I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[39324]
Open Access
Abstract: Fertilizers derived from ammonia (NH3) play a vital role in global food production, and ammonia is also emerging as a carbon-free fuel or hydrogen carrier. To facilitate the use of ammonia as an energy carrier, there is a need to develop catalysts that enable ammonia production under milder conditions than the current Haber–Bosch process. Industrially, high temperatures and pressures (>450 °C, >100 bar) are required, partly due to the need to operate at conditions where the iron oxide (Fe2O3) catalysts are reduced to the active Fe phase. Herein, we show that intimate contact between Fe2O3 nanoclusters and alkali metal hydrides (LiH, NaH, and KH), arising from their co-confinement in nanoporous carbon, leads to high ammonia production under mild conditions (∼250 °C and 10 bar), without prior reduction of the Fe2O3. The alkali metal hydrides show profound differences in catalytic activity due to the differences in their interaction/reactivity with Fe2O3 nanoparticles, as well as activation of N2. These results show that co-nanoconfinement of metal hydrides and transition metal oxides is a promising approach toward developing catalysts for low-temperature ammonia synthesis.
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Jul 2026
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B18-Core EXAFS
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Open Access
Abstract: Earth-abundant metal catalysts are important for future polymer production. Iron is both an earth-abundant and non-critical element and is attractive for catalysis. Here, a series of heterodinuclear catalysts incorporating Fe(III) with different s-block metals, M(I/II) = K(I), Na(I), Sr(II), Ba(II), an Fe(II)K(I) catalyst, and a monometallic Fe(III) catalyst are reported for the ring-opening copolymerization of cyclohexene oxide and phthalic anhydride to produce polyesters. The lead Fe(III)K(I) catalyst achieves a high turnover frequency of 3478 ± 51 h–1 (1:400:7000, [catalyst]0:[PA]0:[CHO]0, 140 °C) while retaining quantitative (>99%) polyester selectivity. Its performance is competitive with the best catalysts in the field. Using microscale calorimetry, the polymerization rate law, rate coefficients and transition state energies are determined. These data are rationalized by a dinuclear catalytic mechanism and allow for insight into the influence of varying catalyst structural features on the reaction enthalpy and entropy barriers. The results inform upon the physical origins of high catalytic activity and provide mechanistic insights useful for future catalyst design.
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Jul 2026
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[39378]
Open Access
Abstract: Realizing net-zero emissions demands the design of innovative and efficient catalysts for CO2 valorization. Herein, we report a core@shell-structured catalyst precursor, h-ZrO2@Cu1.3ZnAl1.6-LDH, in which layered double hydroxide (LDH) platelets are arranged around hollow zirconia spheres (h-ZrO2), maximizing the interfacial area between the active LDH component and zirconia promoter. The h-ZrO2@Cu1.3ZnAl1.6-LDH-derived catalyst efficiently converts CO2 into methanol, reaching space-time yields (STYs) comparable to commercial catalysts, despite a 54% reduction in Cu loading (0.59 gMeOH gcat−1 h−1 at 250 °C, 45 bar, H2/CO2 = 3, 18,000 mL g−1 h−1 weight hourly space velocity, WHSV). Reporting the STY on a per gram copper basis highlights the efficiency of the catalyst: h-ZrO2@Cu1.3ZnAl1.6-LDH is twofold more active than the commercial catalyst under the same conditions (2.7 vs 1.3 gMeOH gcat−1 h−1).
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May 2026
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B18-Core EXAFS
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Diamond Proposal Number(s):
[34632]
Open Access
Abstract: Understanding and tuning the local coordination environment of Fe−N4 macrocyclic catalysts are essential for advancing non-precious metal oxygen reduction reaction (ORR) electrocatalysis. Here, we present a comprehensive experimental and theoretical investigation of three structurally distinct Fe macrocycles, iron(tetraphenylporphyrin) chloride (FeTPP), iron(II) phthalocyanine (FePc), and iron aza-bridged bis-1,10-phenanthroline hexaaza-macrocycle (Fe(Phen2N2)), to unravel how bridging atom identity and coordination geometry impact ORR activity in alkaline media. These measurements identified FePc/CNT as the most active catalyst, followed closely by Fe(Phen2N2)/CNT, with FeTPP/CNT exhibiting the lowest performance. Density functional theory simulations further demonstrated that shorter Fe−N bonds and more electronegative bridging atoms correlate with weaker *OH adsorption and higher theoretical limiting potentials. Axial coordination can alter the adsorption energetics of ORR intermediates, thereby enhancing ORR activity. Together, these results highlight the critical influence on the ORR mechanism of macrocycle bridging atoms, coordination symmetry, and axial ligation, providing molecular-level insights to guide the rational design of Fe−N4 catalysts for alkaline fuel cell applications.
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May 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Diamond Proposal Number(s):
[41758]
Open Access
Abstract: NixFe1–xOyHz is the state-of-the-art catalyst for the oxygen evolution reaction (OER) in alkaline water electrolyzers; however, understanding the impact of Fe on the active sites, reaction mechanism, and consequently intrinsic activity has been under intense debate. In this work, operando UV–vis spectroscopy was used to investigate Fe-free NiOxHy and NiOxHy with Fe selectively incorporated onto the surface. At oxygen-evolution potentials, similar oxidized nickel states were present before and after the Fe incorporation, with negligible changes in their redox potentials. However, the discharge kinetics of the Ni states show a substantial acceleration after the introduction of Fe, consistent with an increase in OER kinetics upon Fe incorporation and formation of active Ni–Fe species. Using optical spectroscopy, we determined the intrinsic reaction time constant per surface Fe site is <0.1 s, which is 2 orders of magnitude faster than Ni sites not in proximity to surface Fe sites (∼10 s), and also an order of magnitude faster than Ni sites in pure NiOxHy (∼1 s). Consequently, we propose that the OER occurs via charge accumulation primarily on Ni centers in these catalysts, followed by hole transport to the surface Fe species where oxygen evolution occurs.
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Mar 2026
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[34566]
Abstract: Artificial metalloenzymes (ArMs) offer a versatile and evolvable platform to extend the biocatalytic repertoire. Here we report the assembly of an ArM resulting from supramolecular anchoring an N-heterocyclic carbene Au(I) complex into a de novo designed tandem repeat protein (TRP). We identified a variant that, compared to the free cofactor, led to a higher catalytic activity for the Au-catalyzed hydroamination of 2-ethynylaniline. Structure-guided mutagenesis of this variant improved the activity, resulting in a double mutant displaying up to 4-fold higher catalytic rates than the original TRP. Biophysical and crystallographic analysis revealed distinct cofactor binding poses, with single mutations reshaping the active site and correlating with improved catalytic performance. Importantly, the TRP scaffold imparted robustness, preserving catalytic activity under acidic conditions, in the presence of organic cosolvent, and at elevated temperatures, where the free cofactor was deactivated. This work highlights the potential of de novo designed proteins to harbor non-natural metal cofactors and points to design principles for stabilizing sensitive catalysts under chaotropic conditions.
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Mar 2026
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I15-1-X-ray Pair Distribution Function (XPDF)
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Danial
Farooq
,
Lucy
Costley-Wood
,
Sebastian
Stockenhuber
,
Antonis
Vamvakeros
,
Stephen
Price
,
Lisa
Allen
,
Jakub
Drnec
,
James
Paterson
,
Mark
Peacock
,
Daniel J. M.
Irving
,
Philip A.
Chater
,
Andrew M.
Beale
Diamond Proposal Number(s):
[30639]
Open Access
Abstract: The transition to net-zero emissions hinges on circular economy strategies that valorize waste and enhance resource efficiency. Among X-to-liquid (XTL) technologies, the Fischer-Tropsch (FT) process stands out for converting biomass, waste, and CO2 into hydrocarbons and chemicals, especially when powered by renewable hydrogen. Cobalt-based catalysts are preferred in FT synthesis due to their efficiency and CO2 tolerance, yet their catalytic performance is closely tied to their polymorphic structures─face-centered cubic (FCC), hexagonal close-packed (HCP), and stacking-faulted intergrowths thereof. HCP cobalt has been shown to exhibit high activity and selectivity for higher hydrocarbons and oxygenates, particularly when transformed into cobalt carbide (Co2C), which forms more readily at low H2/CO ratios. This study presents a quantitative analysis of cobalt polymorphs and stacking faults in Mn-promoted Co/TiO2 FT catalysts from in situ powder X-ray diffraction (XRD) data and X-ray Diffraction Computed Tomography (XRD-CT) data from spent catalysts in order to obtain a more complete correlation of structural features with catalytic performance. By modeling stacking fault probabilities using supercell simulations, the proportion of faulted FCC and HCP domains was determined across varying Mn loadings (0–5%). Increased Mn loading was found to decrease stacking faults in the FCC phase while increasing them in HCP, promoting the formation of HCP domains and ultimately Co2C under reaction conditions. Notably, the 3% Mn-loaded sample showed a marked rise in HCP content and Co2C formation, correlating with the highest observed alcohol and olefin selectivity. These findings highlight a critical structure–function relationship: Mn facilitates a transformation from FCC to HCP and then to Co2C, this final transition driven by similar stacking sequences and metal–support interactions. The findings show that Mn promotion not only stabilizes smaller Co particles and enhances its dispersion, but also modulates the distribution of Co polymorphs and stacking faults, leading to altered catalytic behavior. This highlights the importance of stacking fault characterization for optimizing FT catalyst design and performance, and suggests pathways to more efficient and selective carbon-neutral fuel production through engineered polymorphic and interfacial structures.
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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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E01-JEM ARM 200CF
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Naomi
Lawes
,
Igor
Kowalec
,
Sofia
Mediavilla-Madrigal
,
Kieran J.
Aggett
,
Louise R.
Smith
,
Malcolm
Dearg
,
Thomas J. A.
Slater
,
Eimear
Mccarthy
,
Herzain I.
Rivera-Arrieta
,
Matthias
Scheffler
,
David J.
Morgan
,
David J.
Willock
,
Andrew M.
Beale
,
Andrew J.
Logsdail
,
Nicholas F.
Dummer
,
Michael
Bowker
,
C. Richard A.
Catlow
,
Stuart H.
Taylor
,
Graham J.
Hutchings
Diamond Proposal Number(s):
[3104]
Open Access
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.
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Jan 2026
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B18-Core EXAFS
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Wenjie
Liu
,
Huibo
Zhao
,
Xianyue
Wu
,
Jianfeng
Wu
,
Lingjun
Chou
,
George
Dury
,
Wenting
Hu
,
Mikhail V.
Polynski
,
Arravind
Subramanian
,
Sergey M.
Kozlov
,
Wen
Liu
Diamond Proposal Number(s):
[34632]
Abstract: Understanding factors controlling product selectivity in CO2 hydrogenation remains a central research theme for catalytic CO2 utilization. Here, we report a composition-dependent selectivity anomaly in the In–Pd intermetallic series (viz., InPd2, InPd, In3Pd2), where In3Pd2 exhibits 100% CO selectivity via the reverse water–gas shift (RWGS) pathway, in sharp contrast to the high methanol selectivity achieved on other In-rich or Pd-rich metals or intermetallic compounds. Comprehensive characterization reveals that this anomaly arises from Pd enrichment on the surface of In3Pd2 IMC nanoparticles. The enriched Pd sites, modulated by In-to-Pd electron transfer, favor CO formation. In addition, the In-rich sites neighboring the Pd-rich islands facilitate rapid CO desorption. The resulting nanostructure on the surface of In3Pd2 IMCs renders an electronic interaction between In and Pd to promote CO formation and suppress C–H bond formation. This rationale is supported by both density functional theory (DFT) calculations and experimental evidence. These findings demonstrate that compositional control in intermetallic catalysts enables switchable CO2 hydrogenation selectivity and offers a rational approach to designing catalysts with tailored product distributions.
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Jan 2026
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