B18-Core EXAFS
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Suman
Pradhan
,
Jun
Hu
,
Peng
Ren
,
Yuman
Qin
,
Noopur
Jain
,
Susanna
Monti
,
Giovanni
Barcaro
,
Aleksander
Jaworski
,
Xingchao
Dai
,
Jabor
Rabeah
,
Joaquin
Silvestre-Albero
,
Veronica
Celorrio
,
Anna
Rokicińska
,
Piotr
Kuśtrowski
,
Sandra
Van Aert
,
Sara
Bals
,
Shoubhik
Das
Diamond Proposal Number(s):
[32609]
Abstract: Regioselective C–H bond functionalization is pivotal in modern scientific exploration, offering solutions for achieving novel synthetic methodologies and pharmaceutical development. In this aspect, achieving exceptional regioselective functionalization, like para-selective products in electron-poor aromatics, diverges from traditional methods. Leveraging the advantages of atomically dispersed photocatalysts, we designed a robust photocatalyst for an unconventional regioselective aromatic C–H bond functionalization. This innovation enabled para-selective trifluoromethylations of electron-deficient meta-directing aromatics (-NO2, -CF3, -CN, etc.), which is entirely orthogonal to the traditional approaches. Mechanistic experiments and DFT analysis confirmed the interaction between Cu-atom and the aromatic substrate, alongside the photocatalyst's molecular arrangement, driving selective exposure of the para-selective functionalization. This strategic approach elucidated pathways for precise molecular transformations, advancing the frontier of regioselective C–H bond functionalization by using atomically dispersed photocatalysts in organic synthesis.
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Jun 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[40853]
Open Access
Abstract: Light-powered strategies for the semi-hydrogenation of acetylene to ethylene are rapidly emerging as sustainable alternatives to the traditional thermochemical processes. The development of a robust, selective, as well as recyclable, non-noble catalyst that can be powered by visible light and uses water as proton source to accomplish this important reaction remains a key challenge. Here the first demonstration of a cobalt single-atom catalyst supported on carbon-nitride (Co−CN) as an all-in-one photocatalyst for the semi-hydrogenation of acetylene to ethylene is reported using water as the proton source, offering advantages over current hydrogenation technologies. Carbon nitride hosts the individual catalytic active sites of cobalt thus combining photosensitizer and cocatalyst in one unit, in line with first-principles modelling. Under visible light irradiation, Co−CN reduces acetylene to ethylene with stable activity for over 40 days of continuous operation, ≥99.9% selectivity, and provides means for coupling organic upgrading to produce valuable oxidation products. The heterogeneous Co−CN can be easily recovered and reused repeatedly without loss of catalytic activity and structural integrity. Thereby, the integrated and recyclable platform overcomes the need of coupling a separate photosensitizer to a catalyst, and using noble metal catalysts with an external H2 gas feed.
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May 2025
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B18-Core EXAFS
I09-Surface and Interface Structural Analysis
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Muhammad
Ans
,
Gaurav C.
Pandey
,
Innes
Mcclelland
,
Naresh
Gollapally
,
Harry
Gillions
,
Beth I. J.
Johnston
,
Matthew J. W.
Ogley
,
James A.
Gott
,
Eleni
Fiamegkou
,
Veronica
Celorrio
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Serena A.
Cussen
,
Ashok S.
Menon
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[30104, 33553]
Open Access
Abstract: Single-crystalline LiNiO2 (SC-LNO), a high-energy-density Li-ion cathode material, suffers from poor long-term electrochemical performance when cycled above 4.2 V (vs Li+/Li). In this study, this degradation is evaluated using SC-LNO–graphite pouch cells electrochemically aged within a stressful voltage window (2.5–4.4 V) using a constant-current constant-voltage (CC-CV) protocol. Notable capacity fade is observed after one hundred cycles at C/3 rate, in addition to an increase in the overall electrochemical cell impedance. Operando X-ray diffraction data reveal that, despite no significant long-range bulk structural changes, (de-)lithiation of the aged SC-LNO becomes kinetically hindered after 100 cycles. Aging-induced changes in the short-range structure and charge compensation are evaluated through a multi-model quantitative analysis of the operando X-ray absorption spectroscopy data. While the electrochemical aging does not result in particle cracking, soft X-ray absorption spectroscopy data revealed the reconstruction of the cathode surface to a dense rock salt-like layer after long-term cycling, which acts as a kinetic trap for Li+ diffusion. Therefore, even under stressful conditions, it is the surface reconstruction that dominates the overall cathode degradation by reducing the Li+ mobility and leading to the capacity fade. Cathode surface engineering will therefore be key to improving the long-term electrochemical performance of SC-LNO cathodes.
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May 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[28356, 40853]
Abstract: The electrochemical CO2 reduction reaction (CO2RR) is a promising strategy to convert the greenhouse gas CO2 into valuable products using electricity as a feedstock. This study presents the development of single-atom copper catalyst anchored on a nitrogen and phosphorus co-doped carbon matrix designed for CO2RR. The impact of carbonization temperature on the structural properties of the electrocatalysts, such as porosity and the electronic environment, was systematically examined, revealing its influence on the selectivity towards C1 and C2+ products. Increased microporosity was associated with an enhanced hydrogen evolution reaction (HER), whereas mesoporosity contributed to improved CO2 reduction reaction activity. Aberration-corrected transmission electron microscope evidenced that P addition improved the dispersion of Cu, whether in the form of single atoms or clusters. Moreover, phosphorus doping suppressed HER and promoted the formation of products such as methane, ethylene, and ethanol. The coexistence of Cu+, Cu0, and copper single atoms was identified as key to facilitating C-C bond formation. This study emphasizes the critical balance between textural and electronic properties in optimizing catalytic performance and provides valuable insights for designing advanced electrocatalysts for CO2 valorization.
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Mar 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[28356]
Open Access
Abstract: Developing sustainable and efficient electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing energy storage technologies. This study explored the dual role of phosphorus as a dopant in carbon matrices and a key component in nickel phosphides (Ni2P and Ni12P5), synthesized using dopamine (PDA) and ammonium phosphate as eco-friendly precursors. The phase formation of nickel phosphides was found to be highly dependent on the P/PDA ratio (0.15, 0.3, 0.6, and 0.9), allowing for the selective synthesis of Ni2P or Ni12P5. Operando Raman spectroscopy revealed that both phases undergo surface transformation into nickel (oxy)hydroxide species under OER conditions, yet Ni2P-based catalysts demonstrated superior activity and long-term stability. This enhancement is attributed to efficient electron transfer at the dynamic Ni2P/NiOOH interface. Additionally, hollow nanostructures formed at intermediate P/PDA ratios (≤0.3) via the Kirkendall effect and Ostwald ripening contributed to an increased specific surface area and micropore volume, further improving the catalytic performance. Electrochemical impedance spectroscopy confirmed reduced interfacial resistance and enhanced charge transport. These findings offer new insights into the rational design of high-performance electrocatalysts and propose a green, tunable synthesis approach for advanced energy conversion applications.
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Mar 2025
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B18-Core EXAFS
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Ajay Piriya
Vijaya Kumar Saroja
,
Yupei
Han
,
Charlie A. F.
Nason
,
Gopinathan
Sankar
,
Pan
He
,
Yi
Lu
,
Henry R.
Tinker
,
Andrew
Stewart
,
Veronica
Celorrio
,
Min
Zhou
,
Jiayan
Luo
,
Yang
Xu
Diamond Proposal Number(s):
[30102]
Open Access
Abstract: MoS2 is regarded as one of the most promising potassium-ion battery (PIB) anodes. Despite the great progress to enhance its electrochemical performance, understanding of the electrochemical mechanism to store K-ions in MoS2 remains unclear. This work reports that the K storage process in MoS2 follows a complex reaction pathway involving the conversion reactions of Mo and S, showing both cationic redox activity of Mo and anionic redox activity of S. The presence of dual redox activity, characterized in-depth through synchrotron X-ray absorption, X-ray photoelectron, Raman, and UV–vis spectroscopies, reveals that the irreversible Mo oxidation during the depotassiation process directs the reaction pathway toward S oxidation, which leads to the occurrence of K–S electrochemistry in the (de)potassiation process. Moreover, the dual reaction pathway can be adjusted by controlling the discharge depth at different cycling stages of MoS2, realizing a long-term stable cycle life of MoS2 as a PIB anode.
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Oct 2024
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B18-Core EXAFS
I21-Resonant Inelastic X-ray Scattering (RIXS)
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Matthew J. W.
Ogley
,
Ashok S.
Menon
,
Gaurav C.
Pandey
,
Galo J.
Paez Fajardo
,
Beth J.
Johnston
,
Innes
Mcclelland
,
Veronika
Majherova
,
Steven
Huband
,
Debashis
Tripathy
,
Israel
Temprano
,
Stefano
Agrestini
,
Veronica
Celorrio
,
Gabriel E.
Perez
,
Samuel G.
Booth
,
Clare P.
Grey
,
Serena A.
Cussen
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[33292, 33173]
Open Access
Abstract: This study refutes the commonly used ionic-bonding model that demarcates transition metal (TM) and oxygen redox using an archetypal Ni-rich layered oxide cathode, LiNi0.8Mn0.1Co0.1O2. Here, charge compensation during delithiation occurs without formal (ionic) Ni oxidation. Instead, oxygen-dominated states control the redox process, facilitated by strong TM-O hybridization, forming bulk-stable 3d8L and 3d8L2 electronic states, where L is a ligand hole. Bulk O–O dimers are observed with O K-edge resonant inelastic X-ray scattering but, critically, without the long-range TM migration or void formation observed in Li-rich layered oxides. Above 4.34 V vs. Li+/Li, the cathode loses O, forming a resistive surface rock-salt layer that causes capacity fade. This highlights the importance of cathode engineering when attempting to achieve higher energy densities with layered oxide cathodes, especially in those where O dominates the charge compensation mechanism.
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Oct 2024
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I20-EDE-Energy Dispersive EXAFS (EDE)
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Diamond Proposal Number(s):
[28203]
Abstract: Understanding nature of intermediates/active species in reactions is a major challenge in chemistry. This is because spectator species typically dominate the experimentally derived data and consequently active phase contributions are masked. Transient methods offer a means to bypass this difficulty. In particular, modulation excitation with phase-sensitive detection (ME-PSD) provides a mechanism to distinguish between spectator and reacting species. Herein, modulation excitation (ME) time-resolved (energy dispersive) X-ray absorption spectroscopy, assisted by phase sensitive detection (PSD) analysis, has been applied to the study of a liquid phase process; in this case the classic ferrocyanide/ferricyanide redox couple. Periodic switches of the electrical potential (anodic/cathodic) enabled the use of the ME approach. Structural changes at fractions as low as 2% of the total number of electroactive species were detected within the X-ray beam probe volume containing ~30 pmol of Fe(II)/Fe(III).
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Aug 2024
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B18-Core EXAFS
I21-Resonant Inelastic X-ray Scattering (RIXS)
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Matthew
Ogley
,
Ashok S.
Menon
,
Beth J.
Johnston
,
Gaurav
Pandey
,
Innes
Mcclelland
,
Xiaoqun
Shi
,
Stefano
Agrestini
,
Veronica
Celorrio
,
Gabriel E.
Perez
,
Samuel G.
Booth
,
Jordi
Cabana
,
Serena A.
Cussen
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[33292, 33173]
Open Access
Abstract: In layered lithium transition metal oxide cathodes, high-voltage operation is accompanied by the formation of oxygen dimers, which are widely used as an indicator of oxygen-redox activity. However, understanding the role that oxygen dimerization plays in facilitating charge compensation is still needed. Li2NiO3 (a 3d8L2-containing compound, where L is a ligand hole) is studied as a model system, where oxygen dimerization is shown to occur without cathode oxidation. Electrochemical cycling results in a net reduction of the cathode, accompanied by structural transformations, despite spectroscopic features of oxygen dimers arising at the top-of-charge. Here, oxygen dimerization is shown to coexist alongside a structurally transformed and electronically reduced cathode structure, thus highlighting that O dimerization is independent of bulk redox processes. This makes it clear that a thermodynamically derived transformation toward a reduced phase remains the only variable capable of generating O–O dimers in Li2NiO3.
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Aug 2024
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B18-Core EXAFS
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Claudio
Cometto
,
Giulia
Marafon
,
Veronica
Celorrio
,
Gonzalo
Garcia
,
Steffi Y.
Woo
,
Enrico
Paron
,
Alberto
Zobelli
,
Gregorio
Bottaro
,
Lidia
Armelao
,
Elena
Pastor
,
Alessandro
Moretto
,
Laura
Calvillo
Diamond Proposal Number(s):
[19850]
Open Access
Abstract: The development of active, selective, and durable (photo)electrocatalytic hybrid systems by combining molecular catalysts and semiconductor substrates is crucial for efficiently converting solar light into high-value products. Herein, a one-step synthesis method to obtain carbon nitride (CN) nanosheets, which allows the direct covalent polymerization with molecular catalysts, was developed. Copper-porphyrin (CuPor) units were embedded in the CN structure as a case-study. The single and hybrid materials were fully characterized by combining microscopic and spectroscopic techniques and tested as (photo)electrocatalysts for the CO2 reduction reaction (CO2RR) in aqueous solution. Experimental evidence confirmed an effective boost of the CN photoelectrocatalytic activity by introducing the CuPor units. Formate was identified as the only CO2RR product on both CuPor and CuPor-CN, simultaneously with hydrogen from the competitive hydrogen evolution reaction. However, the formate/hydrogen ratio was higher when the hybrid material was used as catalyst, suggesting a synergetic effect between CuPor and CN, that favors the CO2RR and hinders the HER. In addition, the stability of the CuPor units in the CN matrix under catalytic conditions was studied by in situ X-ray absorption. No changes of the Cu porphyrin structure or formation of copper clusters/nanoparticles was observed as a function of the applied potential nor after an accelerated ageing treatment, suggesting that the CN matrix is able to stabilize the Cu sites avoiding their agglomeration.
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Aug 2024
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