B18-Core EXAFS
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Diamond Proposal Number(s):
[34632]
Abstract: Polychlorinated aromatic hydrocarbons (PCAHs) in flue gas seriously threaten the environment and human health, and Ru-based catalysts exhibit efficient oxidation property for PCAHs removal. However, the current Ru catalysts either have high Ru loading/non-stable structure or are developed empirically whilst lack of design mechanism. Herein, a robust Ru single atom catalyst (0.5 Ru1/TiO2) was designed based on metal-support interaction for o-DCB (o-dichlorobenzene, a typical PCAHs) degradation, and it revealed significantly better oxidation activity with T50 = 207.4 °C and T90 = 243.5 °C than its contrast with weak metal-support interaction (0.5 RuNP/TiO2, T50 = 247.4 °C, T90 > 300 °C). In addition, 0.5 Ru1/TiO2 exhibited much better chlorine resistance stability, maintaining >90% o-DCB conversion for 700 min versus∼70% on 0.5 RuNP/TiO2. The superior performance of 0.5 Ru1/TiO2 was attributed to its stronger metal-support interaction between Ru and TiO2, verified by H2-TPR, which offered higher active oxygen species (22.4%), more Lewis acid (0.675 mmol/g) and higher exposed Ru ratio (> 90.0%) than 0.5 RuNP/TiO2 (15.0%, 0.068 mmol/g, 28.6%, respectively). The above properties can not only enhance o-DCB adsorption/activation and weaken its Csingle bondCl bonds but also favor partial/deep oxidation and remove deposited chlorine on 0.5 Ru1/TiO2, proved by in situ FT-IR. Moreover, notable higher water resistance under different water vapor and applicability under varied pollutant concentration were observed on the robust Ru1/TiO2. This work reveals insightful function-property study on Ru single atom catalysts for PCAHs oxidative removal.
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May 2026
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[35970]
Open Access
Abstract: We have determined the pressure dependence of the ratio S6+/(S2-+S6+) in silicate melts by measuring the effects of pressure on the concentrations of sulfide (S2-) and sulfate (SO42-) species at known fugacities of sulfur and oxygen. For S2- we controlled f(S2) using mixtures of Ag and Ag2S with oxygen fugacity held at the CCO buffer. For S6+ we measured molten CaSO4 solubility as a function of pressure. We define sulfide capacity and sulfate capacity from the S2- and S6+ contents of the melt as (Fincham and Richardson, 1954): and .
The dependences of and on pressure were found, with P in bars and T in K, to be:
and . The negative pressure dependences are due to the differences in partial molar volumes between sulfide S2- and oxide O2– species and sulfate SO42 -and oxide O2– which we calculate to be ∼ 10.7 cm3/mol and ∼ 31.6 cm3/mol respectively. These are similar to the differences in volumes between CaS and CaO (10.96 cm3/mol) and CaSO4 and CaO (29.2 cm3/mol).
We used these and equations to calculate the pressure dependence of the “crossover” oxygen fugacity at which S2- transforms to S6+ in silicate melts of different composition. The crossover is shifted in absolute f(O2) by + 0.25 log units or, relative to FMQ, by −0.41 log units as pressure is increased from 1 bar to 1 GPa at 1400 °C. This demonstrates that the effect of pressure on sulfur oxidation state is small and may be neglected for many purposes. The pressure dependence of the S2-—S6+ crossover means that there would be some electron exchange between Fe2+ and S6+ during decompression in a closed system (S2-+8Fe3+ = S6++8Fe2+). The effect is small, but largest in melts which start at oxygen fugacities close to and above FMQ and would, for a basalt containing 1500 ppm S lead to an increase in oxygen fugacity of 0.4 to 0.5 logf(O2) units during decompression from 1.5 GPa to 1 bar.
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Mar 2026
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B18-Core EXAFS
I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[32893, 14239]
Open Access
Abstract: Fluorination of the n = 2 Ruddlesden–Popper oxide, La3Ni2O7, with polyvinylidene fluoride yields La3Ni2O5F4, a phase in which fluoride ions have been inserted into interstitial sites in the Ruddlesden–Popper framework and also exchanged with the oxide ions residing on apical anion sites. Reaction with LiH at 190 °C reduces La3Ni2O5F4 by extracting interstitial fluoride ions. The resulting phase, La3Ni2O5F3, adopts a structure described in space group Pbcm in which the fluoride ions in the half-filled interstitial layer are arranged in chains parallel to the y-axis, and the NiO5F octahedra adopt an a–a–c+/–(a–a–)c+ tilting pattern. Further reduction with LiH at 250 °C converts La3Ni2O5F3 into La3Ni2O5F, a Ni1+ phase which adopts a T′-structure consisting of double infinite-sheets of apex linked NiO4 squares, stacked with LaOF fluorite-type layers. Magnetization and neutron diffraction data indicate La3Ni2O5F3 adopts an antiferromagnetically ordered state below TN = 225 K, while magnetization data from La3Ni2O5F exhibit a broad maximum centered at 75 K, suggestive of antiferromagnetic order.
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Feb 2026
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[31906, 39961]
Open Access
Abstract: Mercury (Hg) is a global environmental concern due to its microbial conversion to methylmercury (MeHg), a potent neurotoxin that bioaccumulates in food webs and poses risks to ecosystems and human health. Thiol functional groups (RSH) play an important role in controlling Hg(II) speciation and bio-uptake in methylating bacteria, yet the spatial distribution and density of these thiols within cells remain largely unknown. We isolated subcellular fractions of the Hg methylating bacterium Geobacter sulfurreducens in the exponential growth phase, and used Hg LIII-edge EXAFS (Extended X-ray Absorption Fine Structure) to quantify thiols in the extracellular medium, inner and outer membranes, periplasm and cytoplasm. The whole-cell thiol content was determined to be 1.3 × 10−10 μmol cell−1. The inner membrane contributed 7.1 × 10−11 (53%), the outer membrane 1.2 × 10−11 (9%), the periplasm 3.6 × 10−11 (27%) and the cytoplasm 1.5 × 10−11 μmol cell−1 (11%). The extracellular fraction contributed an additional 5.7 × 10−11 μmol cell−1, corresponding to 30% of the thiols of the cell culture. Local thiol density (thiols normalized to TOC in individual compartment, RSH/TOC, μmol g−1 C) was 36, 450, 140, 600 and 29 μmol g−1 C in the cytoplasm, inner membrane, periplasm, outer membrane and extracellular fractions, respectively. EXAFS analyses demonstrate Hg-thiolate coordination across all compartments, with Hg-O/N bonding and elemental Hg0 formed at higher Hg loadings. In the periplasm, Hg-disulfide and traces of β-HgS were detected. The high thiol density at the membranes, relative to other compartments, may imply they have an important role in the retention and internalization of Hg(II). Periplasmic thiols may modulate Hg(II) transfer between membranes, and cytoplasmic thiols may regulate the intracellular availability of Hg(II) for methylation. This work provides the first compartment-resolved quantification of thiol abundances and densities in a model Hg-methylating bacterium at subcellular level, offering a mechanistic framework for understanding the speciation, bioavailability, and subcellular transformation of Hg(II) with relevance for other soft metals (e.g., Cd, Pb, Zn, Ag, and Cu).
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Feb 2026
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B18-Core EXAFS
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Yingxiang
Zhao
,
Yingjie
Zhao
,
Xinyue
Zhou
,
Haiwei
Guo
,
Qiqi
Yin
,
Yutao
Jiang
,
Haiyan
He
,
Na
Liu
,
Gengbo
Ren
,
Christopher M. A.
Parlett
,
Changzhi
Li
Diamond Proposal Number(s):
[34632]
Abstract: M–N–C single-atom catalysts (SACs) represent promising candidates owing to their atomically dispersed active sites and tunable catalytic properties and have shown broad potential in various catalysis reactions. However, the mechanisms and true active sites involved in lignin conversion, particularly oxidative depolymerization, remain unclear. Herein, a Ru–N–C SAC with a well-defined configuration, including coordination environment and coordination number, was synthesized via a straightforward ball-milling method for lignin oxidation. The Ru–N–C SAC prepared with 12 h of ball milling demonstrated high catalytic performance in the oxidative depolymerization of various β-O-4 model compounds and diverse lignin feedstocks. Structural analysis via X-ray absorption spectroscopy demonstrated that the Ru–N4 motif constitutes the predominant coordination environment in Ru–N–C, which is regarded as the primary active site in activating O2 into superoxide radicals, as confirmed by free-radical quenching experiments and electron paramagnetic resonance analysis; meanwhile, it also served as a basic site in polarizing Cβ–H bonds in β-O-4 that favored C–O/C–C bond cleavage, which was disclosed by CO2 temperature-programmed desorption and electron localization function analysis. The critical role of Ru–N4 in the activation of O2 and C–O/C–C bond cleavage was further confirmed by density functional theory calculation, which indicated that the Ru–N4 center exhibits strong adsorption toward both the O2 and β-O-4 linkages. This work provides a deep understanding on the active sites within Ru–N–C SACs for lignin oxidative cleavage and offers great potential on the rational design of next-generation SACs in biomass valorization.
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Feb 2026
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B18-Core EXAFS
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Fei
Guo
,
Manxi
Gong
,
Longxiang
Liu
,
Bochen
Li
,
Ruwei
Chen
,
Mengjun
Gong
,
Wei
Zong
,
Jianuo
Chen
,
Qi
Li
,
Jing
Li
,
Yunpeng
Zhong
,
Zeyi
Zhang
,
Jianrui
Feng
,
Rhodri
Jervis
,
Guanjie
He
Diamond Proposal Number(s):
[34632]
Open Access
Abstract: Platinum–transition metal (PtM) alloys are among the most promising oxygen reduction reaction (ORR) catalysts, yet their practical deployment in proton-exchange membrane fuel cells (PEMFCs) is hindered by transition-metal dissolution, particle coarsening, and insufficient durability. Moreover, conventional alloying or intermetallic ordering strategies often aggravate these issues by inducing severe nanoparticle aggregation and instability. Here we report a controllable alloying–dealloying strategy to construct PtNi nanoparticles confined in an N-doped carbon framework (Pt1Ni1-x@Nix_NC). Ammonia-assisted dealloying produces a Pt-rich shell with an alloyed core, while the N-doped carbon anchors the released Ni atoms form Ni–N/C moieties, thereby suppressing agglomeration and strengthening metal–support interactions. This coordination–support coupling optimizes Pt 5d orbital occupation, weakens oxygen adsorption, and accelerates ORR kinetics. Consequently, Pt1Ni1-x@Nix_NC exhibits a half-wave potential of 0.932 V and an ultrahigh mass activity of 2.028 A mgPt−1, which is 8.75-fold higher than commercial Pt/C and among the best values reported to date for PtNi-based catalysts. Remarkably, it shows only a 6 mV half-wave potential loss after 30,000 cycles, demonstrating exceptional durability. In PEMFCs, the fuel cell delivers 975 mW cm−2 peak power density and retains 91.9% of initial performance, underscoring a generalizable approach for designing durable, high-performance low-PGM catalysts for next generation PEMFCs.
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Feb 2026
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I10-Beamline for Advanced Dichroism - scattering
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Diamond Proposal Number(s):
[35696]
Open Access
Abstract: Cobalt ferrite nanoparticles are a benchmark among low-to-medium energy alternatives to rare-earth permanent magnets, although their intrinsic behavior is often obscured by surface disorder, finite-size effects, and superparamagnetic relaxation. Here, we overcome these limitations by synthesizing large, highly crystalline cobalt-doped ferrite nanoparticles (≈ 25 nm), which remain blocked at room temperature and thus provide a clean platform to disentangle the fundamental role of cobalt in the spinel lattice. By systematically varying the cobalt content, we reveal a complex interplay between cation distribution, oxygen vacancy formation, and magnetic response. Structural and compositional analysis confirms predominant Co2+ occupancy at octahedral sites, accompanied by a redistribution of Fe2+/Fe3+ and non-linear oxygen vacancy generation. We find that while saturation magnetization is largely governed by defect chemistry, the coercivity and effective anisotropy are primarily controlled by cobalt incorporation and saturate at intermediate compositions. In contrast, thermomagnetic analysis reveals an anomalous evolution of magnetization at intermediate temperatures for specific cobalt contents. This behavior is consistent with a change in the anisotropy landscape, suggestive of a growing contribution from higher-order anisotropy terms, rather than a simple uniform increase in magnetocrystalline anisotropy. These results indicate that cobalt doping tunes the balance between different anisotropy contributions in a composition- and temperature-dependent manner. Overall, our findings highlight the subtle interplay between cation distribution, anisotropy landscape, and thermal stability in spinel ferrites, providing fundamental insight for the design of high-coercivity rare-earth-free nanomagnets.
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Feb 2026
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I10-Beamline for Advanced Dichroism - scattering
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Diamond Proposal Number(s):
[36197]
Abstract: Heterostructures composed of heavy metal and van der Waals (vdW) magnets serve as platforms to investigate magnetotransport properties, enabling the electric readout of the spin-flop transition in the vdW antiferromagnet. We investigate the spin and orbital contributions to magnetism in Pt/exfoliated multilayer CrPS4 heterostructure using the synchrotron-radiation based x-ray magnetic circular dichroism technique measured in the total electron yield (TEY) mode. The TEY detection, with probing depth of 5–10 nm, mainly reflects the interfacial magnetic behavior near the Pt/CrPS4 boundary. A spin-flop transition appears near 0.7 T in both the CrPS4 single crystal and the Pt/CrPS4 heterostructures. The total Cr moment remains ∼2 μB/f.u. in both systems at 14 T and 6 K. In Pt/CrPS4, the orbital moment is strongly modulated by Pt, as manifested in the enhancement from ∼0.1 μB/f.u. in CrPS4 to ∼0.5 μB/f.u. in Pt/CrPS4, an effect attributable to the strong spin–orbit coupling with Pt. At 25 K, the total Cr moment reduces to ∼1.1 μB/f.u. in both systems. The Cr orbital moment in CrPS4 remains low ∼0.1 μB/f.u., whereas in Pt/CrPS4 it remains high ∼0.5 μB/f.u. These findings provide qualitative evidence of robust spin–orbit coupling and orbital hybridization at Pt/CrPS4 interface, and highlight the potential of heavy metal/vdW antiferromagnet heterostructures for spin-orbitronic device applications.
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Feb 2026
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B18-Core EXAFS
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Yuan
Liao
,
Yang
Fu
,
Fengzhan
Sun
,
Yuanshen
Wang
,
David C.
Lloyd
,
Zhiyong
Zhao
,
Zipei
Wan
,
Federico
Grillo
,
Arvydas
Ruseckas
,
Edward
Ogugu
,
John T. S.
Irvine
Open Access
Abstract: As the global energy landscape shifts to a green hydrogen economy, efficient and stable visible-light photocatalysts are increasingly central to optimizing solar-to-hydrogen conversion. Here, a Sr-site-deficient perovskite photocatalyst (R-Pt/Sr0.95Ti0.9Cr0.1O3-δ) was synthesised by a solid-state method, followed by Pt impregnation and hydrogen reduction post treatment. The introduction of A-site deficiency effectively tunes the band structure and facilitates hydrogen evolution, doubling activity compared to stoichiometric analogs. Besides, A-site deficiency reduces overall cation charge and promotes Cr4+ formation. Through spectroscopy and thermal analysis, Cr4+ was identified in the Sr0.95Ti0.9Cr0.1O3-δ perovskite, revealing unexplored oxidation state dynamics. Upon reduction, Cr4+ converts to Cr3+, creating oxygen vacancies and eliminating hole-trap sites. The resulting synergistic active sites greatly boost photocatalytic hydrogen evolution. Specifically, the R-Pt/Sr0.95Ti0.9Cr0.1O3-δ achieved 120.46 μmol/gcat/h under full spectrum and 68.66 μmol/gcat/h under visible light (λ ≥ 420 nm), representing twice and 5 times enhancements relative to stoichiometric R-Pt/SrTi0.9Cr0.1O3-δ and unreduced Pt/Sr0.95Ti0.9Cr0.1O3-δ in visible light separately. This work demonstrates that combining A-site engineering and valence-state modulation provide a helpful strategy for designing high-performance visible-light photocatalysts.
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Feb 2026
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[34350]
Open Access
Abstract: Deep-sea sediments hold large quantities of critical rare earth-elements and yttrium (REY) sequestered in nanoparticulate biogenic fluorapatite (Ca5(CO3)x(PO4)3−xF1+x). Understanding their enrichment processes and improving recovery and mineral processing methods require atomic-scale information about their chemical form, but it is difficult to obtain. Here, we use novel high-energy-resolution fluorescence-detected extended X-ray absorption fine structure (HERFD-EXAFS) spectroscopy to elucidate the local structure of gadolinium (Gd) in the highly enriched REY deposit from the Clarion–Clipperton fracture zone (CCFZ) in the Pacific Ocean. Our findings reveal that Gd is neither incorporated into the apatite structure nor precipitated alongside Ce in a Ce–PO4 precipitate. Instead, it is bound at short-range distances to Ca and PO4 in a defective apatite-type bonding environment within an amorphous matrix that encases fluorapatite nanocrystals. Density functional theory (DFT) suggests that Gd and Y, whose atomic fraction is ten times higher than that of Gd, are not dispersed throughout the amorphous matrix, but are likely segregated at medium-range distances. The entrapment of Ce, Gd, and Y within an amorphous matrix explains, at the microscopic level, why REY can be easily recovered through straightforward acid leaching. This is due to the intrinsic instability of disordered atomic structures compared to crystalline phases. This research highlights the complementarity of HERFD-EXAFS and DFT calculations for atomic-scale analysis of trace elements in complex natural matrices. It establishes a basis for their use across diverse terrestrial and marine materials.
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Feb 2026
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