior knowledge of the sample and is compatible with real-time data acquisition rates of at least 45 frames per second.

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Abstract: A series of PdZn/TiO2 catalysts prepared by chemical vapor impregnation (CVI) were tested for CO2 hydrogenation at 20 bar pressure and at temperatures of 230–270 °C. Changing the Pd and Zn molar ratio (Zn:Pd = 0–20) in a PdZn/TiO2 catalyst has a dramatic effect on selectivity for the CO2 hydrogenation reaction. Pd alone shows three main products: methanol, CO, and methane. Addition of small quantities of Zn results in the formation of a PdZn alloy, preventing methanation. At equimolar ratios of Pd and Zn, a 1:1 β-PdZn alloy is formed and a reverse water gas shift catalyst is produced. Adding Zn in excess relative to the Pd loading results in the formation of ZnO on the TiO2 surface in addition to the PdZn alloy, dramatically increasing methanol selectivity from 5% at Zn:Pd = 1 to 55% for Zn:Pd = 2. Through a combination of theory and experiment, the active site for methanol synthesis is concluded to be the interface between PdZn nanoparticles and the ZnO overlayer on the TiO2, where interfacial formate can react with hydrogen dissociated by the metal nanoparticle.