I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[23269]
Abstract: Lignin is a sustainable alternative to petroleum as a feedstock for the chemical industry. Emergent strategies for lignin valorization involve tandem processes in which biomass is chemo-catalytically fractionated, followed by bioconversion of the depolymerized lignin by microbial cell factories. A rate-limiting step in this bioconversion is O-demethylation of the lignin-derived monomers. The reductive catalytic fractionation of hardwood biomass generates high yields of two classes of monomers: 4-alkylguaiacols and 4-alkylsyringols. The former are O-demethylated by AgcA, a cytochrome P450, and AgcB, the cognate reductase, but there are no known enzymes that convert the latter. To develop a biocatalyst that can efficiently transform these monomers, we studied and rationally engineered AgcAB. A 1.82 Å resolution crystal structure of AgcAEP4 from Rhodococcus rhodochrous EP4 in complex with 4-ethylguaiacol identified residues Leu78, Ala293, and Phe166 as potential specificity determinants. Substitution of Ala293 and Leu78 decreased the specificity of AgcAEP4 for alkylguaiacols. Substitution of Phe166 yielded a variant that bound 4-propylsyringol but did not transform it. In contrast, the corresponding variant in the Rhodococcus aromaticivorans RHA1 homologue, AgcARHA1 Y166A, catalyzed the O-demethylation of both methoxy groups of 4-propylsyringol with a kcat/Km of 8500 M–1 s–1 for the first O-demethylation, nearly 7-fold higher than WT AgcARHA1. Engineering RHA1 to express the variant yielded a strain that transformed 4-propylsyringol and 4-propylguaiacol simultaneously. Moreover, the engineered strain converted some of the 4-propylsyringol to pentanoyl-CoA, consistent with catabolism via the meta-cleavage pathway that catabolizes 4-alkylguaiacols. Exometabolomics validated the conversion of 4-propylsyringol via this pathway and identified O-demethylation and extradiol ring cleavage as bottlenecks for its transformation. These studies improve our understanding of a critical lignin-degrading enzyme system and significantly advance the development of a biocatalyst to convert these monomers.
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Jul 2026
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Open Access
Abstract: The global transition from a coal-based energy economy to a green hydrogen economy, together with the demand for energy utilization efficiency, has intensified interest in ammonia as a carbon-free hydrogen energy carrier which is capable of storing and transporting renewable energy at scale. Efficient regeneration of hydrogen through thermal ammonia decomposition, enabled by advanced downstream technologies such as membrane reactors and purification systems, offers a techno-economically mature and evolving pathway. However, achieving low-temperature, energy-efficient ammonia decomposition remains a fundamental challenge. At the heart of this challenge lies the rational design of heterogeneous thermocatalysts capable of overcoming intrinsic kinetic limitations. Through critical examination of the vast research on catalyst systems and activity studies, we identify that tailored metal-support systems often give rise to multiple reaction pathways that govern the overall kinetics. To scientifically elucidate the origins of enhanced catalytic performance, the precise understandings on the nature of active sites and their coordination environments is the core. This requires precise identification of catalytically relevant sites, rigorous correlation between structure and reactivity, and operando-level insights into dynamic phase evolution. In this review, we reframe ammonia decomposition catalysis through the lens of active-phase chemistry. Based on our current understanding of active centres across different catalyst categories, we highlight strategies for rational catalyst design grounded in active phases and coordination environment. We further discuss advanced characterization methodologies capable of tracking active sites and unravelling their specific mechanistic contributions.
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Jun 2026
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I07-Surface & interface diffraction
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Olivia
Gough
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Katherine
Trinkaus
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Pascal
Kaienburg
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Zhenlong
Li
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Andrea E.
Lauritzen
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Jonathan
Rawle
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Hugo
Norris
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James
Hilfiker
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Joel
Smith
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Alessandro
Veneri
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Gregory
Su
,
Moritz
Riede
Diamond Proposal Number(s):
[30773, 32922]
Abstract: The microstructure of organic small molecule (SM) layers in organic solar cells (OSCs) strongly influences device performance by impacting light absorption, charge transport, and recombination. We demonstrate that ellagic acid (EA), a naturally derived templating layer, induces substantial morphological and thus optoelectronic changes in the vacuum thermally evaporated (VTE) donor molecule DCV5T-Me(3,3). Using in situ grazing incidence wide-angle X-ray scattering (GIWAXS) during thin film deposition in the purpose-built MINERVA VTE chamber at Diamond Light Source, we show that a 5 nm EA layer reorients DCV5T-Me from an edge-on to a face-on molecular packing motif. This templating effect persists for up to around 90 nm of film thickness.
Through UV-vis spectrophotometry and photoluminescence (PL) spectroscopy, we observe a shift towards H-aggregation and decreased light absorption in the donor molecule with the EA template. Atomic force microscopy (AFM) shows that the donor morphology changes as a function of thickness from the donor-templating interface. In DCV5T-Me(3,3):C60 bulk heterojunction devices, the EA layer helps retain donor crystallinity and enhances short circuit current (J
), despite the lower absorption. Maximum power conversion efficiency in our devices is achieved with a 5 nm templating layer, which provides sufficient structural templating while maintaining partial interfacial contact for efficient charge extraction. We hypothesise that the improvement in J
is likely driven by enhanced charge carrier dynamics due to the orientation change, shift toward H-aggregation, and change in growth mode.
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Jun 2026
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B18-Core EXAFS
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Diamond Proposal Number(s):
[37966]
Open Access
Abstract: With the ongoing interest in developing more stable and versatile catalysts for CO2 hydrogenation to methanol, molybdenum sulfide (MoS2) has been recently proposed as an alternative material. However, in its bulk state, CO2 hydrogenation over MoS2 typically favors methane formation. In this work, a wet impregnation method is applied for the production of ZnS-supported MoS2, as confirmed by characterization via X-ray Diffraction, Raman and X-ray Photoelectron Spectroscopy. In contrast with the negligible methanol production shown by the pure MoS2 reference, 2% MoS2/ZnS presents a methanol selectivity of 78% at a CO2 conversion of 2.3% under the mild reaction conditions of 200 °C and 20 bar. Density Functional Theory and Transmission Electron Microscopy suggest that the improved catalytic activity arises from an even dispersion of few-layer MoS2 with exposed basal plane sites at the ZnS surface, an arrangement possibly enabled by the structural similarity and the shared S atoms between 2H-MoS2 and W–ZnS phases. This hypothesis is strengthened by the comparison with the reference sample consisting of ZrO2-supported MoS2 sample, in which more agglomerated MoS2 particles resulted in a lower and less selective methanol production. Moreover, in situ X-ray absorption spectroscopy and H2 temperature-programmed reduction suggest further evidence of a MoS2/ZnS interaction during the H2 pretreatment, which may promote not only the expected formation of S-vacancies but also a partial reconstruction of MoS2 given the close contact and sharing of S atoms with the ZnS support.
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Jun 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Xin
Zhang
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Qiyun
Wang
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Qi
Zhang
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Haoyin
Zhong
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Chao
Wu
,
Baorui
Jia
,
Junchen
Yu
,
Ke-Jin
Zhou
,
Yuanjie
Li
,
Yong-Wei
Zhang
,
Zhi Gen
Yu
,
Shibo
Xi
,
Xiaopeng
Wang
,
Junmin
Xue
Diamond Proposal Number(s):
[35048]
Open Access
Abstract: Introducing oxygen redox chemistry into cobalt oxyhydroxide effectively enhances catalytic activity by enabling direct O-O coupling, thereby bypassing the rate-limiting *OOH step in the conventional adsorbate evolution mechanism. However, the key challenge is to preserve the accessibility of non-bonding oxygen states while maintaining cobalt-oxygen covalency. Here we show that light irradiation triggers ligand-to-metal charge transfer in sulfur-treated cobalt oxyhydroxide (S-CoOOH), generating non-bonding oxygen states. These states then couple with adjacent ones to form direct O-O bonds. Through this way, the sulfur-treated sample performs enhanced OER activity under light, achieving an overpotential of 194 ± 3 mV at 10 mA cm−2, which is 41 mV lower than in the dark. Further analysis reveals that light-induced oxygen redox activity is confined to the edge of catalyst. This activity originates from electron transitions from (M-O) to non-overlapping regions of Co 3 d and 4p orbitals, driven by high-spin Co3+ at the edge. This work highlights the critical role of light in inducing non-bonding oxygen states in transition metal-based catalysts and guides the development of oxygen-redox electrocatalysts.
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Jun 2026
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B18-Core EXAFS
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Diamond Proposal Number(s):
[37961]
Open Access
Abstract: In the present work, we report the exsolution of CoFe nanoalloy nanoparticles from Co and Fe co-doped lanthanum aluminate perovskite oxide, LaAl0.90Co0.05Fe0.05O3, and assess the perovskite oxide as an oxygen reduction reaction (ORR) electrocatalyst. We optimized both intrinsic and extrinsic material properties of perovskites to achieve good electrocatalytic performance in the kinetic and mass-transfer controlled region. Firstly, we demonstrated that the near surface segregation of B-site cation (Co) under reducing environment at low temperature (at 500 °C), believed to represent the initial stage of exsolution, led to high ORR activity in the mass-controlled region, with specific and mass activities of 4.9 mA/cm2 and 37.5 A/g (@0.4 V versus RHE), respectively. Secondly, reducing the particle size of perovskite oxide increased surface exposure to the reducing environment promoting the CoFe nanoalloy particle exsolution. The results demonstrate that cation enrichment in subsurface region, near grain boundaries contributes more effectively to ORR activity than exsolution in the form of nanoparticles in this perovskite oxide composition. Nevertheless, achieving fast charge transfer-kinetics without the use of precious metals still remains a challenge with lanthanum aluminates, as indicated by onset potentials of 0.84 V and 0.81 V (versus RHE) for the pristine and reduced perovskite oxide, respectively. Notably, impregnation of perovskite oxide with 0.2 wt. % Pt followed by heat treatment in reducing atmosphere at 500 °C increased the onset potential to 0.9 V. Overall, this study suggests that non-precious metal-doped lanthanum aluminate, LaAl0.90Co0.05Fe0.05O3, exhibits strong electrocatalytic activity and is further enhanced through impregnation treatment.
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Jun 2026
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B18-Core EXAFS
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Diamond Proposal Number(s):
[19850]
Open Access
Abstract: Integrating urea electrolysis into wastewater treatment systems represents a promising strategy to couple hydrogen production with environmental remediation. Nickel-based materials are among the most efficient non-precious catalysts for the urea oxidation reaction under alkaline conditions, yet Ni scarcity and its potential toxicity call for more sustainable alternatives. After demonstrating that Ni hydroxide recovered from wastewater is a good urea oxidation reaction catalyst, in this work, we report a fundamental and systematic study about urea oxidation reaction catalysts based on manganese-doped nickel hydroxide obtained through a synthesis route that mimics Ni recovery from wastewater to enhance the urea oxidation reaction performance. Thus, it offers both catalytic performance and circular-material benefits. A comprehensive characterization of the Ni(OH)2-based materials by experimental techniques, such as X-ray diffraction, scanning electron microscopy, X-ray absorption, and X-ray photoemission spectroscopy, combined with DFT theoretical calculations has revealed that Mn incorporation modifies the hydroxide structure, introduces ions in the +3 oxidation state, and promotes the formation of catalytically active NiOOH species. Mn dopants induce a favorable electronic effect through an indirect participation in the urea oxidation reaction mechanism involving oxidation state variation but not direct chemical bond formation. The reaction intermediates are in part different from those reported in previous literature. At a given potential, Mn doping enhances the overall urea oxidation rate, resulting in increased hydrogen evolution at the cathode. These findings point to a novel mechanistic understanding of the Mn-dopant role through its ability for an easier change to higher oxidation states than Ni ions, which reflects in a more favorable energetics of NiOOH formation and an improved urea oxidation reaction catalysis based on circular earth-abundant elements.
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Jun 2026
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E01-JEM ARM 200CF
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Emerson C.
Kohlrausch
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Christopher
Leist
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Gazi N.
Aliev
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Mohsen
Danaie
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Matthew
Young
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Madasamy
Thangamuthu
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Yifan
Chen
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William J.
Cull
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Wolfgang
Theis
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Ute
Kaiser
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Andrei N.
Khlobystov
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Jesum
Alves Fernandes
Diamond Proposal Number(s):
[37379, 38763]
Abstract: Understanding how catalytically active sites emerge and evolve under working conditions is a fundamental challenge that limits the rational design of heterogeneous catalysts. Here, we directly visualize the transformation between alloyed PtNi and phase-separated Pt-NiO nanoclusters during hydrogen evolution. Using in situ low-voltage aberration-corrected electron microscopy, with the electron beam serving as both the stimulus and probe, we track the formation of active sites under low-water-vapor conditions. PtNi nanoclusters were assembled with controlled mixing of the atoms, resulting in two distinct configurational entropy states. Under reaction conditions, the transformation of bimetallic nanoclusters shifts from an entropically stabilized alloy to an enthalpically favored phase-separated configuration, controlled by oxygen availability and by a critical nucleus size. The atomic dynamics observed in real space correlate directly with catalytic performance, where the low-entropy Pt-NiO state achieves a record hydrogen evolution mass activity of 11.1 A/mgPt due to a high density of interfacial sites that promote water dissociation on NiO and efficient hydrogen adsorption on Pt atoms.
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Jun 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Open Access
Abstract: Anion exchange membrane water electrolysis (AEMWE) represents a promising technology for green hydrogen production. Although numerous efforts have been devoted to optimize the anode catalysis by structural and chemical modulation, the effectiveness of such strategies in enhancing stability remains limited. Herein, we propose a cerium-induced double-shelled structure formation strategy that modulates the electrode/electrolyte interfacial microenvironment through spatial configuration engineering, effectively suppressing anodic corrosion. Mechanistic studies revealed that the associated nanospace enrichment effect increased the coverage of surface hydroxide ion (OH−) species, thereby enhancing the local alkalinity at the material surface and effectively suppressing ion leaching. The double-shelled cerium dioxide (CeO2)/lanthanum cobaltite (LaCoO3)-10% catalyst demonstrated outstanding performance in the AEMWE device, achieving an industrial-relevant current density of 3 amperes per square centimeter at 1.88 volts. Furthermore, the catalyst exhibited exceptional long-term stability exceeding 2000 hours under simulated industrial conditions. Our findings underscore the importance of engineering the physical spatial configuration to regulate the interfacial microenvironment, offering a strategy to address the corrosion degradation of anode catalysts.
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Jun 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
E01-JEM ARM 200CF
E02-JEM ARM 300CF
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Diamond Proposal Number(s):
[29340]
Open Access
Abstract: Ruthenium oxide is a well-known electrocatalyst for water splitting. Despite many advantages, the reaction mechanism and the structure changes of ruthenium oxide are unclear during catalysis, and the catalytic efficiency of ruthenium oxides remains a concern. In this paper, a needle-shaped copper substrate was synthesized, and the performance of RuOx was optimized. Reversible in situ Raman signals were found during the reaction process, which confirmed from the reversible surface reconstruction of RuOx. Density Functional Theory calculations found that the actual catalytic species is Ru(II)O. A detailed reaction mechanism of the Volmer step on the surface of ruthenium oxide was proposed based on the findings. The results indicate that the needles can lower the overpotentials of RuOx. At a current density of 10
, the overpotential of RuOx@ndl. was 68% lower than that of RuOx@b. f., which is much lower than the overpotential of commercial Pt(20wt.%)/C. This research provides a fundamental understanding of ruthenium oxide's reaction mechanism and gives insight into the design of the hydrogen evolution reaction catalysts.
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Jun 2026
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