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.

In-situ elemental reaction-regulated Ag_(2)S films enable the best thermoelectric performances

Silver sulfide thinfilm,with excellent thermoelectric properties,is few reported due to the complex and time-consuming high-temperature or high-pressure synthesis process.Here,a fast ionic conductor n-type Ag2Sfilm with good crystallinity and uniform density is prepared by sputtering metal Agfilms of different thicknesses on glass and then reacting in S precursor solution at low temperature.At 450 K,β-Ag2Sfilms can be obtained and underwent a phase transition fromα-Ag2S monoclinic,which had a significant effect on their electrical and thermal properties.The grain size of Ag2Sfilms increases with the increase offilm thickness.Before and after the phase transition,the carrier concentration and mobility cause obvious changes in the electrical properties of Ag2S.The carrier concentration of body-centered cubic phaseβ-Ag2S is about three orders of magnitude higher than that of monoclinic phaseα-Ag2S,and the mobility is also 2–3 times that of the latter.Especially,after the phase transition,the conductivity ofβ-Ag2S rises exponentially from the zero conductivity ofα-Ag2S and increases with the increase of temperature.The Ag2Sfilm shows the highestfigure of merit of 0.830.30 at 600 K from the sample with±∼1600 nm thickness,which is the highest record among Ag2S-based thermoelectric materials reported so far.

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.

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.

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.

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.

MICHAEL REACTION OF CHLOROESTERS IN A TWO-PHASE SOLID-LIQUID SYSTEM

The Michael addition of α-chloroesters to α,β-unsaturated systems was catalyzed bytraalkylammonium salt in a two-phase solid-liquid system, and some polysubstitnted evclopropanes were facilely synthesized.

A Review of In‑Situ Techniques for Probing Active Sites and Mechanisms of Electrocatalytic Oxygen Reduction Reactions

Electrocatalytic oxygen reduction reaction(ORR)is one of the most important reactions in electrochemical energy technologies such as fuel cells and metal–O2/air batteries,etc.However,the essential catalysts to overcome its slow reaction kinetic always undergo a complex dynamic evolution in the actual catalytic process,and the concomitant intermediates and catalytic products also occur continuous conversion and reconstruction.This makes them difficult to be accurately captured,making the identification of ORR active sites and the elucidation of ORR mechanisms difficult.Thus,it is necessary to use extensive in-situ characterization techniques to proceed the real-time monitoring of the catalyst structure and the evolution state of intermediates and products during ORR.This work reviews the major advances in the use of various in-situ techniques to characterize the catalytic processes of various catalysts.Specifically,the catalyst structure evolutions revealed directly by in-situ techniques are systematically summarized,such as phase,valence,electronic transfer,coordination,and spin states varies.In-situ revelation of intermediate adsorption/desorption behavior,and the real-time monitoring of the product nucleation,growth,and reconstruction evolution are equally emphasized in the discussion.Other interference factors,as well as in-situ signal assignment with the aid of theoretical calculations,are also covered.Finally,some major challenges and prospects of in-situ techniques for future catalysts research in the ORR process are proposed.

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.

In-situ magnetic field enhanced performances in ferromagnetic FeCo_(2)O_(4) nanofibers-based rechargeable Zinc-air batteries

Field-assisted electrocatalytic reactions are demonstrated to be sufficient strategies in enhancing the electrocatalyst activities for oxygen evolution reaction(OER).Here,we report the in-situ magnetic field enhanced electrocatalytic activity in ferromagnetic FeCo_(2)O_(4)nanofibers.Our results demonstrate that the overpotential of FeCo_(2)O_(4)nanofibers at 10 mA cm^(-2)shows a left-shift of 40 mV for the OER by applying an external magnetic field,and no obvious change has been observed in the non-ferromagnetic-order Co3O4nanofibers.Calculation results indicate that there are more overlaps between the density of states for Co3d and O 2p by applying an external magnetic field.Accordingly,the spin hybridization of 3d-2p and the kinetics of spin charge transfer are optimized in ferromagnetic FeCo_(2)O_(4),which can promote the adsorption of oxygen-intermediates and electron transfer,significantly improving its electrocatalytic efficiency.What’s more,the maximum power density of the FeCo_(2)O_(4)nanofibers based Zn-air battery(ZAB)increases from 97.3 mW cm^(-2)to 108.2 mW cm^(-2)by applying an external magnetic field,providing a new idea for the application of magnetic cathode electrocatalysts in ZABs.

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.

REACTION OF ETHYL N-CYANOMETHYLBENZEHECARBOXIMIDATE WITH ALIPHATIC ALDEHYDES UNDER THE SOLID-LIQUID PHASE TRANSFER CATALYSIS

Ethyl N-cyanomethytbenzenecarboximidate reacted with aliphatic aldehydes under the solid-liquid PTC condition to gire a-ethoxyphenylmethylene- aminoacrylonitrile derivatives and oxazoline derivatives.It is a convenient and new method for synthesis of β,β'-dihyroxy-a-amino acids by hydrolysis of the oxazoline derivatives.

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.