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Daniel J.
Zheng
,
Kaylee
Mccormack
,
Jiayu
Peng
,
Raul
Garcia-Diez
,
Elmar Yu
Kataev
,
Fabian
Schwarz
,
Susan
Nehzati
,
Jakob
Thyr
,
Wilson
Quevedo-Garzon
,
Benjamin
Howchen
,
Marcus
Bär
,
Yuriy
Román-Leshkov
,
Yang
Shao-Horn
,
Mikaela
Görlin
Abstract: The oxygen evolution reaction (OER) is crucial for electrofuel production. Metal–hydroxide organic frameworks (MHOFs), a subset of metal–organic frameworks with oxyhydroxide-like layers interconnected via organic linkers, have shown great promise as OER electrocatalysts. This study investigates lattice oxygen exchange in four Ni- and Fe-substituted MHOFs with varying linker stabilities using 18O isotope labeling combined with operando Raman spectroscopy. A negative correlation between 18O/16O lattice oxygen exchange and the OER activity is shown, with Fe ions further suppressing exchange. Operando X-ray spectroscopy (XAS) and UV–vis further reveals that lattice oxygen exchange primarily proceeds on reduced Ni2+ sites, with higher linker stability preserving more Ni2+ sites and promoting greater lattice oxygen exchange. Supported by density functional theory, the MHOF surface transforms into an OER-active MOxHy-like phase, explaining the negative correlation of lattice exchange with the OER activity. This work also identifies a noninnocent role of the Raman laser in inducing lattice oxygen exchange and offers critical insights into various lattice oxygen exchange pathways in MHOFs, demonstrating their distinction from the catalytic lattice oxygen evolution reaction mechanism.
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Dec 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[38116]
Open Access
Abstract: Increasing use of lithium-ion batteries (LIBs) urges for efficient recycling strategies for their components. Direct recycling methods for cathode materials, based on repairing the structure of the degraded cathode particles without destroying the bulk phase, are promising energy-saving alternatives to traditional metallurgy processes that involve several steps and use large volumes of chemicals causing secondary pollution. Herein, we report a novel and scalable method for the direct electrochemical recycling of spent lithium iron phosphate (LFP) powder in a flow cell via redox mediation. In this method, pellets of spent LFP powder (S-LFP) placed in a tank are directly reduced and relithiated by a redox mediator dissolved in a Li-containing aqueous electrolyte, pumped from an electrochemical cell stack to the relithiation tank. Redox mediators transport charge to the S-LFP pellets from the electrochemical cell, where Li4Fe(CN)6 is oxidized and Li ions are supplied from a Li4Fe(CN)6-containing counter compartment through an ion-selective membrane. The consumption of the regenerating redox mediator solution is minimal via a closed-loop electrochemical regeneration reaction. Successful S-LFP regeneration using two redox mediators, with different energy demand processes, is confirmed by structural and electrochemical characterization.
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Dec 2025
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Diamond Proposal Number(s):
[40403]
Open Access
Abstract: Metal−organic gels (MOGs) and their derived aerogels (MOAs) offer an alternative to crystalline MOFs, combining the coordination-driven tunability with the flexibility, hierarchical porosity, and easy processability of sol–gel polymers. Their noncrystalline nature enables the integration of functional units without crystallization constraints, facilitating diverse uses, and drawing recent attention for photocatalytic applications. Herein we report the design of a new approach to prepare a titanium-based MOA synthesized via a two-step strategy involving a preformed titanium oxo-cluster ([Ti8O8(benzoato)16]), and a subsequent ligand exchange with benzene-1,3,5-tricarboxylato ligands. A combined chemical, microstructural, and NEXAFS analysis confirms the retention of Ti8 cluster and the presence of uncoordinated −COOH groups after meso-macroporous gel formation. Those enabled a subsequent homogeneous incorporation of single-atom site co-catalysts via coordination with Ru, Co, Ni, and Cu complexes bearing terpyridine, bipyridine, and phenanthroline N-ligands. Photocatalytic hydrogen evolution under 365 nm LED irradiation exhibited significant activity (110 μmol·g–1·h–1), which further increased upon functionalization. The MOAs functionalized with Ru- and Cu-terpyridine complexes showed the highest performance (167 and 164 μmol·g–1·h–1, respectively), surpassing even Pt-loaded analogues and highlighting the role of terpyridine in facilitating multielectron storage. The system also showed stable long-term performance up to 24 h.
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Dec 2025
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Abstract: The low-temperature performance of mixed-composition perovskite solar cells (PSCs) reflects the complex interplay among thermal effects, bandgap renormalization, and structural phase behavior. Temperature-dependent structural, optical, and electrical measurements reveal a maximum power conversion efficiency at 263 K, which coincides with the onset of the cubic-tetragonal phase coexistence. At this temperature, symmetry lowering is observed, accompanied by a split emission band and increased current–voltage hysteresis, consistent with structural heterogeneity. Device simulations show that any benefit from mixed-phase band alignment is conditional on effective interphase passivation. Consequently, the mixed phase is best described as a loss-minimum condition at well-passivated cubic–tetragonal interphases with stable collection. Our findings identify a narrow mixed-phase window in which phase coexistence couples to the optoelectronic response and enhances the device performance, providing fundamental insight into temperature-dependent structure–property relations in hybrid perovskites.
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Dec 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[36397]
Abstract: The widespread adoption of Li-ion batteries has created a pressing need for effective recycling strategies. A common approach involves producing “black mass”─a mixture of shredded electrode materials─followed by thermal treatment to simplify downstream recovery. Although current collectors (Al and Cu foils) are assumed to be physically separated before pyrolysis, industrial separation is often incomplete, leaving residual foil fragments that can chemically react with cathode materials. Here we investigate the influence of these foils on black mass pyrolysis using simplified model systems composed of pristine LiNi0.8Mn0.1Co0.1O2 and current collector fragments under inert, mildly oxidizing, and reducing atmospheres. Cu foils were found to form lithium copper oxides, LiCuO and Li2CuO2, previously unreported in the Li-ion battery recycling literature. Al foils produced γ-LiAlO2, Li5AlO4, and LiAl2(OH)7·2H2O. The two latter phases readily decompose to γ-LiAlO2, a compound that has been suggested to be detrimental for Li recovery due to its low solubility. We assess the leaching implications of these product phases, with particular attention to γ-LiAlO2, to establish that they readily dissolve in dilute H2SO4/H2O2 solutions, but can reduce Ni and Co leaching efficiency in more realistic black mass mixtures.
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Dec 2025
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E02-JEM ARM 300CF
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Xinjuan
Li
,
Zhao
Jiang
,
Si
Chen
,
Yi
Tang
,
Bofeng
Xue
,
Tianhao
Wu
,
Yang
Lu
,
Xavier
Moya
,
Akshay
Rao
,
Zhongzheng
Yu
,
Caterina
Ducati
Diamond Proposal Number(s):
[39081]
Open Access
Abstract: Perovskite quantum dots (PeQDs) offer high photoluminescence quantum efficiencies, precise spectral tunability, and solution-processability, making them promising for advanced optoelectronics. However, their structural and defect evolution under thermal stress remains poorly understood. Here, direct nanoscale insights are provided into temperature-driven phase transition and defect dynamics in CsPbBr3 PeQDs using high-resolution, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images, 4D STEM, and photoluminescence spectroscopy. Sub-ångström imaging at room temperature reveals inherent atomic features and octahedral tilting of the lead halide perovskite lattice in PeQDs, suggesting a pre-tilted, low-symmetry state before thermal perturbation. The cryogenic cooling induces a reversible orthorhombic-to-monoclinic phase transition, distinct from bulk perovskite behavior and accompanied by severe strain localization exceeding 20% at surfaces and grain boundaries. A controlled cryogenic post-synthesis treatment can effectively heal defects and improve radiative recombination, whereas prolonged cryo-treatment introduces irreversible structural degradation. These findings highlight the intrinsic structural flexibility of PeQDs and provide a scalable post-synthesis treatment method to optimize the stability and efficiency of QDs for various optoelectronic applications.
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Dec 2025
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Open Access
Abstract: Oxygen redox (OR) in Li1.2Ni0.13Co0.13Mn0.54O2 (LRNMC) and Na0.67Mg0.28Mn0.72O2 (NMMO) has been associated with the formation of embedded molecular O2 due to the appearance of their distinctive features in RIXS, while it is unclear whether OR also affects the oxygen left in the lattice. Here we use high-resolution oxygen K-edge resonant inelastic X-ray scattering (RIXS) at threshold excitation (527.5 – 529.5 eV) revealing lattice responses due to OR. We find that both cathodes show pronounced multiphonon progressions, which are either altered or activated upon charging. The first progression, with a fundamental energy loss ∼67-74 meV, matches the A1g lattice-oxygen mode observed by Raman spectroscopy, confirming its bulk origin. The second progression that exhibits a fundamental loss of ∼98 meV appears only at the highest state of charge and is resonant with the new pre-edge states at 527.5 eV. The latter mode emerges concurrently with the characteristic trapped-O2 RIXS signal and is strongly coupled to an occupied electronic band near the Fermi level, indicating that OR may not only contribute to the formation of molecular O2, but also perturbs lattice oxygen states, likely via polaron-forming oxidized lattice oxygen.
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Dec 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[34446]
Open Access
Abstract: Understanding the redox behavior and structural stability of aliovalent substituents in ionic conductors is critical, as their variable oxidation states can inadvertently introduce electronic conductivity and alter transport mechanisms under different atmospheric conditions. Here, we report the atmosphere-dependent redox behavior and local coordination of Mo in LaNb0.9Mo0.1O4.05, focusing on its influence on phase transition and transport properties, where the as-sintered LaNb0.9Mo0.1O4.05 was systematically annealed under pure O2, pure N2, vacuum (∼1.6 × 10–8 mbar), and 5% H2/N2 at 800 °C for different dwell times. Electron paramagnetic resonance (EPR) spectroscopy results demonstrate the emergence of Mo5+ under 5% H2/N2. In situ X-ray absorption near edge structure (XANES) measurements reveal the reversible redox behavior of Mo, where Mo5+ formed under 5% H2/N2 reoxidizes to Mo6+ upon exposure to static air, while complementary in situ extended X-ray absorption fine structure (EXAFS) analysis shows that the Nb coordination environment also transitions from prototypical LaNbO4 structure under reducing conditions back to the Mo-substituted LaNbO4 structure upon reoxidation. This change of the oxidation states of Mo could correspondingly alter the band structure of the sample, which further enhances charge transport: the sample annealed in 5% H2/N2 for 24 h exhibits a reduced activation energy and increased electronic conductivity. These results highlight a strong coupling among substituent redox flexibility, local structure, and transport properties, providing an understanding of tailoring the properties of ionic conductors through controlled redox environments.
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Dec 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[36598]
Open Access
Abstract: O3 phase NiFeMn- based layered transition metal oxides have attracted interest for positive electrode materials for Na-ion batteries. However, they generally suffer from challenges like phase transitions and Fe migration. Recently, the substitution of Ca into the Na layer, serving as a ‘pillar’, has proven to be an effective approach to overcome these challenges. Here, we systematically studied the composition-dependent Ca pillaring effect on the electrochemical performance and structure evolution of two O3 phase NiFeMn-based layered transition metal oxides. It is found that, although moderate Ca doping in high-Ni system - Na1-2xCaxNi0.25Mn0.25Fe0.5O2 (x = 0.00, 0.03) enhances cycling stability and reduces polarization, excessive doping compromises rate capability and does not effectively prevent Fe migration. Conversely, high-Mn system - Na1-2xCaxNi0.17Mn0.33Fe0.5O2 (x = 0.00, 0.04) exhibits a more robust and beneficial response to Ca incorporation, showing enhanced structural integrity, improved redox reversibility, and effective suppression of Fe migration. This study provides insights into the tunable chemical environments of transition metal oxides, thereby advancing the design of high-performance positive electrode materials and contributing to the development of next-generation sodium-ion batteries.
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Dec 2025
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B18-Core EXAFS
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Connor
Sherwin
,
Veronica
Celorrio
,
Alessandro
Difilippo
,
Katie
Rigg
,
Mark
Clapp
,
Armando
Ibraliu
,
Luke
Luisman
,
Thomas
Wakelin
,
Amber
Watson
,
Nikolay
Zhelev
,
Lucy
Mcleod
,
Christopher
Zalitis
,
Andrea E.
Russell
Diamond Proposal Number(s):
[35671, 10915, 30590, 33009]
Open Access
Abstract: Understanding the structural properties of iridium oxide electrocatalysts under operational conditions is critical for elucidating the structure–property relationships that enhance the catalytic activity for the oxygen evolution reaction. In this study, in situ X-ray absorption spectroscopy under realistic conditions was employed to investigate the potentiodynamic and time-resolved structural evolution of a commercial iridium oxide, alongside its fully hydrated and crystalline counterparts. Our findings reveal two distinct electrochemical regimes, a low potential plateau associated with a nonconductive Ir3+ state and a linear region where small potential variations induce reversible oxidation state and structural transformations. The structural changes were found to occur reversibly on the commercial material even after prolonged exposure to OER potentials. Notably, the hydrated IrOx exhibits extremely high OER activity, surpassing the commercial material by nearly an order of magnitude, yet it suffers from significant instability. In contrast, the crystalline IrO2 demonstrates poor activity as its catalytic performance appears to be confined to the surface. These findings highlight the critical role of hydration in modulating both activity and stability, offering valuable insights for the rational design of next generation iridium based OER catalysts.
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Dec 2025
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