Biochar is a reactive carrier as it may be partially gasified with steam in steam reforming,which could influence the formation of reaction intermediates and modify catalytic behaviors.Herein,the Ni/biochar as well as...Biochar is a reactive carrier as it may be partially gasified with steam in steam reforming,which could influence the formation of reaction intermediates and modify catalytic behaviors.Herein,the Ni/biochar as well as two comparative catalysts,Ni/Al_(2)O_(3) and Ni/SiO_(2),with low nickel loading(2%(mass))was conducted to probe involvement of the varied carriers in the steam reforming.The results indicated that the Ni/biochar performed excellent catalytic activity than Ni/SiO_(2) and Ni/Al_(2)O_(3),as the biochar carrier facilitated quick conversion of the -OH from dissociation of steam to gasify the oxygen-rich carbonaceous intermediates like C=O and C-O-C,resulting in low coverage while high exposure of nickel species for maintaining the superior catalytic performance.In converse,strong adsorption of aliphatic intermediates over Ni/Al_(2)O_(3) and Ni/SiO_(2) induced serious coking with polymeric coke as the main type(21.5%and 32.1%,respectively),which was significantly higher than that over Ni/biochar(3.9%).The coke over Ni/biochar was mainly aromatic or catalytic type with nanotube morphology and high crystallinity.The high resistivity of Ni/biochar towards coking was due to the balance between formation of coke and gasification of coke and partially biochar with steam,which created developed mesopores in spent Ni/biochar while the coke blocked pores in Ni/Al_(2)O_(3) and Ni/SiO_(2) catalysts.展开更多
Detection and observation of reactive intermediates is an essential step in investigation of reaction pathways.However,most reactive intermediates are unstable and present at low concentrations;their short lifetimes m...Detection and observation of reactive intermediates is an essential step in investigation of reaction pathways.However,most reactive intermediates are unstable and present at low concentrations;their short lifetimes make them difficult to detect and characterize.Supramolecular containers offer opportunities for the stabilization and characterization of those labile species,through isolation from the media and protection inside the cavity of the host.In this review,we summarize the examples of labile reaction intermediates that are stabilized and characterized with the help of supramolecular containers.The container compounds include carcerands,deep cavitands and amide naphthotubes.We focus on unstable vip species-cyclobutadiene,benzocyclopropenone,o-benzyne,1,2,4,6-cycloheptatetraene,anti-Bredt's olefin,fluorophenoxycarbene,O-acylisoamide,and hemiaminalthat act as intermediates in certain organic reactions.展开更多
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 ...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.展开更多
A novel Ag-alumina hybrid surface-enhanced Raman spectroscopy （SERS） platform has been designed for the spectroscopic detection of surface reactions in the steady state. Single crystalline and faceted silver （Ag） ...A novel Ag-alumina hybrid surface-enhanced Raman spectroscopy （SERS） platform has been designed for the spectroscopic detection of surface reactions in the steady state. Single crystalline and faceted silver （Ag） nanoparticles with strong light scattering were prepared in large quantity, which enables their reproducible self-assembly into large scale monolayers of Raman sensor arrays by the Langrnuir-Blodgett technique. The close packed sensor film contains high density of sub-nm gaps between sharp edges of Ag nanoparticles, which created large local electromagnetic fields that serve as ＂hot spots＂ for SERS enhancement. The SERS substrate was then coated with a thin layer of alumina by atomic layer deposition to prevent charge transfer between Ag and the reaction system. The photocatalytic water splitting reaction on a monolayer of anatase TiO2 nanoplates decorated with Pt co-catalyst nanoparticles was employed as a model reaction system. Reaction intermediates of water photooxidation were observed at the TiO2/solution interface under UV irradiation. The surface-enhanced Raman vibrations corresponding to peroxo, hydroperoxo and hydroxo surface intermediate species were observed on the TiO2 surface, suggesting that the photo-oxidation of water on these anatase TiO2 nanosheets may be initiated by a nucleophilic attack mechanism.展开更多
During steam reforming,the performance of a catalyst and amount/property of coke are closely related to reaction intermediates reaching surface of a catalyst.Herein,modification of reaction intermediates by placing Mg...During steam reforming,the performance of a catalyst and amount/property of coke are closely related to reaction intermediates reaching surface of a catalyst.Herein,modification of reaction intermediates by placing Mg-Al-hydrotalcite above Ni/KIT-6 catalyst in steam reforming of glycerol was conducted at 300 to 600°C.The results revealed that the catalytic activity of Ni/KIT-6 in the lower bed was enhanced with either Mg1-Al5-hydrotalcite(containing more acidic sites)or Mg5-Al1-hydrotalcite(containing more alkaline sites)as upper-layer catalyst.The in situ infrared characterization of steam reforming demonstrated that Mg-Al-hydrotalcite catalyzed the deoxygenation of glycerol,facilitating the reforming of the partially deoxygenated intermediates over Ni/KIT-6.Mg-Al-hydrotalcite as protective catalyst,however,did not protect the Ni/KIT-6 from formation of more coke.Nonetheless,this did not lead to further deactivation of Ni/KIT-6 while Mg5-Al1-hydrotalcite even substantially enhanced the catalytic stability,even though the coke was much more significant than that in the use of single Ni/KIT-6(52.7%vs.28.6%).The reason beneath this was change of the property of coke from more aliphatic to more aromatic.Mg5-Al1-hydrotalcite catalyzed dehydration of glycerol,producing dominantly reaction intermediates bearing C=C,which formed the catalytic coke of with carbon nanotube as the main form with smooth outer walls as well as higher aromaticity,C/H ratio,crystallinity,crystal carbon size,thermal stability,and resistivity toward oxidation on Ni/KIT-6 in the lower bed.In comparison,the abundance of acidic sites on Mg1-Al5-hydrotalcite catalyzed the formation of more oxygen-containing species,leading to the formation of carbon nanotubes of rough surface on Ni/KIT-6.展开更多
In situ electron paramagnetic resonance(EPR)monitoring of the photocatalytic halogen atom transfer(XAT)reaction with organic amines has provided insights into the dynamic transformations of intermediates,including cat...In situ electron paramagnetic resonance(EPR)monitoring of the photocatalytic halogen atom transfer(XAT)reaction with organic amines has provided insights into the dynamic transformations of intermediates,including catalyst intermediate states,amine alkyl radicals,and the dehalogenation of halogenated hydrocarbons to form carbon-centered radicals.This approach facilitated the photocatalytic single-linear state oxygen-promoted halogen atom transfer quinoxalinone alkylation reaction.展开更多
The investigation of reaction kinetics is the key to understanding the nature of reaction processes.However,monitoring fast photochemical reactions by mass spectrometry remains challenging.Herein,we developed an optic...The investigation of reaction kinetics is the key to understanding the nature of reaction processes.However,monitoring fast photochemical reactions by mass spectrometry remains challenging.Herein,we developed an optical focusing inductive electrospray(OF-iESI)mass spectrometry platform for real-time and in-situ photoreaction monitoring.Coaxial irradiation from back of nanoelectrospray emitter with a taper section was utilized,so the emitter could act as optical lens to help achieving much larger optical power density at emitter tip compared to other sections,which allowed for in-situ reaction monitoring of photoreactions.Through theoretical calculations,the highest optical power density region volume was ca.45 nL.We also integrated a controller for the laser source(450 nm),enabling the modulation of pulse duration(>1 ms).This facilitates the study of photochemical reaction kinetics.The in-situ capability of this device was proved by capturing the short-lived photogenerated intermediates during the dehydrogenation of tetrahydroquinoline.This device was further used to investigate the kinetics of triplet energy transfer based Paternò-Büchi reaction.The reaction order has hitherto remained undetermined while the result of OF-iESI suggested it followed pseudo-second-order reaction kinetics.The short-lived donor-acceptor collision complex intermediate was also successfully identified by tandem mass spectrometry.展开更多
Reman spectroscopy is used as a tool to monitor the reaction between N,N'-di(pmethyl)monothioxamides and 1,3-diamine trimethylene and to detect the reaction intermediate. By observing changes of 1024 cm^(-1) C=S b...Reman spectroscopy is used as a tool to monitor the reaction between N,N'-di(pmethyl)monothioxamides and 1,3-diamine trimethylene and to detect the reaction intermediate. By observing changes of 1024 cm^(-1) C=S band and appearance of a new bend at around 1720 cm^(-1), the reaction mechanism is discussed.展开更多
Electrochemical CO2 reduction is a promising strategy for the utilization of CO2 and intermittent excess electricity.Cu is the only single metal catalyst that can electrochemically convert CO2 into multicarbon product...Electrochemical CO2 reduction is a promising strategy for the utilization of CO2 and intermittent excess electricity.Cu is the only single metal catalyst that can electrochemically convert CO2 into multicarbon products.However,Cu exhibits an unfavorable activity and selectivity for the generation of C2 products because of the insufficient amount of CO*provided for the C‐C coupling.Based on the strong CO2 adsorption and ultrafast reaction kinetics of CO*formation on Pd,an intimate CuPd(100)interface was designed to lower the intermediate reaction barriers and improve the efficiency of C2 product formation.Density functional theory(DFT)calculations showed that the CuPd(100)interface enhanced the CO2 adsorption and decreased the CO2*hydrogenation energy barrier,which was beneficial for the C‐C coupling.The potential‐determining step(PDS)barrier of CO2 to C2 products on the CuPd(100)interface was 0.61 eV,which was lower than that on Cu(100)(0.72 eV).Encouraged by the DFT calculation results,the CuPd(100)interface catalyst was prepared by a facile chemical solution method and characterized by transmission electron microscopy.CO2 temperature‐programmed desorption and gas sensor experiments further confirmed the enhancement of the CO2 adsorption and CO2*hydrogenation ability of the CuPd(100)interface catalyst.Specifically,the obtained CuPd(100)interface catalyst exhibited a C2 Faradaic efficiency of 50.3%±1.2%at‒1.4 VRHE in 0.1 M KHCO3,which was 2.1 times higher than that of the Cu catalyst(23.6%±1.5%).This study provides the basis for the rational design of Cu‐based electrocatalysts for the generation of multicarbon products by fine‐tuning the intermediate reaction barriers.展开更多
As an emergent energy carrier,ammonia benefits from a well-established industrial infrastructure for its transportation and production,positioning it as a promising candidate toward a carbon-free energy landscape.With...As an emergent energy carrier,ammonia benefits from a well-established industrial infrastructure for its transportation and production,positioning it as a promising candidate toward a carbon-free energy landscape.Within this context,the electrocatalytic ammonia oxidation reaction(AOR)is pivotal.Platinum(Pt),recognized as the most efficient AOR catalyst,has undergone extensive development over the years,yielding notable advancements across various domains,ranging from elucidating the reaction mechanism to exploring innovative materials.This review begins by elucidating the mechanism of ammonia oxidation,summarizing the evolution of the mechanism and the diverse intermediates identified through various detection methods.Subsequently,it outlines the research progress surrounding different Pt-based catalysts,followed by a discussion on standard protocols for electrochemical ammonia oxidation testing,which facilitates meaningful comparisons across studies and catalyzes the development of more efficient and potent catalysts.Moreover,the review addresses current challenges in ammonia oxidation and outlines potential future directions,providing a comprehensive outlook on the field.展开更多
Heterostructure construction has become increasingly recognized as an effective strategy to enhance oxygen evolution reaction(OER)performance due to the exposed active surfaces and improved mass/charge transfer.Inspir...Heterostructure construction has become increasingly recognized as an effective strategy to enhance oxygen evolution reaction(OER)performance due to the exposed active surfaces and improved mass/charge transfer.Inspired by natural plant structures,this study develops a unique moss-like amorphous/crystalline(CoB/CeO_(2))heterojunction.This distinctive moss-like morphology facilitates the formation of staggered sheet structures in the catalyst,providing more active sites and open channels for reaction intermediates and gas release.Benefiting from the hydrophilic properties offered by the moss-like morphology,CoB/CeO_(2) exhibits excellent OER catalytic performance in 1 M KOH,requiring only 247 mV at 100 mA cm^(-2).Physicochemical characterization and mechanistic studies reveal that the close nanoscale features between CoB and CeO_(2) create abundant binary interfaces,optimize the electronic configuration,induce changes in electronic states,and provide abundant defect sites,thereby enhancing charge transfer capabilities.This work presents a new paradigm for the design of efficient and durable OER electrocatalysts.展开更多
The ubiquitous distribution of halogenated aromatic compounds（XAr） coupled with their carcinogenicity has raised public concerns on their potential risks to both human health and the ecosystem. Recently, advanced ox...The ubiquitous distribution of halogenated aromatic compounds（XAr） coupled with their carcinogenicity has raised public concerns on their potential risks to both human health and the ecosystem. Recently, advanced oxidation processes（AOPs） have been considered as an＂environmentally-friendly＂ technology for the remediation and destruction of such recalcitrant and highly toxic XAr. During our study on the mechanism of metal-independent production of hydroxyl radicals（UOH） by halogenated quinones and H_2O_2, we found, unexpectedly, that an unprecedented UOH-dependent two-step intrinsic chemiluminescene（CL） can be produced by H_2O_2 and tetrachloro-p-benzoquinone, the major carcinogenic metabolite of the widely used wood preservative pentachlorophenol. Further investigations showed that, in all UOH-generating systems, CL can also be produced not only by pentachlorophenol and all other halogenated phenols, but also by all XAr tested. A systematic structure–activity relationship study for all 19 chlorophenolic congeners showed that the CL increased with an increasing number of Cl-substitution in general. More importantly, a relatively good correlation was observed between the formation of quinoid/semiquinone radical intermediates and CL generation. Based on these results, we propose that UOH-dependent formation of quinoid intermediates and electronically excited carbonyl species is responsible for this unusual CL production; and a rapid, sensitive,simple, and effective CL method was developed not only to detect and quantify trace amount of XAr, but also to provide useful information for predicting the toxicity or monitoring real-time degradation kinetics of XAr. These findings may have broad chemical, environmental and biological implications for future studies on halogenated aromatic persistent organic pollutants.展开更多
Simultaneously achieving high activity,selectivity and stability for electrochemical CO_(2)reduction reaction(CO_(2)RR)remains great challenges.Herein,a phosphorus-modified Sn/Sn Oxcore/shell(P-Sn/SnO_x)catalyst,deriv...Simultaneously achieving high activity,selectivity and stability for electrochemical CO_(2)reduction reaction(CO_(2)RR)remains great challenges.Herein,a phosphorus-modified Sn/Sn Oxcore/shell(P-Sn/SnO_x)catalyst,derived from in situ electrochemical reduction of an amorphous Sn(HPO_(4))_(2) pre-catalyst,exhibits high CO_(2)RR performance.The total Faradaic efficiency(FE)of C_(1) products is close to 100%in a broad potential range from-0.49 to-1.02 V vs.reversible hydrogen electrode,and a total current density of 315.0 m A cm^(-2)is achieved.Moreover,the P-Sn/SnO_(x) catalyst maintains a formate FE of~90%for 120 h.Density functional theory calculations suggest that the phosphorus-modified Sn/SnO_(x) core/shell structure effectively facilitates formate production by enhancing CO_(2)adsorption and improving free energy profile of formate formation.展开更多
he initiation mechanism of ceric ion/2-benzoyl acetanilide system was studiedby means of FT-IR, EPR and kinetic studies which revealed that 2-benzoyl ac-etanilide acts as a very active promotor to the polymerization i...he initiation mechanism of ceric ion/2-benzoyl acetanilide system was studiedby means of FT-IR, EPR and kinetic studies which revealed that 2-benzoyl ac-etanilide acts as a very active promotor to the polymerization initiated by ceric ion.The initiation mechanism was then proposed which involved the complex formationbetween a ceric ion and a l ,3-diketone group or a carbamate group, followed by,thedecomposition of the complex to generate C-centered secondary alkyl radical and N-centered anillido radical, both of which would initiate polymerization of vinylmonomer as the end groups of the polymers formed.展开更多
The production of valuable chemicals using copper(Cu)catalysts via electrochemical CO or CO_(2)reduction reactions(CORR and CO_(2)RR)has shown great potential in the field of sustainable energy conversion[1].Previous ...The production of valuable chemicals using copper(Cu)catalysts via electrochemical CO or CO_(2)reduction reactions(CORR and CO_(2)RR)has shown great potential in the field of sustainable energy conversion[1].Previous research has primarily focused on analyzing the behavior of reaction intermediates or solely on the dynamics within the solution phase,while the synergistic effects between surface species and the solution,particularly the interfacial water and its non-covalent interactions with the Cu surface,have remained partially understood[2].展开更多
Though ammonia borane NH_(3)BH_(3)(AB)was discovered in the 1950s,it is fair to state that AB as a potential chemical hydrogen storage material was discovered more recently,in the 2000s.Unlike the isoelectronic ethane...Though ammonia borane NH_(3)BH_(3)(AB)was discovered in the 1950s,it is fair to state that AB as a potential chemical hydrogen storage material was discovered more recently,in the 2000s.Unlike the isoelectronic ethane CH_(3)CH_(3),AB is polar;three of its hydrogens are protic(NH_(3)group)and the other three are hydridic(BH_(3)group);the material is solid at ambient conditions owing to dihydrogen N–H^(δ+)…H^(δ−)–B interactions;and AB decomposes from 90℃under thermogravimetric conditions.With such properties,AB has attracted much attention,even though AB in neat form is not suitable for the application mentioned above because it decomposes more than it dehydrogenates.Hence,strategies(based on solubilization,catalysis,chemical doping and nanosizing)aiming at destabilizing AB to make it release pure H_(2)at<100℃have been developed.Beyond the performance targeted for hydrogen storage,this provided us with better understanding of the mechanisms of decomposition.Indeed,studies on thermal decomposition of neat AB have revealed just how complex the mechanisms are(due to the involvement of two possible key intermediates initiating the decomposition,the formation of various volatile products,the existence of counterintuitive homopolar reactions,and the formation of polymeric residues of complex composition,for example).Studies on destabilized AB have provided insights into several mechanistic aspects including the reaction intermediates,the decomposition pathways,and the nature of the residue forming upon the release of 1 and≥2 equiv.H_(2).We presently have a fairly good understanding of the mechanisms of decomposition of AB,which is discussed in more detail below.In that respect,this review focuses firstly on the complexity of thermal decomposition of neat AB,secondly on what we know with regard to thermal decomposition of destabilized AB,and thirdly on all outstanding questions.It is very important to have an excellent knowledge of the reaction mechanisms if technological progress is to be made with AB as a chemical hydrogen storage material.展开更多
Elaborate interface engineering based on in situ surface reconstruction during catalysis,especially at the cathode,is effective at promoting the hydrogen evolution reaction(HER)but is plagued by the uncontrollable ext...Elaborate interface engineering based on in situ surface reconstruction during catalysis,especially at the cathode,is effective at promoting the hydrogen evolution reaction(HER)but is plagued by the uncontrollable extent of the reconstruction and structure collapse.In view of the reasonable adsorption of reaction intermediates and accelerating kinetics of hydroxy oxides(MOOH),we focused on the in situ structural evolution of the HER electrode toward MOOH during catalysis,which has been revealed by operando Raman spectroscopy yet seldom reported.As a typical example,Mn-doped NiS_(2)was selected as the HER electrode to monitor in situ structural evolution toward hydroxy oxides(cathode in situ-derived NiOOH,CISD-NiOOH)as Mn-NiS_(2)@CISD-NiOOH coupling catalysts.In situ formation of MOOH on the cathode is interesting.Moreover,the existence of Mn dopants renders Mn-NiS_(2)with lattice distortion and a rough surface consisting of nanoparticles of∼25 nm in diameter,differing from the smooth NiS_(2).In 1 M KOH,Mn-NiS_(2)@CISD-NiOOH exhibits a low overpotential of 330 mV to deliver 1000 mA cm^(−2)and an excellent stability of 100 h at 1300 mA cm^(−2).Notably,in alkaline seawater(1 M KOH+seawater)as well as 30%KOH industrial electrolyte,it still exhibits stable HER operation above 1000 mA cm^(−2)for at least 100 h.This study not only expands the prospects for in situ cathode structure development but also offers a robust catalytic cathode with high activity for industrial hydrogen-production systems.展开更多
The efficiency of CO_(2) photoreduction is significantly constrained by uncontrollable reaction intermediates as well as the weak adsorption and tough activation of CO_(2).Herein,we report a surface modulation strateg...The efficiency of CO_(2) photoreduction is significantly constrained by uncontrollable reaction intermediates as well as the weak adsorption and tough activation of CO_(2).Herein,we report a surface modulation strategy via hydroxyl (–OH) modification to tune the surface state of oxygen-rich-vacancy SrTiO_(3)(STO),which could efficiently optimize the structural attributes of STO,facilitating the robust generation of intermediate COOH^(*) and enhancing the surface affinity of the catalyst for CO_(2) adsorption and activation.Therefore,the CO evolution rate of the STO-OH-5 (90 μmol g^(−1)h^(−1)) catalyst is 2.6 times higher than that of the original STO (34 μmol g^(−1)h^(−1)),outperforming most other reported photocatalysts.This study elucidates the impact of surface modulation on the photocatalytic performance of STO and presents a viable strategy for the development of high-performance nanomaterial photocatalysts for CO_(2) conversion.展开更多
In this article,we investigate the dependence of nuclear temperature on emitting source neutron-proton(N/Z)asymmetry with light charged particles(LCPs)and intermediate mass fragments(IMFs)generated from intermediate-v...In this article,we investigate the dependence of nuclear temperature on emitting source neutron-proton(N/Z)asymmetry with light charged particles(LCPs)and intermediate mass fragments(IMFs)generated from intermediate-velocity sources in thirteen reaction systems with different N/Z asymmetries,^(64)Zn on^(112)Sn,and^(70)Zn,^(64)Ni on^(112,124)Sn,^(58,64)Ni,^(197)Au,and^(232)Th at 40 MeV/nucleon.The apparent temperature values of LCPs and IMFs from different systems are deduced from the measured yields using two helium-related and eight carbon-related double isotope ratio thermometers,respectively.Then,the sequential decay effect on the experimental apparent temperature deduction with the double isotope ratio thermometers is quantitatively corrected explicitly with the aid of the quantum statistical model.The present treatment is an improvement compared to our previous studies in which an indirect method was adopted to qualitatively consider the sequential decay effect.A negligible N/Z asymmetry dependence of the real temperature after the correction is quantitatively addressed in heavy-ion reactions at the present intermediate energy,where a change of o.1 units in source N/Z asymmetry corresponds to an absolute change in temperature of an order of 0.03 to 0.29 MeV on average for LCPs and IMFs.This conclusion is in close agreement with that inferred qualitatively via the indirect method in our previous studies.展开更多
基金supported by National Natural Science Foundation of China(51876080)the Program for Taishan Scholars of Shandong Province Government,the Agricultural Innovation Program of Shandong Province(SD2019NJ015)+1 种基金the Research and Development program of Shandong Basan Graphite New Material Plant,National Natural Science Foundation of China(52076097)Key projects for inter-governmental cooperation in international science,technology and innovation(2018YFE0127500).
文摘Biochar is a reactive carrier as it may be partially gasified with steam in steam reforming,which could influence the formation of reaction intermediates and modify catalytic behaviors.Herein,the Ni/biochar as well as two comparative catalysts,Ni/Al_(2)O_(3) and Ni/SiO_(2),with low nickel loading(2%(mass))was conducted to probe involvement of the varied carriers in the steam reforming.The results indicated that the Ni/biochar performed excellent catalytic activity than Ni/SiO_(2) and Ni/Al_(2)O_(3),as the biochar carrier facilitated quick conversion of the -OH from dissociation of steam to gasify the oxygen-rich carbonaceous intermediates like C=O and C-O-C,resulting in low coverage while high exposure of nickel species for maintaining the superior catalytic performance.In converse,strong adsorption of aliphatic intermediates over Ni/Al_(2)O_(3) and Ni/SiO_(2) induced serious coking with polymeric coke as the main type(21.5%and 32.1%,respectively),which was significantly higher than that over Ni/biochar(3.9%).The coke over Ni/biochar was mainly aromatic or catalytic type with nanotube morphology and high crystallinity.The high resistivity of Ni/biochar towards coking was due to the balance between formation of coke and gasification of coke and partially biochar with steam,which created developed mesopores in spent Ni/biochar while the coke blocked pores in Ni/Al_(2)O_(3) and Ni/SiO_(2) catalysts.
基金supported by the National Natural Science Foundation of China(Nos.22071144 and 22101169)Shanghai Scientific and Technological Committee(No.22010500300)。
文摘Detection and observation of reactive intermediates is an essential step in investigation of reaction pathways.However,most reactive intermediates are unstable and present at low concentrations;their short lifetimes make them difficult to detect and characterize.Supramolecular containers offer opportunities for the stabilization and characterization of those labile species,through isolation from the media and protection inside the cavity of the host.In this review,we summarize the examples of labile reaction intermediates that are stabilized and characterized with the help of supramolecular containers.The container compounds include carcerands,deep cavitands and amide naphthotubes.We focus on unstable vip species-cyclobutadiene,benzocyclopropenone,o-benzyne,1,2,4,6-cycloheptatetraene,anti-Bredt's olefin,fluorophenoxycarbene,O-acylisoamide,and hemiaminalthat act as intermediates in certain organic reactions.
基金supported by the National Science Foundation of China (21875137, 51521004, and 51420105009)Innovation Program of Shanghai Municipal Education Commission (Project No. 2019-01-07-00-02-E00069)+1 种基金the 111 Project (Project No. B16032)the fund from Center of Hydrogen Science and Joint Research Center for Clean Energy Materials at Shanghai Jiao Tong University for financial supports。
文摘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.
文摘A novel Ag-alumina hybrid surface-enhanced Raman spectroscopy （SERS） platform has been designed for the spectroscopic detection of surface reactions in the steady state. Single crystalline and faceted silver （Ag） nanoparticles with strong light scattering were prepared in large quantity, which enables their reproducible self-assembly into large scale monolayers of Raman sensor arrays by the Langrnuir-Blodgett technique. The close packed sensor film contains high density of sub-nm gaps between sharp edges of Ag nanoparticles, which created large local electromagnetic fields that serve as ＂hot spots＂ for SERS enhancement. The SERS substrate was then coated with a thin layer of alumina by atomic layer deposition to prevent charge transfer between Ag and the reaction system. The photocatalytic water splitting reaction on a monolayer of anatase TiO2 nanoplates decorated with Pt co-catalyst nanoparticles was employed as a model reaction system. Reaction intermediates of water photooxidation were observed at the TiO2/solution interface under UV irradiation. The surface-enhanced Raman vibrations corresponding to peroxo, hydroperoxo and hydroxo surface intermediate species were observed on the TiO2 surface, suggesting that the photo-oxidation of water on these anatase TiO2 nanosheets may be initiated by a nucleophilic attack mechanism.
基金supported by the National Natural Science Foundation of China(Grant No.52276195)the Program for Supporting Innovative Research of Jinan(Grant No.202228072)the Program for Agricultural Development of Shandong(Grant No.SD2019NJ015).
文摘During steam reforming,the performance of a catalyst and amount/property of coke are closely related to reaction intermediates reaching surface of a catalyst.Herein,modification of reaction intermediates by placing Mg-Al-hydrotalcite above Ni/KIT-6 catalyst in steam reforming of glycerol was conducted at 300 to 600°C.The results revealed that the catalytic activity of Ni/KIT-6 in the lower bed was enhanced with either Mg1-Al5-hydrotalcite(containing more acidic sites)or Mg5-Al1-hydrotalcite(containing more alkaline sites)as upper-layer catalyst.The in situ infrared characterization of steam reforming demonstrated that Mg-Al-hydrotalcite catalyzed the deoxygenation of glycerol,facilitating the reforming of the partially deoxygenated intermediates over Ni/KIT-6.Mg-Al-hydrotalcite as protective catalyst,however,did not protect the Ni/KIT-6 from formation of more coke.Nonetheless,this did not lead to further deactivation of Ni/KIT-6 while Mg5-Al1-hydrotalcite even substantially enhanced the catalytic stability,even though the coke was much more significant than that in the use of single Ni/KIT-6(52.7%vs.28.6%).The reason beneath this was change of the property of coke from more aliphatic to more aromatic.Mg5-Al1-hydrotalcite catalyzed dehydration of glycerol,producing dominantly reaction intermediates bearing C=C,which formed the catalytic coke of with carbon nanotube as the main form with smooth outer walls as well as higher aromaticity,C/H ratio,crystallinity,crystal carbon size,thermal stability,and resistivity toward oxidation on Ni/KIT-6 in the lower bed.In comparison,the abundance of acidic sites on Mg1-Al5-hydrotalcite catalyzed the formation of more oxygen-containing species,leading to the formation of carbon nanotubes of rough surface on Ni/KIT-6.
基金Project supported by the Domestic Visiting Fellows Program of Hangzhou Normal University(No.4095C5022521106)。
文摘In situ electron paramagnetic resonance(EPR)monitoring of the photocatalytic halogen atom transfer(XAT)reaction with organic amines has provided insights into the dynamic transformations of intermediates,including catalyst intermediate states,amine alkyl radicals,and the dehalogenation of halogenated hydrocarbons to form carbon-centered radicals.This approach facilitated the photocatalytic single-linear state oxygen-promoted halogen atom transfer quinoxalinone alkylation reaction.
基金financially supported by the National Natural Science Foundation of China(Nos.22104112 and 22374110)the Fundamental Research Funds for the Central Universities。
文摘The investigation of reaction kinetics is the key to understanding the nature of reaction processes.However,monitoring fast photochemical reactions by mass spectrometry remains challenging.Herein,we developed an optical focusing inductive electrospray(OF-iESI)mass spectrometry platform for real-time and in-situ photoreaction monitoring.Coaxial irradiation from back of nanoelectrospray emitter with a taper section was utilized,so the emitter could act as optical lens to help achieving much larger optical power density at emitter tip compared to other sections,which allowed for in-situ reaction monitoring of photoreactions.Through theoretical calculations,the highest optical power density region volume was ca.45 nL.We also integrated a controller for the laser source(450 nm),enabling the modulation of pulse duration(>1 ms).This facilitates the study of photochemical reaction kinetics.The in-situ capability of this device was proved by capturing the short-lived photogenerated intermediates during the dehydrogenation of tetrahydroquinoline.This device was further used to investigate the kinetics of triplet energy transfer based Paternò-Büchi reaction.The reaction order has hitherto remained undetermined while the result of OF-iESI suggested it followed pseudo-second-order reaction kinetics.The short-lived donor-acceptor collision complex intermediate was also successfully identified by tandem mass spectrometry.
文摘Reman spectroscopy is used as a tool to monitor the reaction between N,N'-di(pmethyl)monothioxamides and 1,3-diamine trimethylene and to detect the reaction intermediate. By observing changes of 1024 cm^(-1) C=S band and appearance of a new bend at around 1720 cm^(-1), the reaction mechanism is discussed.
文摘Electrochemical CO2 reduction is a promising strategy for the utilization of CO2 and intermittent excess electricity.Cu is the only single metal catalyst that can electrochemically convert CO2 into multicarbon products.However,Cu exhibits an unfavorable activity and selectivity for the generation of C2 products because of the insufficient amount of CO*provided for the C‐C coupling.Based on the strong CO2 adsorption and ultrafast reaction kinetics of CO*formation on Pd,an intimate CuPd(100)interface was designed to lower the intermediate reaction barriers and improve the efficiency of C2 product formation.Density functional theory(DFT)calculations showed that the CuPd(100)interface enhanced the CO2 adsorption and decreased the CO2*hydrogenation energy barrier,which was beneficial for the C‐C coupling.The potential‐determining step(PDS)barrier of CO2 to C2 products on the CuPd(100)interface was 0.61 eV,which was lower than that on Cu(100)(0.72 eV).Encouraged by the DFT calculation results,the CuPd(100)interface catalyst was prepared by a facile chemical solution method and characterized by transmission electron microscopy.CO2 temperature‐programmed desorption and gas sensor experiments further confirmed the enhancement of the CO2 adsorption and CO2*hydrogenation ability of the CuPd(100)interface catalyst.Specifically,the obtained CuPd(100)interface catalyst exhibited a C2 Faradaic efficiency of 50.3%±1.2%at‒1.4 VRHE in 0.1 M KHCO3,which was 2.1 times higher than that of the Cu catalyst(23.6%±1.5%).This study provides the basis for the rational design of Cu‐based electrocatalysts for the generation of multicarbon products by fine‐tuning the intermediate reaction barriers.
基金the National Key Research and Development Program of China(No.2022YFB4102000)the National Natural Science Foundation of China(Nos.22102018 and 52171201)+5 种基金the Huzhou Science and Technology Bureau(No.2022GZ45)the China Postdoctoral Science Foundation-Funded Project(No.2022M710601)the Huzhou Science and Technology Bureau(No.2023GZ02)the Natural Science Foundation of Sichuan Province(No.24NSFSC5779)the National Natural Science Foundation of China(Nos.22322201 and 22278067)the Natural Science Foundation of Sichuan Province(No.2023NSFSC0094)。
文摘As an emergent energy carrier,ammonia benefits from a well-established industrial infrastructure for its transportation and production,positioning it as a promising candidate toward a carbon-free energy landscape.Within this context,the electrocatalytic ammonia oxidation reaction(AOR)is pivotal.Platinum(Pt),recognized as the most efficient AOR catalyst,has undergone extensive development over the years,yielding notable advancements across various domains,ranging from elucidating the reaction mechanism to exploring innovative materials.This review begins by elucidating the mechanism of ammonia oxidation,summarizing the evolution of the mechanism and the diverse intermediates identified through various detection methods.Subsequently,it outlines the research progress surrounding different Pt-based catalysts,followed by a discussion on standard protocols for electrochemical ammonia oxidation testing,which facilitates meaningful comparisons across studies and catalyzes the development of more efficient and potent catalysts.Moreover,the review addresses current challenges in ammonia oxidation and outlines potential future directions,providing a comprehensive outlook on the field.
基金sponsored by the National Key Research and Development Program(2021YFE0109800)the National Natural Science Foundation of China(52076126)+1 种基金the Science and Technology Committee of Shanghai Municipality(22010501500)the Key Laboratory of Clean Power Generation and Environmental Protection Technology in Mechanical Industry.
文摘Heterostructure construction has become increasingly recognized as an effective strategy to enhance oxygen evolution reaction(OER)performance due to the exposed active surfaces and improved mass/charge transfer.Inspired by natural plant structures,this study develops a unique moss-like amorphous/crystalline(CoB/CeO_(2))heterojunction.This distinctive moss-like morphology facilitates the formation of staggered sheet structures in the catalyst,providing more active sites and open channels for reaction intermediates and gas release.Benefiting from the hydrophilic properties offered by the moss-like morphology,CoB/CeO_(2) exhibits excellent OER catalytic performance in 1 M KOH,requiring only 247 mV at 100 mA cm^(-2).Physicochemical characterization and mechanistic studies reveal that the close nanoscale features between CoB and CeO_(2) create abundant binary interfaces,optimize the electronic configuration,induce changes in electronic states,and provide abundant defect sites,thereby enhancing charge transfer capabilities.This work presents a new paradigm for the design of efficient and durable OER electrocatalysts.
基金supported by the Strategic Priority Research Program of CAS(No.XDB01020300)NSF China Grants(Nos.21577149,21477139,21237005 and 21321004)NIH Grants(Nos.ES11497,RR01008 and ES00210)
文摘The ubiquitous distribution of halogenated aromatic compounds（XAr） coupled with their carcinogenicity has raised public concerns on their potential risks to both human health and the ecosystem. Recently, advanced oxidation processes（AOPs） have been considered as an＂environmentally-friendly＂ technology for the remediation and destruction of such recalcitrant and highly toxic XAr. During our study on the mechanism of metal-independent production of hydroxyl radicals（UOH） by halogenated quinones and H_2O_2, we found, unexpectedly, that an unprecedented UOH-dependent two-step intrinsic chemiluminescene（CL） can be produced by H_2O_2 and tetrachloro-p-benzoquinone, the major carcinogenic metabolite of the widely used wood preservative pentachlorophenol. Further investigations showed that, in all UOH-generating systems, CL can also be produced not only by pentachlorophenol and all other halogenated phenols, but also by all XAr tested. A systematic structure–activity relationship study for all 19 chlorophenolic congeners showed that the CL increased with an increasing number of Cl-substitution in general. More importantly, a relatively good correlation was observed between the formation of quinoid/semiquinone radical intermediates and CL generation. Based on these results, we propose that UOH-dependent formation of quinoid intermediates and electronically excited carbonyl species is responsible for this unusual CL production; and a rapid, sensitive,simple, and effective CL method was developed not only to detect and quantify trace amount of XAr, but also to provide useful information for predicting the toxicity or monitoring real-time degradation kinetics of XAr. These findings may have broad chemical, environmental and biological implications for future studies on halogenated aromatic persistent organic pollutants.
基金supported by the National Key R&D Program of China (2021YFA1501503)the National Natural Science Foundation of China (22125205,22002155,22002158,92045302)+5 种基金the“Transformational Technologies for Clean Energy and Demonstration”Strategic Priority Research Program of the Chinese Academy of Sciences (XDA21070613)the Fundamental Research Funds for the Central Universities (20720220008)the China Postdoctoral Science Foundation (2019M661142)the Natural Science Foundation of Liaoning Province (2021-MS-022)the High-Level Talents Innovation Project of Dalian City (2020RQ038)the support from the Photon Science Center for Carbon Neutrality。
文摘Simultaneously achieving high activity,selectivity and stability for electrochemical CO_(2)reduction reaction(CO_(2)RR)remains great challenges.Herein,a phosphorus-modified Sn/Sn Oxcore/shell(P-Sn/SnO_x)catalyst,derived from in situ electrochemical reduction of an amorphous Sn(HPO_(4))_(2) pre-catalyst,exhibits high CO_(2)RR performance.The total Faradaic efficiency(FE)of C_(1) products is close to 100%in a broad potential range from-0.49 to-1.02 V vs.reversible hydrogen electrode,and a total current density of 315.0 m A cm^(-2)is achieved.Moreover,the P-Sn/SnO_(x) catalyst maintains a formate FE of~90%for 120 h.Density functional theory calculations suggest that the phosphorus-modified Sn/SnO_(x) core/shell structure effectively facilitates formate production by enhancing CO_(2)adsorption and improving free energy profile of formate formation.
文摘he initiation mechanism of ceric ion/2-benzoyl acetanilide system was studiedby means of FT-IR, EPR and kinetic studies which revealed that 2-benzoyl ac-etanilide acts as a very active promotor to the polymerization initiated by ceric ion.The initiation mechanism was then proposed which involved the complex formationbetween a ceric ion and a l ,3-diketone group or a carbamate group, followed by,thedecomposition of the complex to generate C-centered secondary alkyl radical and N-centered anillido radical, both of which would initiate polymerization of vinylmonomer as the end groups of the polymers formed.
文摘The production of valuable chemicals using copper(Cu)catalysts via electrochemical CO or CO_(2)reduction reactions(CORR and CO_(2)RR)has shown great potential in the field of sustainable energy conversion[1].Previous research has primarily focused on analyzing the behavior of reaction intermediates or solely on the dynamics within the solution phase,while the synergistic effects between surface species and the solution,particularly the interfacial water and its non-covalent interactions with the Cu surface,have remained partially understood[2].
文摘Though ammonia borane NH_(3)BH_(3)(AB)was discovered in the 1950s,it is fair to state that AB as a potential chemical hydrogen storage material was discovered more recently,in the 2000s.Unlike the isoelectronic ethane CH_(3)CH_(3),AB is polar;three of its hydrogens are protic(NH_(3)group)and the other three are hydridic(BH_(3)group);the material is solid at ambient conditions owing to dihydrogen N–H^(δ+)…H^(δ−)–B interactions;and AB decomposes from 90℃under thermogravimetric conditions.With such properties,AB has attracted much attention,even though AB in neat form is not suitable for the application mentioned above because it decomposes more than it dehydrogenates.Hence,strategies(based on solubilization,catalysis,chemical doping and nanosizing)aiming at destabilizing AB to make it release pure H_(2)at<100℃have been developed.Beyond the performance targeted for hydrogen storage,this provided us with better understanding of the mechanisms of decomposition.Indeed,studies on thermal decomposition of neat AB have revealed just how complex the mechanisms are(due to the involvement of two possible key intermediates initiating the decomposition,the formation of various volatile products,the existence of counterintuitive homopolar reactions,and the formation of polymeric residues of complex composition,for example).Studies on destabilized AB have provided insights into several mechanistic aspects including the reaction intermediates,the decomposition pathways,and the nature of the residue forming upon the release of 1 and≥2 equiv.H_(2).We presently have a fairly good understanding of the mechanisms of decomposition of AB,which is discussed in more detail below.In that respect,this review focuses firstly on the complexity of thermal decomposition of neat AB,secondly on what we know with regard to thermal decomposition of destabilized AB,and thirdly on all outstanding questions.It is very important to have an excellent knowledge of the reaction mechanisms if technological progress is to be made with AB as a chemical hydrogen storage material.
基金the Natural Science Foundation of Shandong Province(ZR2020QB068)China Postdoctoal Science Foundation(2021M691701).
文摘Elaborate interface engineering based on in situ surface reconstruction during catalysis,especially at the cathode,is effective at promoting the hydrogen evolution reaction(HER)but is plagued by the uncontrollable extent of the reconstruction and structure collapse.In view of the reasonable adsorption of reaction intermediates and accelerating kinetics of hydroxy oxides(MOOH),we focused on the in situ structural evolution of the HER electrode toward MOOH during catalysis,which has been revealed by operando Raman spectroscopy yet seldom reported.As a typical example,Mn-doped NiS_(2)was selected as the HER electrode to monitor in situ structural evolution toward hydroxy oxides(cathode in situ-derived NiOOH,CISD-NiOOH)as Mn-NiS_(2)@CISD-NiOOH coupling catalysts.In situ formation of MOOH on the cathode is interesting.Moreover,the existence of Mn dopants renders Mn-NiS_(2)with lattice distortion and a rough surface consisting of nanoparticles of∼25 nm in diameter,differing from the smooth NiS_(2).In 1 M KOH,Mn-NiS_(2)@CISD-NiOOH exhibits a low overpotential of 330 mV to deliver 1000 mA cm^(−2)and an excellent stability of 100 h at 1300 mA cm^(−2).Notably,in alkaline seawater(1 M KOH+seawater)as well as 30%KOH industrial electrolyte,it still exhibits stable HER operation above 1000 mA cm^(−2)for at least 100 h.This study not only expands the prospects for in situ cathode structure development but also offers a robust catalytic cathode with high activity for industrial hydrogen-production systems.
文摘The efficiency of CO_(2) photoreduction is significantly constrained by uncontrollable reaction intermediates as well as the weak adsorption and tough activation of CO_(2).Herein,we report a surface modulation strategy via hydroxyl (–OH) modification to tune the surface state of oxygen-rich-vacancy SrTiO_(3)(STO),which could efficiently optimize the structural attributes of STO,facilitating the robust generation of intermediate COOH^(*) and enhancing the surface affinity of the catalyst for CO_(2) adsorption and activation.Therefore,the CO evolution rate of the STO-OH-5 (90 μmol g^(−1)h^(−1)) catalyst is 2.6 times higher than that of the original STO (34 μmol g^(−1)h^(−1)),outperforming most other reported photocatalysts.This study elucidates the impact of surface modulation on the photocatalytic performance of STO and presents a viable strategy for the development of high-performance nanomaterial photocatalysts for CO_(2) conversion.
基金Supported by the National Natural Science Foundation of China(12275186,11705242,12175156,11805138,11905120)the Fundamental Research Funds For the Central Universities in China(YJ201954,YJ201820)。
文摘In this article,we investigate the dependence of nuclear temperature on emitting source neutron-proton(N/Z)asymmetry with light charged particles(LCPs)and intermediate mass fragments(IMFs)generated from intermediate-velocity sources in thirteen reaction systems with different N/Z asymmetries,^(64)Zn on^(112)Sn,and^(70)Zn,^(64)Ni on^(112,124)Sn,^(58,64)Ni,^(197)Au,and^(232)Th at 40 MeV/nucleon.The apparent temperature values of LCPs and IMFs from different systems are deduced from the measured yields using two helium-related and eight carbon-related double isotope ratio thermometers,respectively.Then,the sequential decay effect on the experimental apparent temperature deduction with the double isotope ratio thermometers is quantitatively corrected explicitly with the aid of the quantum statistical model.The present treatment is an improvement compared to our previous studies in which an indirect method was adopted to qualitatively consider the sequential decay effect.A negligible N/Z asymmetry dependence of the real temperature after the correction is quantitatively addressed in heavy-ion reactions at the present intermediate energy,where a change of o.1 units in source N/Z asymmetry corresponds to an absolute change in temperature of an order of 0.03 to 0.29 MeV on average for LCPs and IMFs.This conclusion is in close agreement with that inferred qualitatively via the indirect method in our previous studies.
