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Abstract: X-ray Photoelectron Spectroscopy (XPS) is a powerful tool for probing the chemical and electronic states of materials with elemental specificity and surface sensitivity. However, its application in the tender X-ray range (1–5 keV) for synchrotron radiation has remained limited due to the limited choice of optics capable of maintaining high reflectivity and efficiency in this energy window. To address this, multilayer (ML) grating structures have become increasingly popular, offering significantly higher efficiency than SL coatings in the tender X-ray region. This paper presents the development of ML laminar gratings optimised for enhancing efficiency in the tender X-ray range, and capable of retaining performance under intense X-ray exposure in the oxygen partial pressure of 10 mbar. The ML coating quality was verified through X-ray reflectivity (XRR), XPS and near-edge X-ray absorption fine structures (NEXAFS) measurements, while the performance of the grating was validated through beamline flux transmission and XPS measurements. The MLLG demonstrated 22 higher intensity in flux and XPS, significantly improving the signal-to-noise ratio. Most importantly, the MLLGs outperformed traditional designs by offering improved spectral resolution while maintaining measurement capability at varying values without compromising the intensity. Furthermore, we demonstrated that the incorporation of nitrogen during deposition further enhances flux transmission.

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Abstract: Tuning the electronic properties of nanocatalysts via doping with monodispersed hetero-metal atoms is an effective method used to enhance catalytic properties. Doping CuO nanoparticles with monodispersed Co atoms using different reductants affords catalysts (CoBCu/Al2O3 and CoHCu/Al2O3) with strikingly different electronic structures. Compared to CoHCu/Al2O3, the CuO nanoparticles in CoBCu/Al2O3 have longer and weaker Cu-O bonds, with a lower 1s → 4pz antibonding transition and higher 4p → 1s bonding transition (as demonstrated from HERFD-XANES and valence-to-core X-ray emission spectroscopy). The weaker Cu-O bonds in CoBCu/Al2O3 lead to superior redox activity of the CuO nanoparticles, evidenced from operando XAFS and in-situ near ambient pressure-near edge X-ray absorption fine structures studies. Such superior redox properties of CuO in CoBCu/Al2O3 result in a much reduced activation energy of CoBCu/Al2O3 compared to CoHCu/Al2O3 (40.0 vs. 63.5 kJ/mol), thus leading to an enhancement in catalytic performance in the selective catalytic oxidation of NH3 to N2.

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Abstract: The distribution of elements within alloy nanoparticles is a critical parameter for their electrocatalytic performance. Here, we use the case of a Pt3Ni alloy to show that this elemental distribution can dynamically respond to the applied potential, leading to strongly potential-dependent catalytic properties. Starting from the Pt3Ni core and Pt shell structure that forms in acid electrolyte due to Ni leaching, our electrochemical X-ray photoelectron spectroscopy measurements show that the Ni atoms can be reversibly moved between the core of the particles and the near-surface region using the applied potential. Through potential jump measurements, we show that this Ni migration modulates the hydrogen evolution reaction activity of the particles by over 30%. These observations highlight the potential of incorporating in situ restructuring of alloys as the final step in electrocatalyst design.

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Abstract: Photocatalytic micro/nanomotors have emerged as promising tools for environmental remediation, biosensing, and targeted delivery. To enhance their light-driven propulsion, significant efforts have focused on engineering semiconductor heterostructures, which promote charge separation. However, a clear understanding of how these architectures govern photocatalytic mechanisms and influence motion performance remains limited. Here, we design a visible light-responsive nanomotor based on a Fe2O3-Pt-TiO2 trilayered heterostructure, combining narrow-bandgap α-Fe2O3 and wide-bandgap TiO2 with an intermediate Pt layer. Remarkably, Fe2O3-TiO2 nanomotors without the Pt layer exhibit only modest propulsion under visible light, whereas the inclusion of Pt significantly enhances their motility. Through advanced techniques, including in situ synchrotron radiation-based near-ambient pressure X-ray photoelectron spectroscopy and transient absorption spectroscopy, we reveal that Pt serves as an efficient electron mediator, enabling directional charge transfer across the heterojunction. This study provides fundamental insights into charge transport in multicomponent nanomotors and introduces a rational strategy for designing efficient photoactive systems.

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Abstract: The Sabatier reaction (CO2 methanation) represents a facile catalytic process to produce CH4 at relatively low temperatures and with high yields. Ni supported on ceria (Ni/CeO2) is widely recognised as an active catalyst due to the enriched Ni–CeOx interfacial sites. Here, the physicochemical properties of Ni/CeO2 are investigated by a variety of characterisation methods, including but not limited to X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and kerr-gated Raman to establish structure-activity relationships for CO2 methanation. In Chapter 3, the critical role of Ni availability, affected by both Ni particle size and potential encapsulation by reduced CeOx due to a strong metal-support interaction (SMSI), in forming interfacial sites, is highlighted. Chapter 4 examines the positive role of the surface oxygen vacancies (Ov) which was found to enhance Ni availability and MSI in Ni/CeO2 catalysts by creating a disordered and defective ceria film at the interface. This defect-dense Ni–CeOx interface altered the bonding mode between bidentate carbonates during the reaction. Results in chapter 5 evidenced the presence of Ni encapsulation, and confirmed the catalyst stability under at different activation temperatures and operating conditions. In Chapter 6, a two-dimensional (2D) Ni/CeO2 with single Ni NPs on CeO2 (100) crystal was explored using quasi in situ X-ray photoemission electron microscope (X-PEEM) and soft XAS. Detailed spatial analysis of Ni NPs and the surrounding Ce environment proposed the positive role of MSI for Ni reducibility and potential tuning methods. Also, the potential reconfigurations of Ni/CeO2 (e.g. oxidation/reduction and sintering/redispersion), were revealed under CO2 hydrogenation. In summary, the comprehensive research allowed us to better understand the role of Ov, Ni size and MSI in the formation of interfacial sites, and the correlation among these properties, essential for future designs of promising supported Ni catalysts for CO2 hydrogenation.