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Abstract: X-ray photoelectron spectroscopy (XPS) is a major technique in catalyst research due to its ability to determine chemical states on the surface. Near ambient pressure XPS (NAP-XPS) enables in situ analysis, offering valuable insight into catalytic processes. However, modern catalysts are often supported on non-conductive supports such as TiO2 or SiO2, which can present significant challenges for XPS analysis due to charging and differential charging. These issues can distort spectral data, rendering data unusable and wasting valuable instrument time. While several sample preparation strategies exist, many are limited by not allowing high temperature analysis, the risk of sample loss (e.g., from powder flaking off), or continued susceptibility to charging. In this work, we introduce a simple, robust, and time-efficient method for mounting catalyst powders by compressing them between aluminium foil disks. This approach provides excellent sample hold, minimises charging effects, and is suitable for high-temperature NAP-XPS analysis and synchrotron x-ray sources. The method addresses key limitations of conventional preparation techniques and enables more reliable characterisation of insulating catalyst materials.

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Abstract: Geopolymer cements are highly promising materials for long-term immobilisation of Strontium-90 radioactive waste, offering superior durability and cation binding sites compared to conventional Portland cement matrices. This study investigates the influence of prolonged leaching on the Sr immobilisation mechanism and structural integrity of metakaolin-based geopolymers using the ANSI/ANS 16.1 semi-dynamic leaching test. All geopolymers demonstrated high Sr retention, with Leachability Indices at least 14.7 for all samples, significantly exceeding the industry guideline of 6.0, confirming their effectiveness. Importantly, potassium silicate–activated geopolymers exhibited reduced Sr release and substantially lower leaching rates than sodium silicate–activated geopolymers. Multiscale spectroscopic and diffractometric analysis, including synchrotron X-ray absorption spectroscopy and multinuclear high-field solid-state MAS NMR probing 39K, 23Na, 27Al, and 29Si, revealed that the alkali aluminosilicate gel framework remained structurally stable after leaching for 28 days, with no significant alterations to Si and Al bonding environments. Sr release is primarily controlled by diffusion, and the dominant immobilisation mechanism is the formation of insoluble SrCO3. Atomic-level Sr structural analysis using XANES/EXAFS revealed an increase in the average Sr coordination number in both systems after leaching, with a more pronounced rise in potassium-based geopolymers, consistent with enhanced SrCO3 formation. Overall, these findings demonstrate that geopolymers maintain structural integrity during leaching and show for the first time that using potassium rather than sodium as an alkali activator is definitively more advantageous for maximising the long-term effectiveness of geopolymer wasteforms. This demonstrates their strong suitability as wasteforms for the safe long-term immobilisation of Sr-containing radioactive wastes.

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Abstract: Industrial W-based olefin metathesis catalysts use silica as the support and generally show low activities. This is due to the difficulty in dispersing W species and in maintaining the structural integrity of W active centers on the silica surface. These catalysts also have poor W redox kinetics and slow olefin adsorption at reaction temperatures, which prohibits high reaction rates. Here, for the first time, we systematically demonstrate the dramatic multiple contributions from zeolite Y to the overall catalytic activity when it is used as the catalyst support. The high surface area and porous nature of zeolite Y can provide the isolation, immobilization, and confinement of W active centers. Isolated W active centers in zeolite Y show faster redox kinetics, which is crucial for olefin metathesis. Zeolite Y also facilitates rapid adsorption and isomerization of olefin substrates by its Brønsted acid sites for synergetic catalysis with W active centers.

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Abstract: Formamidinium lead iodide (FAPbI3), which has a narrower band gap close to the Shockley-Queisser limit, offers higher power conversion efficiency (PCE) than other perovskite compositions, surpassing 27% [1]–[3]. However, under external stressors like moisture in ambient air processing conditions, its high tolerance factor value causes phase instability because of the larger ion size of FA+ [4]–[6]. Additionally, a higher annealing temperature (>390 K) is needed to reach the cubic α-phase of FAPbI3, whereas lower temperatures result in the formation of a non-photoactive δ-phase [7]. In recent years, FAPbI3 perovskite ink has been extensively incorporated with volatile methylammonium chloride (MACl) as a transitional stabilizer [8]. This substance effectively provides FAPbI3 black phase without annealing by decreasing the formation energy. However, the advantageous effects of MACl as an α-phase FAPbI3 inducer and stabilizer at room temperature are neutralized under ambient conditions and in the presence of non-volatile coordinating DMSO, which is frequently used as a co-solvent with toxic DMF to regulate the crystallization process [9]. DMSO accelerates the α-to-δ phase transition in air by displacing MACl from the intermediate film through the formation of stronger bonds with PbI2. In this work, we use recently emerged Triethyl Phosphate (TEP) as a green solvent to dissolve FAPbI3 precursors and in-situ study its crystallization kinetics in the presence of MACl and excess PbI2 under ambient condition using transmission wide angle x-ray scattering (T-WAXS) [10] and steady-state photoluminescence (PL) techniques. Our results show that, unlike DMSO containing solvent systems, TEP with appropriate coordination ability allows for direct solvent extraction during anti-solvent quenching process avoiding intermediate phase formation. Furthermore, it has been found that the addition of excess PbI2 to the perovskite solution, along with MACl, not only regulates the pre-nucleation stage, leading to larger and more ordered crystals, as opposed to MACl alone as an additive, but also accelerates the formation of α-phase FAPbI3 at room temperature and stabilizes it under ambient condition during spin casting. This study paves the way for achieving high efficiency FAPbI3 solar cells using a non-toxic solvent system and under ambient conditions.

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Abstract: Analytical expressions for the damage-limited resolution (DLR) are developed and applied to X-ray and electron imaging of beam-sensitive specimens, allowing for variation of the characteristic radiation dose with spatial resolution. The dependence of DLR on specimen thickness is illustrated for the common modes of X-ray and transmission electron-microscope imaging. Similarities and differences between the radiolysis damage caused by electrons and X-rays are discussed. The meaning of a `Bragg boost' in diffracted intensity is discussed.