Recent advances and key perspectives of in-situ studies for oxygen evolution reaction in water electrolysis

Electricity-driven water splitting to produce hydrogen is one of the most efficient ways to alleviate energy crisis and environmental pollution problems,in which the anodic oxygen evolution reaction(OER)is the key half-reaction of performance-limiting in water splitting.Given the complicated reaction process and surface reconstruction of the involved catalysts under actual working conditions,unraveling the real active sites,probing multiple reaction intermediates and clarifying catalytic pathways through in-situ characterization techniques and theoretical calculations are essential.In this review,we summarize the recent advancements in understanding the catalytic process,unlocking the water oxidation active phase and elucidating catalytic mechanism of water oxidation by various in-situ characterization techniques.Firstly,we introduce conventionally proposed traditional catalytic mechanisms and novel evolutionary mechanisms of OER,and highlight the significance of optimal catalytic pathways and intrinsic stability.Next,we provide a comprehensive overview of the fundamental working principles,different detection modes,applicable scenarios,and limitations associated with the in-situ characterization techniques.Further,we exemplified the in-situ studies and discussed phase transition detection,visualization of speciation evolution,electronic structure tracking,observation of reaction active intermediates,and monitoring of catalytic products,as well as establishing catalytic structure-activity relationships and catalytic mechanism.Finally,the key challenges and future perspectives for demystifying the water oxidation process are briefly proposed.

Highly mass activity electrocatalysts with ultralow Pt loading on carbon black for hydrogen evolution reaction

Pt-based nanocatalysts offer excellent prospects for various industries.However,the low loading of Pt with excellent performance for efficient and stable nanocatalysts still presents a considerable challenge.In this study,nanocatalysts with ultralow Pt content,excellent performance,and carbon black as support were prepared through in-situ synthesis.These~2-nm particles uniformly and stably dispersed on carbon black because of the strong s-p-d orbital hybridizations between carbon black and Pt,which suppressed the agglomeration of Pt ions.This unique structure is beneficial for the hydrogen evolution reaction.The catalysts exhibited remarkable catalytic activity for hydrogen evolution reaction,exhibiting a potential of 100 mV at 100 mA·cm^(-2),which is comparable to those of commercial Pt/C catalysts.Mass activity(1.61 A/mg)was four times that of a commercial Pt/C catalyst(0.37 A/mg).The ultralow Pt loading(6.84wt%)paves the way for the development of next-generation electrocatalysts.

Stereoselective Aldol Reaction in Aqueous Solution Using Prolinamido-Glycosides as Water-Compatible Organocatalyst

Prolinamido-glycoside catalyzed asymmetric aldol reaction in aqueous media is reported. The reactions are rapid and highly stereoselective when water is used as solvent. The stereoselectivities were under influence of configurations of a prolyl residue of the catalyst and α-chiral aldehydes. Water soluble prolinamido-glycoside catalysts are easily separable from reaction mixture and can be recycled and re-used several times.

Preparation and wear properties of TiB_2/Al-30Si composites via in-situ melt reactions under high-energy ultrasonic field

TiB2/Al-30Si composites were fabricated via in-situ melt reaction under high-energy ultrasonic field. The microstructure and wear properties of the composite were investigated by XRD, SEM and dry sliding testing. The results indicate that TiB2 reinforcement particles are uniformly distributed in the aluminum matrix under high-energy ultrasonic field. The morphology of the TiB2 particles is in circle-shape or quadrangle-shape, and the size of the particles is 0.1-1.5μm. The primary silicon particles are in quadrangle-shape and the average size of them is about 10μm. Hardness values of the Al-30Si matrix alloy and the TiB2/Al-30Si composites considerably increase as the high energy ultrasonic power increases. In particular, the maximum hardness value of the in-situ composites is about 1.3 times as high as that of the matrix alloy when the ultrasonic power is 1.2 kW, reaching 412 MPa. Meanwhile, the wear resistance of the in-situ TiB2/Al-30Si composites prepared under high-energy ultrasonic field is obviously improved and is insensitive to the applied loads of the dry sliding testing.

In-situ self-templated preparation of porous core-shell Fe_(1-x)S@N,S co-doped carbon architecture for highly efficient oxygen reduction reaction

Transition metal compound(TMC)/carbon hybrids,as prospering electrocatalyst,have attracted great attention in the field of oxygen reduction reaction(ORR).Their morphology,structure and composition often play a crucial role in determining the ORR performance.In this work,we for the first time report the successful fabrication of porous core-shell Fe_(1-x)S@N,S co-doped carbon(Fe_(1-x)S@NSC-t,t represents etching time)by a novel in-situ self-template induced strategy using Fe3O4 nanospheres and pyrrole as sacrificial self-template.The post-polymerization of pyrrole can be accomplished by the Fe^(3+)released through the etching of Fe_(3)O_(4) by HCl acid.Thus,the etching time has a significant effect on the morphology,structure,composition a nd ORR performance of Fe_(1-x)S@NSC-t.Based on the cha racterizations,we find Fe_(1-x)S@NSC-24 can realize effective and balanced combination of Fe_(1-x)S and NSC,possessing porous core-shell architecture,optimized structure defect,specific surface area and doped heteroatoms configurations(especially for pyridinic N,graphitic N and Fe-N structure).These features thus lead to outstanding catalytic activity and cycling stability towards ORR.Our work provides a good guidance on the design of TMC/carbon-based electrodes with unique stable morphology and optimized structure and composition.

In-situ monitoring of dynamic behavior of catalyst materials and reaction intermediates in semiconductor catalytic processes

Semiconductor photocatalysis, as a key part of solar energy utilization, has far-reaching implications for industrial, agricultural, and commercial development. Lack of understanding of the catalyst evolution and the reaction mechanism is a critical obstacle for designing efficient and stable photocatalysts. This review summarizes the recent progress of in-situ exploring the dynamic behavior of catalyst materials and reaction intermediates. Semiconductor photocatalytic processes and two major classes of in-situ techniques that include microscopic imaging and spectroscopic characterization are presented. Finally, problems and challenges in in-situ characterization are proposed, geared toward developing more advanced in-situ techniques and monitoring more accurate and realistic reaction processes, to guide designing advanced photocatalysts.

Dense copper azide synthesized by in-situ reaction of assembled nanoporous copper microspheres and its initiation performance

Copper azide with high density was successfully synthesized by in-situ reaction of nanoporous copper(NPC)precursor with HN_(3) gaseous.NPC with pore size of about 529 nm has been prepared by electroless plating using polystyrene(PS)as templates.The copper shells thickness of NPC was controlled by adjusting the PS loading amount.The effects of copper shell on the morphology,structure and density of copper azide were investigated.The conversion increased from 87.12%to 95.31%when copper shell thickness decrease from 100 to 50 nm.Meanwhile,the density of copper azide prepared by 529 nm NPC for 24 h was up to 2.38 g/cm^(3).The hollow structure of this NPC was filled by swelling of copper azide which guaranteed enough filling volume for keeping the same shape as well as improving the charge density.Moreover,HNS-IV explosive was successfully initiated by copper azide with minimum charge thickness of 0.55 mm,showing that copper azide prepared has excellent initiation performance,which has more advantages in the application of miniaturized explosive systems.

Visualization of atomic scale reaction dynamics of supported nanocatalysts during oxidation and ammonia synthesis using in-situ environmental(scanning) transmission electron microscopy

Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst function.Supported noble metal nanocatalysts such as platinum are of interest in fuel cells and as diesel oxidation catalysts for pollution control,and practical ruthenium nanocatalysts are explored for ammonia synthesis.Graphite and graphitic carbons are of interest as supports for the nanocatalysts.Despite considerable literature on the catalytic processes on graphite and graphitic supports,reaction dynamics of the nanocatalysts on the supports in different reactive gas environments and operating temperatures at the single atom level are not well understood.Here we present real time in-situ observations and analyses of reaction dynamics of Pt in oxidation,and practical Ru nanocatalysts in ammonia synthesis,on graphite and related supports under controlled reaction environments using a novel in-situ environmental(scanning) transmission electron microscope with single atom resolution.By recording snapshots of the reaction dynamics,the behaviour of the catalysts is imaged.The images reveal single metal atoms,clusters of a few atoms on the graphitic supports and the support function.These all play key roles in the mobility,sintering and growth of the catalysts.The experimental findings provide new structural insights into atomic scale reaction dynamics,morphology and stability of the nanocatalysts.

Microstructure and Properties of A IN Coating/Graphite Fabricated via In-situ Reaction

A novel method was used to fabricate AlN coating on graphite substrate. This approach included two steps： firstly, the emulsion composed of BN and anhydrous ethanol was sprayed on the surface of the graphite substrate; secondly, AlN coating was formed through the in-situ reaction of Al with the sprayed BN. The reaction was investigated by thermogravimetric-differential thermal analysis （TG-DTA）, and the phase composition in the synthetic process was characterized by X-ray diffraction （XRD）. Scanning electronic microscopy （SEM） was used to observe the morphology, and electron probe microanalysis （EPMA） was used to observe the distribution of the elements. The experimental results show that the AlN coating is dense and bonded with graphite tightly.

PARTICLES ANALYSIS OF Al_2O_3 PARTICLE REINFORCED ZL202 MATRIX COMPOSITES PREPARED BY IN-SITU REACTION

ZL202 matrix composite reinforced by Al2O3 particles was prepared by combining in-situ reaction and casting techniques. Particles' size in the composites was from 1 to 5 microns in diameter. X-ray diffraction analysis verified that the reinforcing particleswere δ-Al2O3 which belong to γ-Al2O3 series. The wetting angle between matrix andreinforcement was less than 90°. Energy spectrum analysis indicated that the reactionin bell cover pressing process took place not so completely as in flouring stir process. When the reaction was finished, the matrix was still ZL202 alloy in both.processes.

Microstructure and Mechanical Property of (TiNbTaZrHf)C Synthesized by In-situ Reaction

The(TiNbTaZrHf)C high entropy carbide(HEC)was successfully synthesized by complete commercial transition metal powders,obtained fine sintered bulks without additives by in-situ reaction element synthesis method.(TiNbTaZrHf)C bulk shows a face centered cubic rock salt structure with homogeneous single-phase FCC structure in composition and structure.The optimum sintering temperature is about 1900℃at which the best mechanical properties are obtained.The mechanical properties of(TiNbTaZrHf)C ceramic block are better than those of binary transition metal carbides,and it has obvious high entropy effect.Adding a small amount of Al as sintering additive,the mechanical properties of(TiNbTaZrHf)C ceramics continue to improve,the bending strength of the samples at each temperature is increased by at least 38%,and the highest is 486 MPa.The elastic modulus and hardness of the sample at 1900℃are also slightly increased by 4%and 14%,respectively.The above conclusions illustrate that the properties of high entropy ceramics are greatly improved by in-situ reaction sintering.

Microstructure and mechanical properties of Fe/NbC composite layer prepared by in-situ reaction

NbC ceramic surface-reinforced steel matrix composites were prepared by an in-situ reaction method at different temperatures(1,050℃,1,100℃and 1,150℃)for different times(1 h,2 h and 3 h).The phase constitution,microstructure and fracture morphology of NbC ceramic surface-reinforced steel matrix composites were analyzed by XRD,SEM and EDS,and the effects of the in-situ reaction temperature and time on the mechanical properties were systematically studied.The results indicate that the NbC reinforcement layer is formed through the reaction between Nb atoms and carbon atoms diffused from the steel matrix to the Nb plate.The thickness of this reinforcement layer increases as the reaction time prolongs.Additionally,an increase in reaction temperature results in a thicker reinforcement layer,although the rate of increase gradually decreases.The relationship among the thickness of the Nb C reinforcement layer,the reaction time and temperature was established by data fitting.The optimal tensile performance is achieved at 1,100℃for 1 h,with a tensile strength of 228 MPa.It is also found that the defects between the reinforcement layer and the steel matrix are related to reaction temperature.At 1,100℃,these defects are minimal.Fracture mostly occurs in the NbC reinforced layer of the composites,and the fracture mode is characterized by typical intergranular brittle fracture.

Eutectic Solution Enables Powerful Click Reaction for In-Situ Construction of Advanced Gel Electrolytes

Thiol-ene click reaction is an intriguing strategy for preparing polymer electrolytes due to its high activity,atom economy and less side reaction.However,the explosive reaction rate and the use of non-electrolytic amine catalyst hamper its application in in-situ batteries.Herein,a nitrogen-containing eutectic solution is designed as both the catalyst of the thiol-ene reaction and the plasticizer to in-situ synthesize the gel polymer electrolytes,realizing a mild in-situ gelation process and the preparation of high-performance gel electrolytes.The obtained gel polymer electrolytes exhibit a high ionic conductivity of 4×10^(−4)S cm^(−1)and lithium-ion transference number(t_(Li)^(+))of 0.51 at 60°C.The as-assembled Li/LiFePO_(4)(LFP)cell delivers a high initial discharge capacity of 155.9 mAh g^(-1),and a favorable cycling stability with the capacity retention of 82%after 800 cycles at 1 C is also obtained.In addition,this eutectic solution significantly improves the rate performance of the LFP cell with high specific capacity of 141.5 and 126.8 mAh g^(-1)at 5 C and 10 C,respectively,and the cell can steadily work at various charge–discharge rate for 200 cycles.This powerful and efficient strategy may provide a novel way for in-situ preparing gel polymer electrolytes with desirable comprehensive performances.

In-situ Preparation of Al/TiAl_3(P) Composite by Direct Reaction between Molten Al and TiO_2 Powder

TiAl3 particle reinforced pure Al composite has been made by direct reaction among molten Al, TiO2 and a flux. The composite exhibits high Synthetically properties. The strength and hardness are higher than those of pure Al matrix by 71.5% and 134% respectively However, the elongation is 20.36%, slightly lower than that of the Al matrix.

Compatible stability study of Xing NaoJing injection based on physical-chemical properties analysis

Objective:The clinical treatment of brain diseases is urgent. Xingnaojing (XNJ) injection is often used in combination with other injection drugs. Due to the possible interaction between the injections in vivo, the particle size, osmotic pressure, pH value change and component stability decrease, that is one of the important factors causing various adverse reactions. Based on the above situation, this study investigated the physical properties and chemical composition changes of XNJ injection and its compatibility solvent and 13 kinds of clinical injection, speculated the possible interactions between the drugs in vivo from the perspective of in vitro compatibility stability, find out the safety risks of adverse reactions and provide guidance for the safe and rational use of XNJ injection. Methods:According to the clinical application, XNJ injection was mixed with 13 combination injections based on 250 mL 5% glucose injection, and placed at room temperature for 6 h. Then, the clarity, particle size, pH, osmolality, and the contents of camphor, d-borneol, and muscone of the compatible solutions were detected at 0, 1, 2, 4, and 6 h, respectively. Results:The results showed that the physical-chemical properties of compatibility solution were slightly influenced when XNJ was combined with Alprostadil injection and Danhong injection. The change of particle size and the degradation of muscone content were the main factors affecting the compatibility stability of XNJ injection, indicating that there are some problems in compatibility stability, which may be one of the causes of clinical adverse reactions. Conclusion:This study suggests that XNJ injection in combination with other injections during intravenous administration should be performed cautiously.

A review of in-situ high-temperature characterizations for understanding the processes in metallurgical engineering

For the rational manipulation of the production quality of high-temperature metallurgical engineering,there are many challenges in understanding the processes involved because of the black box chemical/electrochemical reactors.To overcome this issue,various in-situ characterization methods have been recently developed to analyze the interactions between the composition,microstructure,and solid-liquid interface of high-temperature electrochemical electrodes and molten salts.In this review,recent progress of in-situ hightemperature characterization techniques is discussed to summarize the advances in understanding the processes in metallurgical engineering.In-situ high-temperature technologies and analytical methods mainly include synchrotron X-ray diffraction(s-XRD),laser scanning confocal microscopy,and X-ray computed microtomography(X-rayμ-CT),which are important platforms for analyzing the structure and morphology of the electrodes to reveal the complexity and variability of their interfaces.In addition,laser-induced breakdown spectroscopy,high-temperature Raman spectroscopy,and ultraviolet-visible absorption spectroscopy provide microscale characterizations of the composition and structure of molten salts.More importantly,the combination of X-rayμ-CT and s-XRD techniques enables the investigation of the chemical reaction mechanisms at the two-phase interface.Therefore,these in-situ methods are essential for analyzing the chemical/electrochemical kinetics of high-temperature reaction processes and establishing the theoretical principles for the efficient and stable operation of chemical/electrochemical metallurgical processes.

Progress in in-situ electrochemical nuclear magnetic resonance for battery research

A thorough understanding of the fundamental electrochemical and chemical processes in batteries is crucial to advancing energy density and power density.However,the characterizations of such processes are complex.In-situ electrochemical nuclear magnetic resonance(EC-NMR)offers the capability to collect real-time data during battery operation,furnishing insights into the local structures and ionic dynamics of materials by monitoring changes in the chemical environment around the nuclei.EC-NMR also has the advantages of being both quantitative and non-destructive.This paper systematically reviews the design of EC-NMR approach,and delves into the applications and progress of EC-NMR concerning battery reaction mechanisms,failure mechanisms,and overall battery systems.The review culminates in a comprehensive summary of the perspective and challenges associated with EC-NMR.

In-situ synthesis of Al_3Ti particles reinforced Al-based composite coating

Using titanium wires （99.5%, 200 μm in diameter） as a reactive source, an Al-based composite coating reinforced by titanium tri-aluminide （A13Ti） particles was fabricated by infiltration plus in-situ methods. According to the differential thermal analysis （DTA） curve, the reactive temperature between Ti wires and A1 matrix can be determined at 890 ℃. The obtained composite coatings were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and microhardness and wear test. The experimental results show that when holding period is 20 min at 890℃, the titanium wires react completely to in-situ synthesize Al3Ti particles, which presents blocky and strip-like states. The microhardness of in-situ synthesized Al3Ti particles is about 4.5 times that of the Al-matrix. Under the condition of dry sliding at 10 N load, compared with the unreinforced Al matrix, the composite coating fabricated with 20 min offers unique wear resistance behavior, and its wear mechanism is that the adhesive wear and abrasive wear coexist.

Microstructural aspects of in-situ TiB reinforced Ti-6Al-4V composite processed by spark plasma sintering

Titanium-matrix composites have important and wide applications in the transport and aerospace industries. The current research was focused on powder metallurgy processing of in-situ reinforced titanium-matrix composite with Ti B whiskers. The Ti-6Al-4V alloy and B4 C additive powders were used as raw materials. Two different consolidation techniques, namely press-and-sintering and spark plasma sintering, were selected. It was observed that in-situ Ti B whiskers were formed during sintering in both methods. The changes in size, aspect ratio and distribution of in-situ whiskers in different composite samples were monitored. The effect of spark plasma sintering temperature on the synthesis of in-situ whiskers was also investigated. Based on the microstructural observations（optical microscopy and scanning electron microscopy） and the energy dispersive spectroscopy analysis, it was concluded that increasing the spark plasma sintering temperature from 900 to 1100 °C would lead to the complete formation of in-situ Ti B whiskers and reduced porosity content.

Growth mechanism of reinforcements in in-situ synthesized (TiB+TiC)/Ti composites

The growth mechanism of reinforcement in in situ synthesized (TiB+TiC)/Ti composites was investigated. The results show that reinforcements nucleate and grow in a way of dissolution precipitation. The morphologies of reinforcements are closely related to the solidification paths and crystal structure of reinforcements. TiB, as a reinforcement, is liable to grow along [010] direction and forms in short fibre shape due to its B27 structure, whereas primary TiC is liable to form composition undercooling and grow in dendritic shape. TiC phases precipitated in binary eutectic and ternary eutectic reactions grow in equiaxial shape. The addition of aluminum element refines TiB and TiC particles, and makes TiC reinforcements grow into the equiaxial particles easily. The addition of graphite adjusts the solidification paths and forms more TiC with dendritic shape. [