Qingyu Kong

SOLEIL synchrotron · Science Division

Single‐atom and vacancy‐engineered photocatalysts have shown their remarkable strengths in improving carrier transfer dynamics, yet constructing the integration of single atoms and vacancies as the active site is still challenging. Herein, an icing‐assisted photochemical strategy has been employed to anchor Pd single atoms in Zn vacancies on Cd x Z...

Metalloporphyrins with open d-shell ions can drive biochemical energy cycles. However, their utilization in photoconversion is hampered by rapid deactivation. Mapping the relaxation pathways is essential for elaborating strategies that can favorably alter the charge dynamics through chemical design and photoexcitation conditions. Here, we combine t...

Li‐rich layered oxides (LRLO) exhibit significant potential for use in all‐solid‐state lithium batteries (ASSLBs) owing to their high capacities and wide range of operating voltages. However, the practical application of LRLO in ASSLBs is hindered by the severe failure of carrier transport at the solid–solid interface, which subsequently limits the...

Oxygen evolution reaction (OER) plays a key role in proton exchange membrane water electrolysis, yet the electrocatalysts still suffer from the disadvantages of low activity and poor stability in acidic conditions. Here, we have successfully fabricated a new class of CdRu 2 IrO x nanoframes with distorted structure for acidic OER. Impressively, CdR...

Designing an efficient catalyst for acidic oxygen evolution reaction (OER) is of critical importance in manipulating proton exchange membrane water electrolyzer (PEMWE) for hydrogen production. Here, we report a fast, nonequilibrium strategy to synthesize quinary high-entropy ruthenium iridium-based oxide (M-RuIrFeCoNiO 2 ) with abundant grain boun...

Pursuing highly active and long‐term stable ruthenium (Ru) based oxygen evolution reaction (OER) catalyst for water electrolysis under acidic conditions is of great significance yet a tremendous challenge to date. To solve the problem of serious Ru corrosion in an acid medium, the trace lattice sulfur (S) inserted RuO2 catalyst is prepared. The opt...

The research on perylene diimide (PDI) aggregates effectively promotes their applications in organic photovoltaic solar cells and fluorescent sensors. In this paper, a PDI fabricated with three peripheral PDI units (N, N’-bis(6-undecyl) perylene-3,4,9,10-bis(dicarboximide)) is investigated. The trimer shows different absorption and fluorescence pro...

Excited state intramolecular proton transfer process is of great importance in solar light conversion and white light emitting systems. The excited state intramolecular proton transfer process of 1,4-dihydroxyanthraquinone in acetonitrile was investigated by steady-state spectroscopy, transient absorption spectroscopy and density functional theory...

Ru has recently been regarded as a promising catalyst for hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) due to its similar binding energy towards *H but lower price compared to Pt. Nevertheless, the quest of high-efficiency Ru-based catalysts for HOR and HER is driven by the current disadvantages including low activity and...

Vacancies have been proved effective in activating the oxygen redox and stabilizing the structure of the oxide cathode materials for the Na-ion batteries, but their effect on the cathode materials...

Photolysis reaction pathways of [Au(III)Cl4]- in aqueous solution have been investigated by time-resolved X-ray absorption spectroscopy. Ultraviolet excitation directly breaks the Au-Cl bond in [Au(III)Cl4]- to form [Au(II)Cl3]- that becomes highly reactive within 79 ps. Disproportionation of [Au(II)Cl3]- generates [Au(I)Cl2]-, which is stable for...

Carbon nanocages (CNCs) have attracted tremendous interest in heterogeneous catalysis due to their promising properties of porous structure and improved mass transfer. Nevertheless, the controlled synthesis of CNCs remains a great challenge. Herein, we have shown the successful construction of functionalized N-doped CNCs (NCNCs) via a one-stone-two...

Chalcogenides have been viewed as important conversion‐type Mg²⁺‐storage cathodes to fulfill the high volumetric energy density promise of magnesium (Mg) batteries. However, the low initial Columbic efficiency and the rapid capacity degradation remain challenges for the chalcogenide cathodes, as the clear Mg²⁺‐storage mechanism has yet to be clarif...

The Ni-rich layer-structured oxide is one of the most promising candidate cathode materials for the high energy-density Li-ion batteries. However, the commercial applications of these materials are hindered with drawbacks such as structural instability and poor cycling performance at high potentials. Herein, we comprehensively studied the oxygen re...

Chalcogenides have been viewed as important conversion‐type Mg 2+ ‐storage cathodes to fulfill the high volumetric energy density promise of magnesium (Mg) batteries. However, the low initial Columbic efficiency and the rapid capacity degradation remain challenges for the chalcogenide cathodes, as the clear Mg 2+ ‐storage mechanism has yet to be cl...

Solid‐state zinc (Zn) batteries offer a new candidate for emerging applications sensitive to volume, safety and cost. However, current solid polymeric or ceramic electrolyte structures remain poorly conductive for the divalent Zn²⁺, especially at room temperature. Constructing a heterogeneous interface which allows Zn²⁺ percolation is a viable opti...

This is the first study on a Ru(bda) (bda: 2,2′-bipyridine-6,6′-dicarboxylic acid) catalyst in solution using a home-built electrochemical cell, in combination with an energy-dispersive X-ray absorption spectroscopy setup. The oxidation...

Solid‐state zinc (Zn) batteries offer new desirable candidate for emerging applications sensitive to volume, safety and cost. However, current solid polymeric or ceramic electrolyte structures remain poorly conductive for the divalent Zn2+, especially at room temperature. Constructing a heterogeneous interface which allows Zn2+ percolation is a via...

The layered manganese oxide cathode materials suffer from the Jahn-Teller effect of the octahedral Mn³⁺ ions at low potentials and the anionic oxidation triggered structural degradation at high potentials. Introduction of vacancies in the transition metal layer has proved effective in stabilizing the structure at both the high and low potentials. H...

This review focuses on how short X-ray pulses from synchrotrons and XFELs can be used to track light-induced structural changes in molecular complexes and proteins via the pump–probe method. The upgrade of the European Synchrotron Radiation Facility to a diffraction-limited storage ring, based on the seven-bend achromat lattice, and how it might bo...

Understanding solid-state zinc-ion conduction will not only be academically interesting but also benefit the development of energy-dense devices. However, zinc ions in conventional ceramic and polymer hosts is only mobile at high temperatures, and intriguing questions remain regarding the correlation between ionic local environment and conductivity...

Photoluminescence (PL) characterization spectrum has been widely used to study the electronic energy levels. Following the quantum transition rule, the PL is usually dominant to one strong peak. Ho3+ is one of the commonly used doping element to provide the PL with concentration limited to 1 in pyrochlore Ho2Sn2O7 through pressure treatment at room...

Layered transition metal (TM) oxides have aroused enormous interest in both fundamental and applied cathode material research in the context of high energy‐density batteries. Although various mechanisms have been proposed to explain their significant initial capacity losses, the effect of the local structural defects on performance has been largely...

Despite their intrinsic safety and cost-effectiveness, aqueous zinc (Zn)-organic batteries have been struggling with the rapid performance degradation arising from the poor reversibility of Zn anodes and the dissolution of cathodes. Here, we present a new aqueous eutectic electrolyte by coupling a hydrated Zn salt (Zn(ClO4)2·6H2O) exclusively with...

Sluggish kinetics and poor reversibility of cathode chemistry is the major challenge for magnesium batteries to achieve high volumetric capacity. Introduction of the cuprous ion (Cu⁺) as a charge carrier can decouple the magnesiation related energy storage from the cathode electrochemistry. Cu⁺ is generated from a fast equilibrium between copper se...

The right chemistry: A chemical, rather than electrochemical, magnesiation/ de‐magnesiation process with the assistance of the Cu⁺ equilibrium is revealed. It guarantees fast charging/discharging processes and long‐term durability of rechargeable Mg batteries under practically high mass‐loading conditions. Abstract Sluggish kinetics and poor rever...

There is a long-standing consciousness that the rhombohedral NASICON-type compounds as promising cathodes for Li+ /Na+ batteries should have inactive M1(6b) sites with ion (de)intercalation occurring only in the M2 (18e) sites. Of particular significance is that M1 sites active for charge/discharge are commonly considered undesirable because the io...

Lithium‐rich layered oxides are promising candidate cathode materials for the Li‐ion batteries with energy densities above 300 Wh kg⁻¹. However, issues such as the voltage hysteresis and decay hinder their commercial applications. Due to the entanglement of the transition metal (TM) migration and the anionic redox upon lithium extraction at high po...

The photochemical reaction pathways of CHBr3 in solution were unveiled using two complementary X-ray techniques, time-resolved X-ray solution scattering (TRXSS) and X-ray transient absorption spectroscopy, in a wide temporal range from 100 ps to tens of microseconds. By performing comparative measurements in protic (methanol) and aprotic (methylcyc...

The interplay between ferroelectricity and magnetism in multiferroic materials is of great scientific and technological interest, allowing magnetic control of ferroelectric properties and electric control of magnetic properties through the magnetoelectric coupling from interfacial strain, exchange bias, or charge-transfer process. We report the cha...

Using a highly stoichiometric magnetite, the pressure-induced phase transitions of Fe3O4 have been revisited here by performing Fe K-edge x-ray absorption and magnetic circular dichroism measurements up to P=65 GPa at room temperature and 71 GPa at 20 K. We have observed a structure transition at around 27 GPa from magnetite to a high pressure phas...

Vacancy-ordered lead free perovskites with more stable crystalline structure have been intensively explored as the alternatives for resolving the toxic and long-term stable issues of Lead halide perovskites (LHPs). The dispersive energy bands produced by the closely packed halide octahedral sublattice in these perovskites are meanwhile anticipated...

Using femtosecond resolution X-ray solution scattering at a free electron laser we were able to directly observe metal-metal bond cleavage upon photolysis at 400 nm of Ru3(CO)12, a prototype for the photochemistry of transition metal carbonyls. This leads to the known single intermediate Ru3(CO)11(μ-CO)*, with a bridging ligand (μCO) and where the...

Cathode materials with high energy density, long cycle life, and low cost are of top priority for energy storage systems. The Li‐rich transition metal (TM) oxides achieve high specific capacities by redox reactions of both the TM and oxygen ions. However, the poor reversible redox reaction of the anions results in severe fading of the cycling perfo...

The development of next generation high energy density lithium ion batteries (LIBs) adopting electrode materials with higher specific capacity or higher working voltage has attracted great interests. In this paper, fluoroethylene carbonate (FEC) and 1,3-propanediolcyclic sulfate (PCS) are unprecedentedly combined as hybrid functional additives to s...

One of the goals of several beamlines at the SOLEIL synchrotron is to develop new experimental set-ups to carry out time-resolved studies by using pump-probe experimental schemes. The SOLEIL detector group is testing a hybrid pixel detector responding to the specifications of this type of measurements. In order to evaluate the detector performances...

Photoinduced electronic and structural changes of a hydrogen-generating supramolecular RuPt photocatalyst are studied by a combination of time-resolved photoluminescence, optical transient absorption, and X-ray absorption spectroscopy. This work uses the element specificity of X-ray techniques to focus on the interplay between the photophysical and...

Motivated by the prediction of surface Kondo breakdown in topological Kondo insulators, we investigated the valence and magnetism of SmB6 with x-ray absorption and magnetic circular dichroism at the Sm M4,5 and L2 edges with surface and bulk sensitivity, respectively. A higher Sm valence state at the surface and in the bulk under pressure indicates...

The photochemistry of halomethanes is fascinating for the complex cascade reactions toward either the parent or newly synthesized molecules. Here, we address the structural rearrangement of photodissociated CH2IBr in methanol and cyclohexane, probed by time-resolved X-ray scattering in liquid solution. Upon selective laser cleavage of the C–I bond,...

Cobalt-carbon bond cleavage is crucial to most natural and synthetic applications of the cobalamin class of compounds and here we present the first direct electronic and geometric structural characteristics of intermediates formed following photoexcitation of methylcobalamin (MeCbl) using time-resolved X-ray absorption spectroscopy (XAS). We catch...

The abundant resource of sodium (Na) makes the Na-ion batteries a promising alternate to the Li-ion batteries in electric energy storage, especially when iron (Fe)-based oxide electrodes are used. Layer-structured NaxFeyM1-yO2 (M for Mn and Ni, etc.), for example, has drawn much attention and is one type of the most attractive cathode materials for...

Photolysis of iodoform (CHI3) in solution has been extensively studied but its reaction mechanism remains elusive. In particular, iso-iodoform (iso-CHI2–I) is formed as a product of the photolysis reaction, but its detailed structure is not known and whether it is a major intermediate species has been controversial. Here, by using time-resolved X-r...

Here we present a facile aqueous approach to synthesize heterostructure CdSe/CdS QDs with all-inorganic chalcogenides S2- ligands under mild conditions. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and steady-state emission spectroscopy demonstrate tha...

Colloidal quantum dots (QDs) have demonstrated great promise in artificial photosynthesis. However, the ultra-small size hinders its controllable and effective interaction with cocatalysts. To improve the poor interparticle electronic communication between free QD and cocatalyst, we design here a self-assembled architecture of nanoparticles, QDs an...

A novel α-CrPO4-type vanadium-based orthophosphate NaV3(PO4)3 was synthesized as a promising anode material for Na-ion batteries, which exhibits a high reversible capacity of 140 mA h g⁻¹ with the capacity retention about 98% after 100 cycles. Furthermore, the electrochemical reaction mechanism, structure evolution and ionic diffusion of NaV3(PO4)3...

Ultrafast time-resolved studies of photocatalytic thin films can provide a wealth of information crucial for understanding and thereby improving the performance of these materials by directly probing electronic structure, reaction intermediates, and charge carrier dynamics. The interpretation of transient spectra, however, can be complicated by the...

X-ray transient absorption spectroscopy (XTA) and optical transient spectroscopy (OTA) were used to probe the Co(I) intermediate generated in situ from an aqueous photocatalytic hydrogen evolution system, with [RuII(bpy)3]Cl2•6H2O as the photosensitizer, ascorbic acid/ascorbate as the electron donor, and the Co-polypyridyl complex ([CoII(DPA-Bpy)Cl...

Echoing the roaring success of their bulk counterparts, nano-objects built from organolead halide perovskites (OLHP) present bright prospects for surpassing the performances of their conventional organic and inorganic analogues in photodriven technologies. Unraveling the pho-toinduced charge dynamics is essential for optimizing the optoelectronic f...

The development of excellent performance of Na-ion batteries remains great challenge owing to the poor stability and sluggish kinetics of cathode materials. Herein, B substituted Na3V2P3 -x B x O12 (0 ≤ x ≤ 1) as stable cathode materials for Na-ion battery is presented. A combined experimental and theoretical investigations on Na3V2P3 -x B x O12...

Ni(OH)2 have emerged as important functional materials for solar fuel conversion because of their potential as cost-effective bifunctional catalysts for both hydrogen and oxygen evolution reactions. However, their roles as photocatalysts in the photoinduced charge separation (CS) reactions remain unexplored. In this paper, we investigate the CS dyn...

Layer-structured oxides are the basis subject for their essential roles in various applications (e.g. high-energy batteries and superconductors) due to their distinctive physical structures and chemical properties. Most of the layered AxMO2 (A=alkali ions, M= transition metals) are composed of MO6 octahedrons and varied A coordination polyhedron su...

CuS nanocrystals are potential materials for developing low-cost solar energy conversion devices. Understanding the underlying dynamics of photoinduced carriers in CuS nanocrystals is essential to improve their performance in these devices. In this work, we investigated the photoinduced hole dynamics in CuS nanodisks (NDs) using the combination of...

The effect of solute-solvent interaction on molecular structure and reaction dynamics has been a target of intense studies in solution-phase chemistry, but it is often challenging to characterize the subtle effect of solute-solvent interaction even for the simplest diatomic molecules. Since the I2 molecule has only one structural parameter and exhi...

The intensity of single X-ray pulses from third generation synchrotrons like the ESRF, APS and Spring8 is now so high that it is feasible to conduct time resolved experiment with diffraction, scattering and spectroscopic techniques on samples ranging from small molecules to proteins, with 100 ps time resolution. This limit is dictated by the X-ray...

Li-rich layered Li1+xMnyM1−x−yO2 (or denoted xLi2MnO3·(1 − x)LiMO2, M = Ni, Co, Mn, etc.) are promising cathode materials for high energy-density Li-ion batteries. However, their commercial applications suffer from problems such as a drop in the capacity and discharge voltage during cycling. In this work, the cycling performance of a layered oxide...

Lithium-rich layer-structured oxides xLi2MnO3·(1�x)LiMO2 (0<x<1, M=Mn, Ni, Co, etc.) are interesting and potential cathode materials for high energy-density lithium ion batteries. However, the characteristic charge compensation contributed by O2� in Li2MnO3 leads to the evolution of oxygen during the initial Li+ ion extraction at high voltage and v...

Li 2 MnO 3 stabilizes the structure of Li M O 2 ( M = Mn, Ni, Co, etc .) and makes Li-rich layer-structured x Li 2 MnO 3 ·(1- x )Li M O 2 (0< x <1.0, M = Mn, Ni, Co, etc .) composites (or solid solutions) become potential cathode materials for high energy density lithium ion batteries. However, as Mn ⁴⁺ is inactive in Li 2 MnO 3 , the charge compen...

Determining the electronic and geometric structures of photo-excited transient species with high accuracy is crucial for understanding their fundamental photochemistry and controlling their photoreactivity. We have applied X-ray transient absorption spectroscopy to measure the XANES and EXAFS spectra of a dilute (sub mM) solution of an osmium (II)...

Layer-structured xLi2MnO3·(1 − x)LiMO2 are promising cathode materials for high energy-density Li-ion batteries because they deliver high capacities due to the stabilizing effect of Li2MnO3. However, the inherent disadvantages of Li2MnO3 make these materials suffer from drawbacks such as fast energy-density decay, poor rate performance and safety h...

Polythiophene (PTh)-based coordination complexes, polythiophene iron (PTh Fe) and polythiophene iron oxygen (PTh-Fe-O) were synthesized by chemical method and proved to be novel high-performance organometallic lithium-storage materials. Extended X-ray absorption fine structural (EXAFS) spectroscopy and density functional theory (DFT) calculations i...

Graphene-like and platelike WS2 were obtained by solid-state reactions. High-resolution (HR) TEM, BET, and Raman scattering studies show that the graphene-like WS2 is a few-layer-structured material. It exhibits better electrochemical performances than the platelike WS2 . Structural characterization indicates that metallic W and Li2 S are the end p...

Molecules are often born with high energy and large-amplitude vibrations. In solution, a newly formed molecule cools down by transferring energy to the surrounding solvent molecules. The progression of the molecular and solute−solvent cage structure during this fundamental process has been elusive, and spectroscopic data generally do not provide su...

Microsecond (μs) time-resolved extended X-ray absorption fine structure spectroscopy (EXAFS) has been developed using an energy-dispersive EXAFS (EDE) setup equipped with a silicon Quantum Detector ULTRA. The feasibility was investigated with a prototypical thermally driven redox reaction, the thermal decomposition of (NH(4))(2)[PtCl(6)]. EXAFS dat...

Microsecond time-resolved energy-dispersive EXAFS measurement and its application to film the thermolysis of (NH4)2[PtCl6]

Time-resolved diffuse X-ray scattering is one powerful method for monitoring the progression from the creation of local structural changes inside a crystalline material up to the transformation of the whole crystalline bulk. In this work, we study the mechanism of phototransformation of a molecular crystal by time-resolved diffuse X-ray scattering....

The growth of gold nanorods has been followed by small angle X-ray scattering and X-ray absorption. The synthesis is performed at high concentration of 3.5 mM in gold using in situ generation of seeds. It is shown that the growth occurs at constant number density of nanoparticles after the initial nucleation of seeds and that the final step of redu...

The enormous gain in intensity from undulators has led to an equivalent gain in time resolution and some techniques can now be performed routinely at synchrotrons at a time resolution of 100 picoseconds, a limit set by the X-ray pulse length. In the simplest time-resolved experiment, the evolution of a process is recorded by the detector just as a...

Current lithium-ion battery (LIB) technologies are all based on inorganic electrode materials, though organic materials have been used as electrodes for years. Disadvantages such as limited thermal stability and low specific capacity hinder their applications. On the other hand, the transition metal oxides that provide high lithium-storage capacity...

Current lithium ion battery (LIB) technologies are all based on inorganic electrodes though organic materials have been hyped as electrodes for years. Disadvantages such as low specific capacity and poor rate performance hinder their applications. Here we report a novel high-performance organometallic lithium-storage material, a polypyrrole-iron-ox...

X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) under pressure are probes of local order and microscopic magnetic properties. XMCD is a selective probe that has access to a large variety of elements. The dispersive extended X-ray absorption fine structure (EXAFS) station at SOLEIL (ODE beam line) provides the possib...

A polymer-coated Co3O4 composite was electrochemically induced to be a high-performance lithium-storage material. The structure of the composite before and after electrochemical charge/discharge cycling was determined by extended X-ray absorption fine structure spectroscopy (EXAFS) and density functional theory (DFT) calculations. It is found that...

We investigate the photoinduced dissociation of HgBr(2) in methanol and the ensuring structural dynamics of the photo-products over a time span from 100 ps to 1 μs after photolysis at 267 nm by using time-resolved X-ray liquidography (TRXL). By making use of the atomic-level structural sensitivity of X-ray scattering and the superb 100 ps time reso...

Information about temporally varying molecular structure during chemical processes is crucial for understanding the mechanism and function of a chemical reaction. Using ultrashort optical pulses to trigger a reaction in solution and using time-resolved X-ray diffraction (scattering) to interrogate the structural changes in the molecules, time-resol...

A comprehensive study of the mechanism of gold nanoparticle formation has been conducted using third-generation synchrotrons. The particles were obained by reduction of AuCl(3) by BH(4)(-) in toluene. Gold oxidation state was monitored by X-ray absorption near edge spectroscopy (XANES), while the size and concentration of the nanoparticles were ass...

A time-resolved X-ray solution scattering study of bromine molecules in CCl(4) is presented as an example of how to track atomic motions in a simple chemical reaction. The structures of the photoproducts are tracked during the recombination process, geminate and non-geminate, from 100 ps to 10 micros after dissociation. The relaxation of hot Br(2)(...

Ultrafast (ps) time-resolved X-ray scattering was used to study the structural dynamics of Ru(3)(CO)(12) in cyclohexane after photolysis at 260 nm. Two intermediates form after 100 ps at the onset of the reaction: Ru(3)(CO)(10) for the CO loss channel and Ru(3)(CO)(11)(mu-CO) for the metal-metal cleavage channel. In our previous study at 390 nm, by...

Information about temporally varying molecular structure during chemical processes is crucial for understanding the mechanism and function of a chemical reaction. Using ultrashort optical pulses to trigger a reaction in solution and using time-resolved X-ray diffraction (scattering) to interrogate the structural changes in the molecules, time-resol...

The ultrafast structural dynamics of the [2+2] photocycloaddition of alpha-styrylpyrylium trifluoromethanesulfonate (TFMS) has been studied in great detail. During the photoreaction, optical and infrared spectroscopy confirms that crystals of alpha-styrylpyrylium change color. Since the reaction is reversible, it has been suggested to be used as an...

Information about temporally varying molecular structure during chemical processes is crucial for understanding the mechanism and function of a chemical reaction. Using ultrashort optical pulses to trigger a reaction in solution and using time-resolved X-ray diffraction (scattering) to interrogate the structural changes in the molecules, time-resol...

The structural kinetics of photo-induced elimination reaction of 1,2-diiodotetrafluoroethane in solution is examined by transient X-ray diffraction. The structure of .CF2CF2I is determined to be a classical mixture of anti and gauche forms and their decay mechanism is also tracked in real time.

Molecular movies: Time-resolved X-ray scattering provides direct structural information on an electronically excited complex while it is formed in the bimolecular reaction between excited octahydrogen[tetrakis-mu-diphosphito-1kappaP:2kappaP'-diplatinate](4-) (PtPOP*) and thallium ions. In the exciplex one thallium(I) and two platinum(II) ions are f...