Abstract
Amorphous nano-metal catalysts often exhibit appealing catalytic properties, because the intrinsic linear scaling relationship can be broken. However, accurate control synthesis of amorphous ...nano-metal catalysts with desired size and morphology is a challenge. In this work, we discover that Cu(0) could be oxidized to amorphous Cu
x
O species by supercritical CO
2
. The formation process of the amorphous Cu
x
O is elucidated with the aid of machine learning. Based on this finding, a method to prepare Cu nanoparticles with an amorphous shell is proposed by supercritical CO
2
treatment followed by electroreduction. The unique feature of this method is that the size of the particles with amorphous shell can be easily controlled because their size depends on that of the original crystal Cu nanoparticles. Moreover, the thickness of the amorphous shell can be easily controlled by CO
2
pressure and/or treatment time. The obtained amorphous Cu shell exhibits high selectivity for C2+ products with the Faradaic efficiency of 84% and current density of 320 mA cm
−2
. Especially, the FE of C2+ oxygenates can reach up to 65.3 %, which is different obviously from the crystalline Cu catalysts.
In this work, the La-metal–organic frameworks (La-MOFs) were synthesized using lanthanum(III) nitrate and 1,3,5-benzenetricarboxylic acid (BTC) in H2O-in-1-butyl-3-methylimidazolium ...hexafluorophosphate (bmimPF6), bmimPF6-in-water, and the bicontinuous microemulsions stabilized by surfactant TX-100. The MOFs prepared were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and FT-IR methods, and the microstructures of the microemulsions in the H2O/bmimPF6/TX-100 system were studied by small-angle X-ray scattering (SXAS) technique. It was shown that the dispersed droplets in the water-in-bmimPF6, bicontinuous and bmimPF6-in-water microemulsions were spherical, lamellar, and cylindrical, respectively. The shapes of the La-MOFs synthesized were similar to that of the droplets in the corresponding microemulsions. This indicated that the morphology of MOFs could be controlled by the microstructures of the microemulsions. On the basis of the systematic experimental results, the mechanism for controlling the morphology of the MOFs was proposed.
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•Crystallinity and β-phase content are enhanced by addition of water and hydrate salt.•β- and α-phase will transform into each other via the variation of the water content.•MgCl2⋅6H2O ...indicates functions including as the nucleation sites for crystallization.
In this study, the effects of solvent and magnesium chloride hexahydrate (MgCl2⋅6H2O) on the polymorphism of polyvinylidene fluoride (PVDF) thin films were systematically investigated. Wherein, N,N-dimethylformamide (DMF) and water with different volume ratio were used as mixed solvents to obtain the solution casting films, P series. In addition, MgCl2⋅6H2O was comparatively added to prepare PVDF/MgCl2⋅6H2O hybrid films, P-M series. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and differential scanning calorimeter (DSC) were utilized to study the influence of the water content in the mixed solvents and the hydrated salt on crystallization behavior of PVDF. Further, the morphologic images from scanning electronic microscopy (SEM) and polarized optical microscopy (POM), as well as the pizoelectirc d33 test also supplies the corresponding evidences. As indicated, the water in the mixed solvent shows different effect on main crystal forms of PVDF. At low water content, the solvents may favor the polar phase (β- and γ-phase) mainly by hydrogen bonds interactions between PVDF and water, together with dipolar interactions between PVDF and DMF. At high water content, the nonsolvent water will impose confinement effect on polymer chain diffusion and crystal growth which facilitate the formation of α-phase PVDF. Moreover, magnesium chloride hexahydrate mainly functioned as the nucleation sites for PVDF crystallization. The result of small-angle X-ray scattering (SAXS) implies the content of water or MgCl2⋅6H2O has little impact on the structure of the long period.
The microminiaturization of detectors used to record the intensity of X‐ray beams is very favorable for combined X‐ray experimental techniques. In this paper, chemical‐vapor‐deposited (CVD) ...polycrystalline diamond film was used to fabricate a micro‐detector owing to its well controlled size, good thermostability, and appropriate conductivity. The preparation process and the main components of the CVD diamond micro‐detector are described. The external dimensions of the packaged CVD diamond micro‐detector are 15 mm × 7.8 mm × 5.8 mm. To demonstrate the performance of the detector, K‐edge X‐ray absorption fine‐structure (XAFS) spectra of Cr, Fe, Cu, and Se foils were collected using the CVD diamond micro‐detector and routine ion chamber. These XAFS measurements were performed at beamline 1W2B of Beijing Synchrotron Radiation Facility, covering an energy range from 5.5 to 13.5 keV. By comparison, it can be seen that the CVD diamond micro‐detector shows a more excellent performance than the routine ion‐chamber in recording these XAFS spectra. The successful application of the CVD diamond micro‐detector in XAFS measurements shows its feasibility in recording X‐ray intensity.
A polycrystalline diamond detector for XAFS measurement has been fabricated. Its volume is 2947 times smaller than a routine ion‐chamber.
As a candidate anode material for Li-ion batteries, Bi-based materials have attracted extensive attention from researchers due to their high specific capacity, environmental friendliness, and simple ...synthesis methods. However, Bi-based anode materials are prone to causing large volume changes during charging and discharging processes, and the effect of these changes on lithium storage performance is still unclear. This work introduces that Bi/C nanocomposites are prepared by the Bi-based MOF precursor calcination method, and that the Bi/C nanocomposite maintains a high specific capacity (931.6 mAh g
) with good multiplicative performance after 100 cycles at a current density of 100 mA g
. The structural evolution of Bi/C anode material during the first cycle of charging and discharging is investigated using in situ synchrotron radiation SAXS. The SAXS results indicate that the multistage scatterers of Bi/C composite, used as an anode material during the first lithiation, can be classified into mesopores, interspaces, and Bi nanoparticles. The different nanostructure evolutions of three types of Bi nanoparticles were observed. It is believed that this result will help to further understand the complex reaction mechanism of Bi-based anode materials in Li-ion batteries.
With the increasing energy demands for electronic devices and electrical vehicles, anode materials for lithium ion batteries (LIBs) with high specific capacity, good cyclic and rate performances ...become one of the focal areas of research. SnO
2
has been studied as a promising anode material for LIBs due to its high theoretical capacity. However, the large volume expansion and severe structural collapse during cycles are serious. SnO
2
/graphene composite is fabricated as LIBs anode material and systematically investigated by XRD, SEM, XPS, and SAXS. The nanostructural evolutions of SnO
2
nanoparticles and SnO
2
/graphene nanocomposite as anode materials are studied during the first and the tenth discharges by in situ electrochemical-SAXS technique. During the first to the tenth discharges, the SnO
2
nanospheres tended to pulverize after expanding. The SnO
2
/graphene composite also expanded after discharge, but it didn’t pulverize immediately after the tenth discharge. SAXS results also demonstrated that the multihierarchical scatterers in the anode materials can be roughly divided into gap, interspace, SnO
2
nanoparticles, nanopores and so on. These results suggested that this composite structure can buffer large volume changes and effectively prevent the detachment and pulverization of SnO
2
during the lithiation and delithiation processes. This research is of great significance for exploring energy storage materials for LIBs with higher stable cycling performance.
Electrocatalytic CO
2
reduction (ECR) offers an attractive approach to realizing carbon neutrality and producing valuable chemicals and fuels using CO
2
as the feedstock. However, the lack of ...cost-effective electrocatalysts with better performances has seriously hindered its application. Herein, a one-step co-electrodeposition method was used to introduce Zn, a metal with weak *CO binding energy, into Cu to form Cu/Zn intermetallic catalysts (Cu/Zn IMCs). It was shown that, using an H-cell, the high Faradaic efficiency of C
2+
hydrocarbons/alcohols
(
FE
C
2
+
)
could be achieved in ECR by adjusting the surface metal components and the applied potential. In suitable conditions, FE
C2+
and current density could be as high as 75% and 40 mA/cm
2
, respectively. Compared with the Cu catalyst, the Cu/Zn IMCs have a lower interfacial charge transfer resistance and a larger electrochemically active surface area (ECSA), which accelerate the reaction. Moreover, the *CO formed on Zn sites can move to Cu sites due to its weak binding with *CO, and thus enhance the C–C coupling on the Cu surface to form C
2+
products.
► The hydrothermal synthesis is used to prepare Co-doped ZnO nanomaterials. ► XRD, XAFS and DAFS techniques are used to characterize the structures of Co-doped ZnO. ► The doped Co atoms in ZnO ...nanoparticles exhibit Co2+ and Co3+, and the Co3+ occupies the surface Zn vacancy sites. ► The occupancy of Co2+ to Co3+ tends to 1/3 with the increase of the Co-doped concentration x.
Co-doped Zn1−xCoxO nanoparticles were prepared by hydrothermal synthesis. The morphology, solid solubility and local atomic structure around the doping Co atoms were investigated. The morphologies of Co-doped ZnO nanoparticles were observed by scanning electron microscopy. The crystal structure of nanoparticles and the possible impurity phase were analyzed by X-ray diffraction patterns. The local atomic arrangements were studied by X-ray absorption fine structure spectroscopy. The substitution of Co for Zn was confirmed by diffraction anomalous fine structure spectra. The results demonstrated that Zn1−xCoxO can form a single phase of Co-doped ZnO with x⩽0.03. But it is a mixture of Co-doped ZnO and Co(OH)2 phases with x⩾0.05. Hydrothermal temperature can decrease the solid solubility of Co in ZnO lattice. Polar molecules can control the morphology of the nanoparticles. The Co-doped ZnO nanoparticles take a rod-like shape and the axial direction of the nanorods is along the c-axis direction of hexagonal wurtzite unit cell. A mixed-valence state of Co2+ and Co3+ is identified for the Co-doped ZnO nanoparticles. Diffraction anomalous fine structure technique could be used to determine the solid solubility of impurity when only one equivalent crystalline site in the host crystal is replaced by the impurity atoms. The Co-doped ZnO particles were identified to have room-temperature ferromagnetic properties.
The electrochemical CO2 reduction reaction (CO2RR) is a promising approach for mitigating the greenhouse effect arising from anthropogenic CO2 emission. Nonetheless, poor product selectivity ...associated with electrochemical catalysts is the main technical problem for the application of CO2RR technology. The catalytic performance of nano-catalysts is strongly dependent on their microstructural features. Anomalous small-angle X-ray scattering (ASAXS) is one of the most effective techniques for studying nanostructural change in an operando way, especially for complex systems and mixed-element catalyst situations. Furthermore, based on the research results of ASAXS, appropriate catalyst components and nanostructures can be designed to achieve stable catalytic performance of the catalyst, promote catalytic reaction rate, or improve catalytic reaction selectivity. In this paper, the basic concept, principle, and applications in different systems of ASAXS are reviewed thoroughly. Finally, the development prospect of ASAXS in the field of electrocatalysis is prospected. It is hoped that this review will further promote ASAXS technology to play a more far-reaching impact in the field of electrocatalytic CO2RR.
•A pulse discharge method was used to synthesize noncrystalline Ni-P nanoparticles.•Size controlled nanoparticles were prepared through adjustment of reaction parameters.•Local structures both ...centered around Ni and P atoms were investigated including coordinated atoms and bondlengths.•Magnetic properties of the nickel phosphide nanoparticles are found to be ferromagnetic and size-dependent.
Pulse discharge method was used in liquid phase to prepare nickel phosphide nanoparticles. The size and morphology of the as-prepared nanoparticles were found to be easily controlled through changing reaction parameters such as temperature, reactants concentration, reactants molar ratio, pulse discharge number, and pulse discharge voltage. The optimal reaction parameters have been obtained by single-factor experiments. X-ray diffraction, X-ray absorption fine structure spectra, Field Emission Scanning Electron Microscope, and Energy Dispersive X-ray Spectrum were used to characterize the as-prepared Ni–P nanoparticles. Vibrating Sample Magnetometer was used as magnetic measurements of the Ni–P nanoparticles. The results demonstrate that the as-prepared Ni–P nanoparticles are in amorphous phase, and consist of Ni and P elements. The P-content in the as-prepared Ni–P nanoparticles increases with the increasing of Ni–P particle size, and is independent on the initial concentration of P-concentration in the reaction solution. The Ni–P nanoparticles have totally about 12 near-neighbors of Ni–Ni and Ni–P around center Ni. The Ni–Ni distance increases with the increasing particle size. The as-prepared Ni–P nanoparticles present paramagnetic nature. Their saturated magnetizations are also size-dependent. The larger Ni–P particles has lower saturated magnetization, which can be attributed to the entrance of P into Ni lattice, causing a larger Ni–Ni separation and a looser, distorted local atomic structure.
