B18-Core EXAFS
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Abstract: Industrial W-based olefin metathesis catalysts use silica as the support and generally show low activities. This is due to the difficulty in dispersing W species and in maintaining the structural integrity of W active centers on the silica surface. These catalysts also have poor W redox kinetics and slow olefin adsorption at reaction temperatures, which prohibits high reaction rates. Here, for the first time, we systematically demonstrate the dramatic multiple contributions from zeolite Y to the overall catalytic activity when it is used as the catalyst support. The high surface area and porous nature of zeolite Y can provide the isolation, immobilization, and confinement of W active centers. Isolated W active centers in zeolite Y show faster redox kinetics, which is crucial for olefin metathesis. Zeolite Y also facilitates rapid adsorption and isomerization of olefin substrates by its Brønsted acid sites for synergetic catalysis with W active centers.
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Jun 2026
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I11-High Resolution Powder Diffraction
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Jiaying
Mo
,
Lingling
Zhai
,
Alex W.
Robertson
,
Chiu C.
Tang
,
Sarah J.
Day
,
Simson
Wu
,
Lu
Chen
,
Tsz Woon Benedict
Lo
,
Molly Meng-Jung
Li
,
Shu Ping
Lau
,
Xin-Ping
Wu
,
Yiyang
Li
,
Shik Chi Edman
Tsang
Open Access
Abstract: Developing earth-abundant electrocatalysts that rival the commercial platinum/carbon catalyst for the hydrogen evolution reaction (HER) remains a central challenge in renewable-energy conversion. Here, we reveal an electrochemically induced, in situ phase transformation in a Ru-MgO catalyst that leads to true active material during operation. Under acidic HER conditions, nominal 20 wt.% Ru nanoparticles supported on polar MgO(111) nanocrystals undergo a topotactic hydrolysis to Ru-Mg(OH)2(001), generating an ordered hydroxide layer that serves as a highly conductive proton-hopping network. After activation, the catalyst delivers performance comparable to commercial Pt/C under identical conditions, matching the current density of −1.1 V and surpassing it by approximately 10% at −2.3 V. Operando synchrotron X-ray diffraction combined with ex situ characterization techniques directly captures this transformation, while density-functional theory calculations reveal that water-assisted Grotthuss proton transfer across the hydroxide requires only a 0.10 eV energy barrier. These findings establish electrochemically driven oxide-to-hydroxide conversion as a new design principle for creating low-Pt or Pt-free HER electrocatalysts with intrinsically fast proton transport.
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Apr 2026
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Dongpei
Ye
,
Mingyu
Luo
,
Xiaowei
Liu
,
Christopher
Foo
,
Mengqi
Duan
,
Xuelei
Pan
,
Jiasi
Li
,
Simson
Wu
,
Wei
Liu
,
Michail
Stamatakis
,
Yiyang
Li
,
Shik Chi Edman
Tsang
Open Access
Abstract: The catalytic decomposition of ammonia under mild conditions is a promising route for green hydrogen production. However, conventional dissociative ammonia decomposition pathways over metal sites are suffering from the Brønsted−Evans−Polanyi (BEP) constraint which establishes an inverse correlation between atomic N binding energy and the N-H bond dissociation energy. Herein, we report a ruthenium-supported nitrogen-doped cerium oxide (Ru/N-CeO2) catalyst that breaks this limitation and exhibits significantly enhanced catalytic activity compared to its undoped counterpart. Furthermore, we reveal that N dopants can act as independent active sites, enabling an associative mechanism distinct from the conventional Ru-driven pathway. Comprehensive isotopic labelling experiments together with computational techniques elucidate the reaction mechanism over the N site and reveal a distinct correlation between the location of the active site and catalytic activity. The proximal N site exhibits the highest activity, challenging the conventional view that activity is dominated by metal–support interfacial sites. While N doping is a commonly used approach for surface modification, our findings show that it can also alter the reaction mechanism by introducing new active sites. These insights offer valuable guidance for the rational design of catalytic supports in ammonia decomposition and open new directions for catalytic systems limited by scaling relationships in heterogenous catalysis.
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Mar 2026
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Haozhe
Zhang
,
Mengqi
Duan
,
Shuai
Guo
,
Renzo
Leeflang
,
Dorottya
Szalay
,
Jiasi
Li
,
Jo-Chi
Tseng
,
Simson
Wu
,
Songhua
Cai
,
Dharmalingam
Prabhakaran
,
Robert A.
Taylor
,
Yiyang
Li
,
Shik Chi Edman
Tsang
Open Access
Abstract: Photocatalytic ammonia decomposition offers a sustainable route for hydrogen production, but its development is limited by low catalytic efficiency and poorly understood mechanisms. Here, a protonated layered perovskite, HPrNb2O7 (HPNO), is reported as an efficient catalyst for ammonia decomposition under mild photo-thermal conditions. Upon exposure to NH3 at elevated temperatures, HPNO promotes the in situ formation and intercalation of hydrazine intermediates within its interlayer galleries, enabled by thermally generated oxygen vacancies and hydrogen bonding. Advanced characterization techniques have been applied to confirm the formation and stabilization of hydrazine. It is also shown that thermal energy prolongs charge carrier lifetimes and enhances oxygen vacancy formation, contributing to a strong photo-thermal synergy. The stabilization of hydrazine intermediate promotes the associative mechanism, lowering the activation barrier, thus leading to an enhanced hydrogen evolution rate of 1311.2 µmol·g−1·h−1 at 200 °C under simulated solar irradiation without any noble metal co-catalyst. This work reveals a distinct, hydrazine-mediated reaction pathway and positions layered protonated perovskites as promising materials for efficient, solar-driven ammonia decomposition and sustainable hydrogen generation.
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Aug 2025
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
B18-Core EXAFS
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Huihuang
Fang
,
Simson
Wu
,
Tugce
Ayvali
,
Jianwei
Zheng
,
Joshua
Fellowes
,
Ping-Luen
Ho
,
Kwan Chee
Leung
,
Alexander
Large
,
Georg
Held
,
Ryuichi
Kato
,
Kazu
Suenaga
,
Yves Ira A.
Reyes
,
Ho Viet
Thang
,
Hsin-Yi Tiffany
Chen
,
Shik Chi Edman
Tsang
Open Access
Abstract: Ammonia is regarded as an energy vector for hydrogen storage, transport and utilization, which links to usage of renewable energies. However, efficient catalysts for ammonia decomposition and their underlying mechanism yet remain obscure. Here we report that atomically-dispersed Ru atoms on MgO support on its polar (111) facets {denoted as MgO(111)} show the highest rate of ammonia decomposition, as far as we are aware, than all catalysts reported in literature due to the strong metal-support interaction and efficient surface coupling reaction. We have carefully investigated the loading effect of Ru from atomic form to cluster/nanoparticle on MgO(111). Progressive increase of surface Ru concentration, correlated with increase in specific activity per metal site, clearly indicates synergistic metal sites in close proximity, akin to those bimetallic N2 complexes in solution are required for the stepwise dehydrogenation of ammonia to N2/H2, as also supported by DFT modelling. Whereas, beyond surface doping, the specific activity drops substantially upon the formation of Ru cluster/nanoparticle, which challenges the classical view of allegorically higher activity of coordinated Ru atoms in cluster form (B5 sites) than isolated sites.
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Feb 2023
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
I11-High Resolution Powder Diffraction
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Abstract: Barium zirconate perovskites have been systematically investigated as protonic supports for ruthenium nanoparticles in the Haber–Bosch ammonia synthesis reaction. A series of supports based on barium zirconate were synthesized, for which the B-site of the ABO3 perovskite was doped with different aliovalent acceptor cations and in varying ratios, resulting in varying proton conductivities and trapping behaviors. Crucially, we provide direct evidence of the importance of a hydrogen-migration mechanism for ammonia synthesis over these proton-conducting materials from the studies of reaction kinetics, in situ X-ray photoelectron spectroscopy, and neutron powder diffraction (NPD), which requires the proper balance of oxygen vacancy concentration (B-site doping), trapping-site concentration, and proton-hopping activation energy. We report evidence of a large dynamic coverage of OH groups on the support and the first visualization of both weak and strong proton trap sites within the perovskite lattice through the use of NPD.
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Oct 2021
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
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Simson
Wu
,
Kai-Yu
Tseng
,
Ryuichi
Kato
,
Tai-Sing
Wu
,
Alexander
Large
,
Yung-Kang
Peng
,
Weikai
Xiang
,
Huihuang
Fang
,
Jiaying
Mo
,
Ian
Wilkinson
,
Yun-Liang
Soo
,
Georg
Held
,
Kazu
Suenaga
,
Tong
Li
,
Hsin-Yi Tiffany
Chen
,
Shik Chi Edman
Tsang
Abstract: Hydrogen spillover is the phenomenon where a hydrogen atom, generated from the dissociative chemisorption of dihydrogen on the surface of a metal species, migrates from the metal to the catalytic support. This phenomenon is regarded as a promising avenue for hydrogen storage, yet the atomic mechanism for how the hydrogen atom can be transferred to the support has remained controversial for decades. As a result, the development of catalytic support for such a purpose is only limited to typical reducible oxide materials. Herein, by using a combination of in situ spectroscopic and imaging technique, we are able to visualize and observe the atomic pathway for which hydrogen travels via a frustrated Lewis pair that has been constructed on a nonreducible metal oxide. The interchangeable status between the hydrogen, proton, and hydride is carefully characterized and demonstrated. It is envisaged that this study has opened up new design criteria for hydrogen storage material.
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May 2021
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I15-1-X-ray Pair Distribution Function (XPDF)
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Jianwei
Zheng
,
Lilin
Lu
,
Konstantin
Lebedev
,
Simson
Wu
,
Pu
Zhao
,
Ian J.
Mcpherson
,
Tai-Sing
Wu
,
Ryuichi
Kato
,
Yiyang
Li
,
Ping-Luen
Ho
,
Guangchao
Li
,
Linlu
Bai
,
Jianhui
Sun
,
Dharmalingam
Prabhakaran
,
Robert A.
Taylor
,
Yun-Liang
Soo
,
Kazu
Suenaga
,
Shik Chi Edman
Tsang
Abstract: Current industrial production of ammonia from the Haber-Bosch process and its transport concomitantly produces a large quantity of CO2. Herein, we successfully synthesize inorganic-structure-based catalysts with [Fe-S2-Mo] motifs with a connecting structure similar to that of FeMoco (a cofactor of nitrogenase) by placing iron atoms on a single molecular layer of MoS2 at various loadings. This type of new catalytic material functionally mimics the nitrogenase to convert N2 to ammonia and hydrogen in water without adding any sacrificial agent under visible-light illumination. Using the elevated temperature boosts the ammonia yield and the energy efficiency by one order of magnitude. The solar-to-NH3 energy-conversion efficiency can be up to 0.24% at 270°C, which is the highest efficiency among all reported photocatalytic systems. This method of ammonia production and the photocatalytic materials may open up an exciting possibility for the decentralization of ammonia production for fertilizer provision to local farmlands using solar illumination.
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Apr 2021
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B18-Core EXAFS
I11-High Resolution Powder Diffraction
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Pu
Zhao
,
Lin
Ye
,
Guangchao
Li
,
Chen
Huang
,
Simson
Wu
,
Ping-Luen
Ho
,
Haokun
Wang
,
Tatchamapan
Yoskamtorn
,
Denis
Sheptyakov
,
Giannantonio
Cibin
,
Angus I.
Kirkland
,
Chiu C.
Tang
,
Anmin
Zheng
,
Wenjuan
Xue
,
Donghai
Mei
,
Kongkiat
Suriye
,
Shik Chi Edman
Tsang
Abstract: Synthesizing atomically dispersed synergistic active pairs is crucial yet challenging in developing highly active heterogeneous catalysts for various industrially important reactions. Here, a single molecular Re species is immobilized on the inner surface of a Y zeolite with Brønsted acid sites (BASs) within atomic proximity to form Re OMS–BAS active pairs for the efficient catalysis of olefin metathesis reactions (OMS: olefin metathesis site). The synergy within the active pairs is revealed by studying the coadsorption geometry of the olefin substrates over the active pairs by synchrotron X-ray and neutron powder diffraction. It is shown that the BAS not only facilitates olefin adsorption but also aligns the olefin molecule to the Re OMS for efficient intermediate formation. Consequently, for the cross-metathesis of ethene and trans-2-butene to propene, this catalyst shows high activity under mild reaction conditions without observable deactivation. The catalyst outperforms not only traditional ReOx-based catalysts but also the best industrially applicable WOx-based catalyst thus far that we discovered previously. The concept of using two isolated active sites of different functionalities within atomic proximity in a confined cavity can provide opportunities for designing synergistically catalytic materials.
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Mar 2021
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B18-Core EXAFS
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Diamond Proposal Number(s):
[20856]
Open Access
Abstract: The catalytic synthesis of NH3 from the thermodynamically challenging N2 reduction reaction under mild conditions is currently a significant problem for scientists. Accordingly, herein, we report the development of a nitrogenase-inspired inorganic-based chalcogenide system for the efficient electrochemical conversion of N2 to NH3, which is comprised of the basic structure of [Fe–S2–Mo]. This material showed high activity of 8.7 mgNH3 mgFe−1 h−1 (24 μgNH3 cm−2 h−1) with an excellent faradaic efficiency of 27% for the conversion of N2 to NH3 in aqueous medium. It was demonstrated that the Fe1 single atom on [Fe–S2–Mo] under the optimal negative potential favors the reduction of N2 to NH3 over the competitive proton reduction to H2. Operando X-ray absorption and simulations combined with theoretical DFT calculations provided the first and important insights on the particular electron-mediating and catalytic roles of the [Fe–S2–Mo] motifs and Fe1, respectively, on this two-dimensional (2D) molecular layer slab.
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Jan 2021
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