B18-Core EXAFS
|
Diamond Proposal Number(s):
[36104]
Abstract: Seawater splitting has been considered an environmentally friendly and cost-effective method for hydrogen production. However, developing efficient electrocatalysts capable of enduring the severe corrosive conditions of natural seawaters for extended durations remains a notable technical challenge. Herein, the Ni3S2 supported NiFe oxalate ((NiFe)C2O4/Ni3S2) nanorod arrays were synthesised through hydrothermal and impregnation precipitation methods. Structural and spectroscopic analyses revealed that the (NiFe)C2O4/Ni3S2 catalyst formed an integrated oxide-sulfide interface with coexisting Ni–O/Ni–S coordination. This dual coordination environment, coupled with the presence of Fe in a higher oxidation state, confirmed interfacial electronic reorganization characterized by directional electron transfer from Ni to Fe. The resulting charge transfer pathway enhanced the electron delocalisation between active centers, thereby improving active site utilization. The obtained (NiFe)C2O4/Ni3S2 demonstrated remarkable catalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in a simulated alkaline seawater solution (NaCl + KOH), with overpotentials of 363 mV (HER) and 295 mV (OER) at a current density of 500 mA cm−2 for industrial electrolysis requirements and remarkable stability over 100 h of durability testing. Additionally, the (NiFe)C2O4/Ni3S2 electrode pairs only required a cell voltage of 1.81 V to achieve 100 mA cm−2 with Faradaic efficiency of 98 % in 1.0 M KOH + seawater. This study presents a novel approach for fabricating multifunctional electrocatalysts, providing a promising pathway for advancing seawater electrolysis and supporting the development of cost-effective green hydrogen production technologies.
|
Nov 2025
|
|
B18-Core EXAFS
|
Diamond Proposal Number(s):
[40577]
Open Access
Abstract: Mitigating climate change is one of the biggest challenges of today's society. The most direct way to achieve this goal is to capture and use CO2 as a source of energy and chemicals. This work, inspired by previous publications focused on homogeneous catalysis, proposes the transformation of the easy-to-prepare CO2 derivatives dialkylureas into C1 chemicals using Ru-MOFs as heterogeneous catalysts. This choice is due to (i) the well-known ability of Ru to catalyze hydrogenation reactions and (ii) that Ru-complexes were the pioneer homogenous catalyst in converting CO2 into an added-value C1 chemical, methanol. Apart from the already reported MOF Ru-HKUST-1, we have prepared a new Ru-MOF material, denoted Ru-BTC, analogous to the semiamorphous Fe-BTC. It has been found by XAS that Ru-BTC and Ru-HKUST-1 have different metal environment and oxidation states: only 3+ in Ru-BTC, a 50:50 mixture of 2+ and 3+ in Ru-HKUST-1. Both Ru-MOFs catalyzed the hydrogenation of N,N’-dimethylurea under relatively mild conditions, giving methane as the main product. Ru-BTC was particularly efficient: 67 % conversion and 96 % selectivity to CH4 at 150 ºC and 30 bars of H2 using a Ru/dimethylurea weight ratio of 1 %. Ru-MOFs were also able to transform CO2 into CH4, again being Ru-BTC the most effective catalyst, but giving much poorer selectivity to CH4. Ru-MOFs, particularly Ru-BTC, were damaged under reaction conditions, but no significant Ru leaching was observed.
|
Jul 2025
|
|
I18-Microfocus Spectroscopy
|
Xutong
Wang
,
Huwei
Li
,
Junxia
Wang
,
Wolfram
Buss
,
Anna
Bogush
,
Ondrej
Masek
,
Youjun
Zhang
,
Fan
Yu
,
Beibei
Yan
,
Zhanjun
Cheng
,
Xiaoqiang
Cui
,
Guanyi
Chen
,
Konstantin
Ignatyev
Diamond Proposal Number(s):
[32515]
Abstract: Recycling of sewage sludge and the endogenous phosphorus (P) is a promising strategy for sustainable development, while the disposal of heavy metals (HMs) in sewage sludge and the recovery of targeted P species remain challenges. An innovative method coupling electrokinetic treatment with pyrolysis was proposed in the present study to achieve the effective reclamation of available P and the separation of HMs from sewage sludge. The pristine and FeCl3-assisted electrokinetic treatment were employed for the removal of HMs from sewage sludge and to modify the P species, and the subsequent pyrolysis (300–700 °C) was conducted for the recovery of available P along with the production of biochar. The X-ray absorption near-edge spectroscopy (XANES), 31P liquid nuclear magnetic resonance (NMR) spectroscopy, and sequential chemical extraction were used to systematically determine the evolution of P during the combined treatment of sewage sludge. 19.69–24.80 % of Ni, Cu, and Zn were removed from sewage sludge after pristine electrokinetic treatment, and the HM removal efficiency was further elevated to 47.01–56.86 % with the assistance of FeCl3. Consequently, in comparison with the raw sewage sludge-derived biochars (SBs), the biochars derived from FeCl3-assisted electrokinetic treated sewage sludge (FESBs) contained much lower HM contents and showed higher stability of HMs. The FeCl3-assisted electrokinetic treatment converted alkaline biochars dominated by poorly soluble Ca-phosphates into neutral to slightly acidic biochars dominated by Al/Fe-associated phosphates. This transformation greatly improved the available P concentrations determined by diffusive gradients in thin film in FESBs by 0.6–1.3 folds compared to untreated SBs. Therefore, coupling FeCl3–assisted electrokinetic treatment with pyrolysis could be a promising strategy to achieve the reclamation of available P and the separation of HMs from sewage sludge.
|
Jul 2025
|
|
I20-Scanning-X-ray spectroscopy (XAS/XES)
|
Ramesh
Rijal
,
Jack
Stephens
,
Daniel
Sier
,
Nicholas T. T.
Tran
,
Truong V. B.
Nguyen
,
Jonathan W.
Dean
,
Pierce
Bowman
,
Minh
Dao
,
Paul
Di Pasquale
,
Tony
Kirk
,
Chanh Q.
Tran
,
Shusaku
Hayama
,
Matteo
Aramini
,
Nitya
Ramanan
,
Sofia
Diaz-Moreno
,
Christopher T.
Chantler
Open Access
Abstract: This study of manganese (Mn, Z = 25) introduces a novel combination of extended-range high energy resolution fluorescence detection (XR-HERFD), multiple-crystal spectrometers and advanced binary data splicing techniques to address challenges in X-ray emission spectroscopy. XR-HERFD enhances spectral precision by utilizing high-resolution crystal analysers and optimized detector configurations. The systematic application of these methods using multiple Bragg crystal analysers at Diamond Light Source has led to substantial improvements in data quality. Simultaneously, advanced binary data splicing integrates multiple datasets to correct distortions and improve resolution, resulting in sharper spectral features. Our results show a significant increase in peak counts and a notable reduction in full width at half-maximum (FWHM), with peak amplitudes increasing by 83% and resolution improving by 46%. These developments provide greater detail for X-ray absorption or emission spectra, offering valuable insights into complex materials, and permitting advances and breakthroughs in atomic relativistic quantum mechanics, chemical sensitivity of atomic transitions and modelling of solid-state effects.
|
Jul 2025
|
|
I05-ARPES
|
Zhisheng
Zhao
,
Tongrui
Li
,
Peng
Li
,
Xueliang
Wu
,
Jianghao
Yao
,
Ziyuan
Chen
,
Yajun
Yan
,
Shengtao
Cui
,
Zhe
Sun
,
Yichen
Yang
,
Zhicheng
Jiang
,
Zhengtai
Liu
,
Alex
Louat
,
Timur
Kim
,
Cephise
Cacho
,
Aifeng
Wang
,
Yilin
Wang
,
Dawei
Shen
,
Juan
Jiang
,
Donglai
Feng
Diamond Proposal Number(s):
[32274]
Abstract: The kagome metal FeGe provides a rich platform for understanding the mechanisms behind competing orders, as it exhibits charge order (CO) emerging deep within the antiferromagnetic phase. To investigate the intrinsic origin of this behavior, we examine the evolution of the low-energy electronic structure across the phase transition in annealed FeGe samples using angle-resolved photoemission spectroscopy. We find no evidence supporting a conventional nesting mechanism, such as Fermi surface nesting or van Hove singularities. However, we observe two notable changes in the band structure: an electron-like band around the K point and another around the A point, both shifting upward in energy when CO forms. These findings are consistent with our density-functional theory calculations, which suggest that the charge order in FeGe is primarily driven by magnetic energy savings due to a lattice distortion involving Ge1-dimerization. Our results provide photoemission evidence supporting this novel mechanism for CO formation in FeGe, in contrast to the conventional nesting-driven mechanisms.
|
Jun 2025
|
|
I18-Microfocus Spectroscopy
|
Diamond Proposal Number(s):
[33166]
Open Access
Abstract: Operating lithium ion batteries (LIBs) to high charging cut off potentials allows us to accommodate a further push in energy density. However, it requires a thorough understanding of the interplay and temperature dependence of parasitic reactions that aggravate the aging of the electrolyte and the cathode/anode electrodes. In the present study we investigated the interplay of the chemical and the electrochemical electrolyte oxidation, how they are related to the dissolution of transition metal (TM) ions from the cathode active material (CAM), and how they shift or accelerate with temperature. Through an optimized electrochemical protocol an excellent potential dependence of the gas evolution of a LiNi0.80Co0.15Al0.05O2 (NCA) charged against a free standing graphite on a lithium metal electrode in a LP47 electrolyte was achieved. We identified O2 and PF5 gas as suitable proxies for the chemical and electrochemical electrolyte oxidation, respectively. Both processes are separated by at least 300 mV over a temperature range from 10 to 45°C. Through temperature-dependent operando hard X ray absorption spectroscopy measurements and their comparison with the gassing results, it will be shown, that the electrochemical oxidation of the electrolyte is directly linked to the dissolution of TMs, while the chemical electrolyte oxidation mainly leaves the transition metal dissolution unaffected.
|
Jun 2025
|
|
I20-Scanning-X-ray spectroscopy (XAS/XES)
|
Diamond Proposal Number(s):
[23496]
Open Access
Abstract: Arsenic immobilization in soils and sediments is primarily controlled by its sorption onto or incorporation into reactive soil minerals, such as iron (oxyhydr)oxides. However, coexisting ions (e.g., dissolved bicarbonate, phosphate, silica, and organic matter) can negatively impact the interaction of the toxic arsenate species with iron (oxy)hydroxides. Of special note is inorganic phosphate, which is a strong competitor for sorption sites due to its analogous chemical and structural nature to inorganic arsenate. Much of our understanding of this competing nature between phosphate and arsenate focuses on the impact on mineral sorption capacities and kinetics. However, we know very little about how coexisting phosphate will alter the stability and transformation pathways of arsenate-bearing Fe (oxyhydr)oxides. In particular, the long-term fate and behavior regarding arsenate immobilization are unknown under anoxic conditions. Here, we document, through mineral transformation reactions, the immobilization of both phosphate (P) and arsenate [As(V)] in secondary mineral products and characterize their changing compositions during the transformations. We did this while controlling the initial P/As(V) ratios. Our results document that, in the absence or at low P/As(V) ratios, the initial ferrihydrite rapidly transforms to green rust sulfate (GRSO4), which further transforms into magnetite after 180 days. Meanwhile, high P/As(V) ratios resulted in a mixture of GRSO4 and vivianite, with magnetite as a minor fraction. Invariably, the speciation and partitioning of As(V) were also affected by the P/As(V) ratio. A higher P/As(V) ratio also led to a faster partial reduction of mineral-bound As(V) to As(III). The most important finding is that the initial ferrihydrite-bound As(V) became structurally incorporated into magnetite [low P/As(V) ratio] or vivianite [high P/As(V) ratio] and was thus immobilized and not labile. Overall, our results highlight the influence of coexisting phosphate in controlling the toxicity and mobility in anoxic, Fe2+-rich subsurface settings, such as contaminated aquifers.
|
Jun 2025
|
|
B18-Core EXAFS
E02-JEM ARM 300CF
|
Abstract: Catalytic hydrogenation reactions represent one of the most important transformations in the chemical industry. In the light of the required defossilization of the chemical value chain, the development of new, highly selective hydrogenation catalysts is of utmost importance to deal with renewable resources, such as biomass, recycled feedstock, or CO2. In that regard, this thesis deals with the preparation, characterization and application of metal nanoparticles (NPs) on molecularly modified surfaces for thermo- and electrocatalytic hydrogenation reactions. In the thermocatalytic systems, Mn-based NPs are investigated (monometallic and bimetallic MnRu NPs), as this earth-abundant metal possesses a low environmental impact and generally low toxicity. In addition, the electrocatalytic hydrogenation of alkenes, aldehydes and ketones using a Pickering emulsion-based system is described. Here, Pd NPs on molecularly modified carbon nanotubes are evaluated as catalyst. Firstly, small (1-10 nm) Mn NPs are immobilized on different carbon-based supports, as well as on a supported ionic liquid phase (SILP). Different synthetic methods are developed in order to optimize the properties of the NPs on each respective support, which are investigated using various characterization methods. The materials are evaluated for different catalytic transformations, with the catalytic transfer hydrogenation of aldehydes and ketones using Mn@SILP being found to be best performing. This material is demonstrated to be more active than previously reported Mn NP-based systems. X-ray absorption studies showed that the catalytic activity is highly dependent on the oxidation state of Mn. Followingly, bimetallic MnRu@SILP materials are prepared and characterized. Tuning the metal ratio of Mn:Ru enables the selective targeting of different products for substrates containing multiple reducible moieties. Furthermore, the alloying state of these NPs is investigated in order to assess its importance for the performance of the catalysts. The last part of this thesis deals with electrocatalytic hydrogenation (ECH) reactions, which offer an attractive way for the use of renewable electricity for chemical transformations. As water is used as solvent and hydrogen donor, the application of this reaction type for the conversion of apolar, organic systems is rather limited. In order to overcome this challenge, a Pickering emulsion-based system is developed. Herein, the apolar substrates are located within oil droplets, which are surrounded by an aqueous phase, providing the protons and high conductivity. This emulsion is stabilized by Pd NPs on molecularly modified CNTs. These CNTs additionally conduct electricity to the interface where the reaction is catalyzed by the Pd NPs. The mechanism of the ECH of alkenes is investigated and the reaction rate and Faradaic efficiency surpassed state-of-the-art Pd membrane reactors. The ECH system is further extended to the ECH of aldehydes and ketones to the respective alcohols. Here, the subsequent deoxygenation products can be also be yielded, which was not demonstrated yet in the electrocatalytic application of Pd NPs. Overall, this work contributes towards the development of novel catalytic systems for selective hydrogenation reactions. It can be demonstrated that metal NPs on molecularly modified surfaces represent a class of highly tunable catalysts. Their NP composition, choice of support and molecular modifier are varied to design highly efficient and selective catalysts for thermo- and electrocatalytic hydrogenation reactions.
|
Jun 2025
|
|
I09-Surface and Interface Structural Analysis
|
Bhavya
Rakheja
,
Adam
Hultqvist
,
Rahul Mahavir
Varma
,
Natalia M.
Martin
,
Karen
Radetzky
,
Stefania
Riva
,
Evelyn
Johannesson
,
Ute B.
Cappel
,
Hakan
Rensmo
,
Erik M. J.
Johansson
,
Tobias
Torndahl
Diamond Proposal Number(s):
[35209]
Open Access
Abstract: Tin oxide (SnOx) by atomic-layer deposition (ALD), in combination with fullerene, is widely employed as an electron transport layer in p–i–n perovskite solar cells. This study investigates the direct deposition of ALD SnOx on top of formamidinium (FA)-based perovskites, as a step toward the elimination of the fullerene interlayer and its poor effect on solar cell’s long-term stability. The interfacial chemistry between FA-based perovskites (FAPbI3 and FAPbBr3) and ALD SnOx was studied using soft and hard X-ray photoelectron spectroscopy (SOXPES and HAXPES) with a focus on investigating the separate roles FA and different halides play during interface formation. FAPbI3 and FAPbBr3 solar cell structures solely containing ALD SnOx resulted in s-shaped current–voltage characteristics, indicating the formation of a transport barrier at the interface. Both SOXPES and HAXPES measurements revealed the emergence of additional nitrogen states at the interface during the ALD SnOx deposition on FAPbI3 and FAPbBr3, where these states are linked to the decomposition of FA+. The FAPbI3/ALD SnOx interface also showed the presence of lead iodide (PbI2) through additional lead states other than that from FAPbI3 by using SOXPES measurements. Concerning the FAPbBr3/ALD SnOx interface, no additional lead states were observed; however, measurements instead revealed the formation of Sn–Br bonds at the interface along with the migration of bromine ions into the bulk of the ALD SnOx. Thus, FAPbI3 and FAPbBr3 undergo distinct reaction pathways upon direct deposition of ALD SnOx on top of them. We reason that the decomposition of FA+ in both perovskites and the formation of PbI2 at the FAPbI3/ALD SnOx interface and the incorporation of Br in SnOx at the FAPbBr3/ALD SnOx interface prove detrimental toward device performance. Therefore, careful interfacial engineering that can mitigate the formation of these products should be utilized to enhance the performance of perovskite solar cells.
|
Jun 2025
|
|
B18-Core EXAFS
|
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.
|
Jun 2025
|
|