The quest for sustainable energy solutions has intensified the search for alternative feedstocks that can supplement or replace fossil fuels. Obtaining fuels or chemicals through the conversion of renewable biomass is...The quest for sustainable energy solutions has intensified the search for alternative feedstocks that can supplement or replace fossil fuels. Obtaining fuels or chemicals through the conversion of renewable biomass is a promising candidate [1,2]. Some noblemetal-based (e.g., Pt, Pd and Rh) catalysts exhibit significant catalytic activity to the conversion reaction of these biomass.展开更多
In-situ conversion of subsurface hydrocarbons via electromagnetic(EM)heating has emerged as a promising technology for producing carbon-zero and affordable hydrogen(H_(2))directly from natural gas reservoirs.However,t...In-situ conversion of subsurface hydrocarbons via electromagnetic(EM)heating has emerged as a promising technology for producing carbon-zero and affordable hydrogen(H_(2))directly from natural gas reservoirs.However,the reaction pathways and role of water as an additional hydrogen donor in EM-assisted methane-to-hydrogen(CH_(4)-to-H_(2))conversion are poorly understood.Herein,we employ a combination of lab-scale EM-heating experiments and reaction modeling analyses to unravel reaction pathways and elucidate water's role in enhancing hydrogen production.The labelled hydrogen isotope of deuterium oxide(D_(2)O)is used to trace the sources of hydrogen.The results show that water significantly boosts hydrogen yield via coke gasification at around 400℃and steam methane reforming(SMR)reaction at over 600℃in the presence of sandstone.Water-gas shift reaction exhibits a minor impact on this enhancement.Reaction mechanism analyses reveal that the involvement of water can initiate auto-catalytic loop reactions with methane,which not only generates extra hydrogen but also produces OH radicals that enhance the reactants'reactivity.This work provides crucial insights into the reaction mechanisms involved in water-carbon-methane interactions and underscores water's potential as a hydrogen donor for in-situ hydrogen production from natural gas reservoirs.It also addresses the challenges related to carbon deposition and in-situ catalyst regeneration during EM heating,thus derisking this technology and laying a foundation for future pilots.展开更多
Conversion electrodes typically have high theoretical specific capacity,but mostly suffer large structural changes during charge/discharge and result in poor cycling stability.The optimization of the polycrystalline m...Conversion electrodes typically have high theoretical specific capacity,but mostly suffer large structural changes during charge/discharge and result in poor cycling stability.The optimization of the polycrystalline materials is the mostly used strategy,however,these polycrystalline materials are intrinsically vulnerable to grain-boundary(intergranular)fracture caused by the anisotropic volume change during sodiation/desodiation,resulting in rapid impedance growth and capacity decay.Herein,we propose an alternative pathway to design single-crystal materials as potential conversion anodes.As an example,SnO_(2)with different crystallinities is successfully synthesized via solvothermal methods and compared to determine the implications of different crystallinity for the electrochemical properties of conversion anodes.It is demonstrated that the single-crystal SnO_(2)not only has faster Na+diffusion dynamics but also maintains structural stability via topotactic reaction.Further optimization of the electron conduction and structural robustness is realized by uniformly covering a graphitic carbon shell on the surface of single-crystal SnO_(2)nanosheets.The modified singlecrystal SnO_(2)exhibits a high reversible capacity of 436.2 mA h g^(-1)and maintains a high capacity of 257.1 mA h g−1 and remarkable capacity retention of about 98.9%after 9000 cycles at 5000 mA g−1.The deep understandings of the topotactic reaction in single crystal conversion anode in this work provide a theoretical foundation and new direction for further developing electrode materials with excellent electrochemical performance,especially high rate capabilities,and long cyclability.展开更多
Methane, an abundant one-carbon(C_(1)) resource, is extensively used in the industrial production of vital fuels and value-added chemicals. However, current industrial methane conversion technologies are energy-and ca...Methane, an abundant one-carbon(C_(1)) resource, is extensively used in the industrial production of vital fuels and value-added chemicals. However, current industrial methane conversion technologies are energy-and carbon-intensive, mainly due to the high activation energy required to break the inert C–H bond, low selectivity, and problematic side reactions, including CO_(2)emissions and coke deposition. Electrochemical conversion of methane(ECM) using intermittent renewable energy offers an attractive solution, due to its modular reactor design and operational flexibility across a broad spectrum of temperatures and pressures. This review emphasizes conversion pathways of methane in various reaction systems, highlighting the significance and advantages of ECM in facilitating a sustainable artificial carbon cycle. This work provides a comprehensive overview of conventional methane activation mechanisms and delineates the complete pathways of methane conversion in electrolysis contexts. Based on surface/interface chemistry, this work systematically analyzes proposed reaction pathways and corresponding strategies to enhance ECM efficiency towards various target products, including syngas, hydrocarbons, oxygenates, and advanced carbon materials. The discussion also encompasses opportunities and challenges for the ECM process, including insights into ECM pathways, rational electrocatalyst design, establishment of benchmarking protocols, electrolyte engineering, enhancement of CH4conversion rates, and minimization of CO_(2)emission.展开更多
Exploring efficient transition-metal-based electrocatalysts is critical for the wide application of electrochemical hydrogen generation technology.Although the phase displays prominent influence on their performance,i...Exploring efficient transition-metal-based electrocatalysts is critical for the wide application of electrochemical hydrogen generation technology.Although the phase displays prominent influence on their performance,it remains a major challenge to achieve phase regulation in the same synthesis method and elucidate the intrinsic relationship between the phase and activity.Herein,we developed a sulfur induced electrodeposition strategy to achieve the precise phase regulation of nickel-based materials from Ni(OH)_(2)to Ni and Ni_(3)S_(2).S atoms can be introduced into Ni and Ni(OH)_(2)due to sulfur inducement,and the S proportion is finely controlled via changing the deposition parameters.Importantly,the obtained S-Ni catalyst displays enhanced hydrogen evolution activity with an ultralow overpotential of 27 mV at 10 mA cm^(-2),which is superior to the S-Ni(OH)_(2),Ni_(3)S_(2),and even Pt/C.Density functional theory(DFT)calculations disclose the S-Ni catalyst exhibits optimal charge state and local coordination,remarkably optimizing the water adsorption and Ni-H^(*)binding energy.This work provides new insights into phase regulation in electrodeposition and an understanding of the intrinsic relationship between phase and activity.展开更多
Lithium-sulfur(Li-S)batteries are considered a potential candidate for next-generation energy-dense and sustainable energy storage.However,the slow conversion and severe shuttle of polysulfides(LiPSs)result in rapid p...Lithium-sulfur(Li-S)batteries are considered a potential candidate for next-generation energy-dense and sustainable energy storage.However,the slow conversion and severe shuttle of polysulfides(LiPSs)result in rapid performance degradation over long-term cycling.Herein,we report a high-entropy single-atom(HE-SA)catalyst to regulate the multi-step conversion of LiPS to attain a high-performance Li-S battery.Both the density functional theory calculations and the experimental results prove that the Fe atomic site with high spin configurations strongly interacts with Li_(2)S_(4)through d-p and s-p synergistic orbital hybridization which facilitates the reduction of LiPS.Moreover,S-dominant p-d hybridization between Li_(2)S and a high-spin Mn site weakens the Li-S bond and facilitates the rapid sulfur evolution reaction.Consequently,the Li-S battery with a bifunctional HE-SA catalyst shows an ultralow capacity decay of 0.026% per cycle over 1900 cycles at 1 C.This work proposes a high-entropy strategy for sculpting electronic structures to enable spin and orbital hybridization modulation in advanced catalysts toward longcycling Li-S batteries.展开更多
We present the performance of a post-plasma carbon bed for improving plasma-based CO_(2)conversion,studying the effect of bed length and additional thermal bed insulation.The experiments were conducted using an atmosp...We present the performance of a post-plasma carbon bed for improving plasma-based CO_(2)conversion,studying the effect of bed length and additional thermal bed insulation.The experiments were conducted using an atmospheric pressure gliding arc plasmatron in both high and low specific energy input(SEI)regimes.Each bed was equipped with a silo to enable continuous carbon feeding and operation for an order of 1 h,thus overcoming previous limitations in literature.Importantly,we derive an improved energy efficiency(EE)calculation with an accurate and unambiguous consideration of the key reaction contributions of both plasma and carbon bed.This derivation serves to highlight the inconsistencies that arise in determining EE in such a complex chemical system.We therefore advise and advocate for the use of energy cost(EC)as the key reported energy metric in systems using post-plasma carbon beds.The optimum conversion and energy metrics were obtained with the longest bed,reaching a conversion of 41%,an EE of 51%and an EC of 0.41 MJ/mol at high SEI.The design of the insulated bed and silo allow for previously unreported preheating of the carbon,which reduces oscillations observed in the conversion profiles of the short and long beds.Preheating of the external silo for the long bed also yields a near-complete removal of oscillations.Finally,when comparing our performance with results from literature for postplasma carbon beds,our system clearly improves upon the state-of-the-art,both in absolute values of conversion and energy metrics at the same SEI,as well as by sustaining this improvement for extended periods of time.展开更多
Conversion of CO2 into CO using plasma processing powered by renewable energy is a promising method to convert intermittent sustainable electricity into storable chemical energy.Despite extensive research efforts worl...Conversion of CO2 into CO using plasma processing powered by renewable energy is a promising method to convert intermittent sustainable electricity into storable chemical energy.Despite extensive research efforts worldwide,there is currently no process that achieves economically viable values for both CO2 conversion fraction and energy recovery efficiency simultaneously.Here we demonstrate that a process that utilizes the Boudouard reaction,CO^2++C→2 CO,driven by a thermal plasma allows both 95%CO2 conversion to CO and energy recovery efficiency of 70%,values far higher than seen so far.By comparing the conversion process with and without CO2 excitation by a plasma and by using optical emission spectroscopy we show that the improved performance is due to a novel mode of operation where CO2 is pyrolyzed into an active mixture of CO,O and O2 by an arc discharge which is then introduced into a fixed bed to interact with carbon material.In this way,the free oxygen in the mixture combusts with carbon to form CO,and residual plasma excited CO2 is reduced by carbon.In the overall process,the endothermic Boudouard reaction is partially replaced by an exothermic reaction,and the excess electric energy to produce CO2 plasma is reused in the carbon bed.展开更多
Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electroch...Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electrochemical properties. The CoMn204 anode can deliver a large capacity of 1070 mAh g-1 in thefirst discharge, a reversible capacity of 500 mAh g^-1 after 100 cycles with a coulombic efficiency of 98.5% at a charge-discharge current density of 200 mA g^-l, and a specific capacity of 385 mAh g^-1 at a muchhigher charge-discharge current density of 1600mA g^-1. Synchrotron X-ray absorption fine structure（XAFS） techniques were applied to investigate the conversion reaction mechanism of the CoMn204 anode.The X-ray absorption near edge structure （XANES） spectra revealed that, in the first discharge-charge cy-cle, Co and Mn in CoMn204 were reduced to metallic Co and Mn when the electrode was discharged to0.01 V, while they were oxidized respectively to CoO and MnO when the electrode was charged to 3.0V.Experiments of both XANE5 and extended X-ray absorption fine structure （EXAFS） revealed that neithervalence evolution nor phase transition of the porous core-shell CoMn204 microspheres could happen inthe discharge plateau from 0.8 to 0.6V, which demonstrates the formation of solid electrolyte interface（SEI） on the anode.展开更多
Molybdenum carbides are highly active for CO2 conversion to CO via the reverse water-gas shift(RWGS)reaction, however the large grain size up to micrometers renders its relatively lower active sites utilization effici...Molybdenum carbides are highly active for CO2 conversion to CO via the reverse water-gas shift(RWGS)reaction, however the large grain size up to micrometers renders its relatively lower active sites utilization efficiency while generating CH4 as a by-product. In this work, a homogeneously dispersed molybdenum carbide hybrid catalyst with sub-nanosized cluster(the average size as small as 0.5 nm) is prepared via a facile carbothermal treatment for highly selective CO2-CO reduction. The partially disordered Mo2C clusters are characterized by synchrotron high-resolution XRD and atomic resolution HAADF-STEM analysis, for which the source cause of the disorder is pinpointed by XAFS analysis to be the nitrogen intercalants from the carbonaceous precursor. The partially disordered Mo2C clusters show a RWGS rate as high as 184.4 μmol gMo2C-1s-1 at 400 ℃ with a superior selectivity toward CO(> 99.5%). This work 2 highlights a facile strategy for fabricating highly dispersed and partially disordered Mo2C clusters at a sub-nano size with beneficial N-doping for delivering high catalytic activity and operational stability.展开更多
The deep-processing utility of pure hydrogen sulfide (H_(2)S) is a significant direction in natural gas chemical industry.Herein,a brand-new strategy of H_(2)S conversion by a,β-unsaturated carboxylate esters into th...The deep-processing utility of pure hydrogen sulfide (H_(2)S) is a significant direction in natural gas chemical industry.Herein,a brand-new strategy of H_(2)S conversion by a,β-unsaturated carboxylate esters into thiols or thioethers using task-specific carboxylate ionic liquids (ILs) as catalyst has been developed,firstly accomplishing the phase separation of product and catalyst without introducing the third component.It can be considered as a cascade reaction in which the product selectivity can be controlled by adjusting the molar ratio of H_(2)S to a,β-unsaturated carboxylate esters.Also,the effects of ILs with different anions and cations,intermittent feeding operations,as well as pressure-time kinetic behaviors on cascade reaction were investigated.Furthermore,the proposed interaction mechanism of H_(2)S conversion using butyl acrylate catalyzed by[Emim][Ac]was revealed by DFT-based theoretical calculation.The approach enables the self-phase separation promotion of catalyst and product and achieves 99%quantitative conversion under mild conditions in the absence of solvent,making the entire process ecologically benign.High-efficiency reaction activity can still be maintained after ten cycles of the catalyst.Therefore,the good results,combined with its simplicity of operation and the high recyclability of the catalyst,make this green method environmentally friendly and cost-effective.It is anticipated that this self-separation method mediated by task-specific ILs will provide a feasible strategy for H_(2)S utilization,which will guide its application on an industrial scale.展开更多
The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 t...The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.展开更多
The reaction mechanism of zeolite- or zeotype-catalyzed methanol-to-olefins（MTO） conversion is still a subject of debate. Employing periodic density functional theory calculations, the olefin-based cycle was studied...The reaction mechanism of zeolite- or zeotype-catalyzed methanol-to-olefins（MTO） conversion is still a subject of debate. Employing periodic density functional theory calculations, the olefin-based cycle was studied using tetramethylethene（TME） as a representative olefinic hydrocarbon pool in H-SAPO-18 zeotype. The overall free energy barrier at 673 K was calculated and found to be less than 150 kJ/mol in the TME-based cycle, much lower than those in the aromatic-based cycle（〉 200 kJ/mol）, indicating that olefins themselves are the dominant active hydrocarbon pool species in H-SAPO-18. The similarity of the intermediates involved between the aromatic-based cycle and the olefin-based cycle was also highlighted, revealing that both cycles were pattern-consistent. The selectivity related to the distribution of cracking precursors, such as higher olefins or carbenium ions, as a result of the olefin-based cycle for the MTO conversion. The enthalpy barrier of the crack-ing step scaled linearly with the number of carbon atoms of cracking precursors to produce ethene or propene with ethene being much less favored than propene for cracking of C7 and higher pre-cursors. This work highlighted the importance of the olefin-based cycle in H-SAPO-18 for the MTO conversion and established the similarity between the olefin-based and aromatic-based cycles.展开更多
MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years...MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years.Herein,we report the intriguing light-to-heat conversion property of vanadium carbide(V_(2)C)MXene under irradiation of millisecond laser pulse.Unlike the typical photothermal materials,the V_(2)C MXene not only converts the incident laser energy to heat by the physical photothermal effect,but also triggers the exothermic oxidation of the V_(2)C MXene.The oxidation could be greatly promoted with addition of plasmonic Au nanorods(Au NRs)for light absorption enhancement.Owing to the unique light-to-heat conversion property,the Au NRs/V_(2)C MXene membrane could serve as high temperature pulse(HTP)generators that is proposed for numerous applications with high demand for immediacy.As a proof-of concept application,Au NRs/V_(2)C MXene membrane was applied for laser ignition of the high energy density materials,such as 2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane(HNIW or CL-20).An improved ignition performance,in terms of lowered laser threshold,is achieved as compared to the state-of-the-art light-to-heat conversion materials.展开更多
Efforts have been made to develop a promising anode material with a novel composition for sodiumion batteries(SIBs).In this study,the sodium-ion storage mechanism of transition metal selenite that comprises transition...Efforts have been made to develop a promising anode material with a novel composition for sodiumion batteries(SIBs).In this study,the sodium-ion storage mechanism of transition metal selenite that comprises transition metal cation coupled with two anions is studied.Amorphous cobalt selenite(CoSeO_(3))-carbon composite nanofibers containing numerous pores are synthesized via electrospinning process.Upon heat treatment of the electrospun nanofibers containing selenium,CoSe_(2)nanoclusters are formed.During the subsequent oxidation,CoSe_(2)transformed into amorphous CoSeO_(3)and some part of carbon was oxidized into CO_(2),leaving the pores inside the nanofiber.To unveil the electrochemical reaction mechanism,analytical methods including cyclic voltammetry,ex-situ X-ray photoelectron spectroscopy,ex-situ transmission electron microscopy,and in-situ electrochemical impedance spectroscopy techniques were adopted.Based on the analyses,the following conversion reaction from the second cycle onward is suggested:CoO+xSeO_(2)+(1-x)Se+4(x+1)Na^(+)+4(x+1)e~-?Co+(2x+1)Na_(2)O+Na_(2)Se.Furthermore,the electrochemical properties of porous CoSeO_(3)-carbon composite nanofibers are analyzed in detail.The anode material exhibited stable cycle stability up to 200 cycles at 0.5 A g^(-1)and high rate performance up to 5 A g^(-1).展开更多
Developing highly active and robust oxygen evolution reaction(OER)electrocatalysts is still a critical challenge for water electrolyzers and metal-air batteries.Realizing the dynamic evolution of the intermediate and ...Developing highly active and robust oxygen evolution reaction(OER)electrocatalysts is still a critical challenge for water electrolyzers and metal-air batteries.Realizing the dynamic evolution of the intermediate and charge transfer during OER and developing a clear OER mechanism is crucial to design high-performance OER catalysts.Recently in Nature,Xue and colleagues revealed a new OER mechanism,coupled oxygen evolution mechanism(COM),which involves a switchable metal and oxygen redox under light irradiation in nickel oxyhydroxide-based materials.This newly developed mechanism requires a reversible geometric conversion between octahedron(NiO_(6))and square planar(NiO_(4))to achieve electronic states with both“metal redox”and“oxygen redox”during OER.The asymmetric structure endows NR-NiOOH with a nonoverlapping region between the dz^(2) orbitals and a_(1g)^(*)bands,which facilitate the geometric conversion and enact the COM pathway.As a result,NR-NiOOH exhibited better OER activity and stability than the traditional NiOOH.展开更多
Nanostructured materials have received tremendous interest due to their unique mechanical/electrical properties and overall behavior contributed by the complex synergy of bulk and interfacial properties for efficient ...Nanostructured materials have received tremendous interest due to their unique mechanical/electrical properties and overall behavior contributed by the complex synergy of bulk and interfacial properties for efficient and effective energy conversion and storage. The booming development of nanotechnology affords emerging but effective tools in designing advanced energy material. We reviewed the significant progress and dominated nanostructured energy materials in electrochemical energy conversion and storage devices, including lithium ion batteries, lithium-sulfur batteries, lithium-oxygen batteries, lithium metal batteries, and supercapacitors. The use of nanostructured electrocatalyst for effective electrocatalysis in oxygen reduction and oxygen evolution reactions for fuel cells and metal-air batteries was also included. The challenges in the undesirable side reactions between electrolytes and electrode due to high electrode/electrolyte contact area, low volumetric energy density of electrode owing to low tap density, and uniform production of complex energy materials in working devices should be overcome to fully demonstrate the advanced energy nanostructures for electrochemical energy conversion and storage. The energy chemistry at the interfaces of nanostructured electrode/electrolyte is highly expected to guide the rational design and full demonstration of energy materials in a working device. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.展开更多
Ethanol conversion to high-value-added products has attracted considerable attention in both academic research and industrial fields.In this study,we synthesized a series of tunable acid–base bifunctional Zn-Zr-Al me...Ethanol conversion to high-value-added products has attracted considerable attention in both academic research and industrial fields.In this study,we synthesized a series of tunable acid–base bifunctional Zn-Zr-Al metal oxides(represented as Zn2ZrxAl-MMO)in light of the structural topotactic transformation of Zn2ZrxAl-hydrotalcite precursors(Zn2ZrxAl-LDH).The resulting Zn2ZrxAl-MMO catalysts were employed in the conversion of ethanol to diethyl carbonate.The Zr^4+ ion content of the LDH precursor plays a key role in modulating the acid-base properties and determining catalytic performance:the Zn2Zr0.1Al-MMO sample exhibits the optimal catalytic behavior with a diethyl carbonate(DEC)yield of 42.1%,which is the highest reported for metal oxide catalysts.Structure-property correlation investigations revealed that the synergic catalysis between medium-strong basic sites and weak acid sites plays a predominant role in the catalytic behavior.Furthermore,in situ Fourier transform infrared measurements showed that the weak acidic site promotes activation adsorption of the reactant(urea)and the intermediate product(ethyl carbamate),while the medium-strong basic site accelerates ethanol activation.Moreover,the Zn2Zr0.1Al-MMO catalyst has the advantages of cost effectiveness,good stability,and reusability.Therefore,the acid-base bifunctional catalysts developed in this work can be employed as promising candidates in acid-base catalytic reactions such as ethanol conversion.展开更多
Plasma methane (CH_4) conversion in gliding arc discharge was examined. Theresult data of experiments regarding the performance of gliding arc discharge were presented in thispaper. A simulation which is consisted som...Plasma methane (CH_4) conversion in gliding arc discharge was examined. Theresult data of experiments regarding the performance of gliding arc discharge were presented in thispaper. A simulation which is consisted some chemical kinetic mechanisms has been provided toanalyze and describe the plasma process. The effect of total gas flow rate and input frequencyrefers to power consumption have been studied to evaluate the performance of gliding arc plasmasystem and the reaction mechanism of decomposition. Experiment results indicated that the maximumconversion of CH_4 reached 50% at the total gas flow rate of 1 L/min. The plasma reaction wasoccurred at the atmospheric pressure and the main products were C (solid), hydrogen, and acetylene(C_2H_2). The plasma reaction of methane conversion was exothermic reaction which increased theproduct stream temperature around 30-50℃.展开更多
Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and ...Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and pseudomorphic conversion to SrC2 O4·H2O occurs. In the second step, SrC2 O4·H2O reacts with H2C2O4 to form H[Sr(C2 O4)1.5(H2O)]. Sr(HC2 O4)(C2 O4)0.5·H2 O crystallizes during cooling of the reaction mixture to room temperature if the solution reaches the saturation concentration of (H[Sr(C2O4)1.5(H2O)]. The aims of this study are the derivation of reaction rate equations and the determination of the kinetic parameters such as pre-exponential factor, apparent activation energy and order of H2C2O4 concentration for each reaction step.Fractional conversions of SrSO4 were calculated using the quantitative amounts of dissolved S and Sr. It was determined that the reaction rate increased at the initial time of reaction by increasing the temperature using solutions with approximately same H2C2O4 concentrations. The reaction extends very slowly after a certain time in solutions with low H2C2O4 concentration and ends by the formation of a protective layer of SrC2O4-H2O around the surfaces of solid particles. Fractional conversion of SrSO4 is increased by increasing concentration of H2C2O4 at constant temperature. Kinetic model equations were derived using shrinking core model for each step.展开更多
文摘The quest for sustainable energy solutions has intensified the search for alternative feedstocks that can supplement or replace fossil fuels. Obtaining fuels or chemicals through the conversion of renewable biomass is a promising candidate [1,2]. Some noblemetal-based (e.g., Pt, Pd and Rh) catalysts exhibit significant catalytic activity to the conversion reaction of these biomass.
基金supported by a generous gift from The CH Foundationthe support from the Distinguished Graduate Student Assistantship and the Graduate Research Support Award at Texas Tech University+1 种基金the Aid fund from AAPGthe Matejek Family Faculty Fellowship。
文摘In-situ conversion of subsurface hydrocarbons via electromagnetic(EM)heating has emerged as a promising technology for producing carbon-zero and affordable hydrogen(H_(2))directly from natural gas reservoirs.However,the reaction pathways and role of water as an additional hydrogen donor in EM-assisted methane-to-hydrogen(CH_(4)-to-H_(2))conversion are poorly understood.Herein,we employ a combination of lab-scale EM-heating experiments and reaction modeling analyses to unravel reaction pathways and elucidate water's role in enhancing hydrogen production.The labelled hydrogen isotope of deuterium oxide(D_(2)O)is used to trace the sources of hydrogen.The results show that water significantly boosts hydrogen yield via coke gasification at around 400℃and steam methane reforming(SMR)reaction at over 600℃in the presence of sandstone.Water-gas shift reaction exhibits a minor impact on this enhancement.Reaction mechanism analyses reveal that the involvement of water can initiate auto-catalytic loop reactions with methane,which not only generates extra hydrogen but also produces OH radicals that enhance the reactants'reactivity.This work provides crucial insights into the reaction mechanisms involved in water-carbon-methane interactions and underscores water's potential as a hydrogen donor for in-situ hydrogen production from natural gas reservoirs.It also addresses the challenges related to carbon deposition and in-situ catalyst regeneration during EM heating,thus derisking this technology and laying a foundation for future pilots.
基金supported by the National Natural Science Foundation of China(No.51971065)the Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-07-E00028)The authors would like to thank SCI-GO(www.sci-go.com)for the XPS analysis.
文摘Conversion electrodes typically have high theoretical specific capacity,but mostly suffer large structural changes during charge/discharge and result in poor cycling stability.The optimization of the polycrystalline materials is the mostly used strategy,however,these polycrystalline materials are intrinsically vulnerable to grain-boundary(intergranular)fracture caused by the anisotropic volume change during sodiation/desodiation,resulting in rapid impedance growth and capacity decay.Herein,we propose an alternative pathway to design single-crystal materials as potential conversion anodes.As an example,SnO_(2)with different crystallinities is successfully synthesized via solvothermal methods and compared to determine the implications of different crystallinity for the electrochemical properties of conversion anodes.It is demonstrated that the single-crystal SnO_(2)not only has faster Na+diffusion dynamics but also maintains structural stability via topotactic reaction.Further optimization of the electron conduction and structural robustness is realized by uniformly covering a graphitic carbon shell on the surface of single-crystal SnO_(2)nanosheets.The modified singlecrystal SnO_(2)exhibits a high reversible capacity of 436.2 mA h g^(-1)and maintains a high capacity of 257.1 mA h g−1 and remarkable capacity retention of about 98.9%after 9000 cycles at 5000 mA g−1.The deep understandings of the topotactic reaction in single crystal conversion anode in this work provide a theoretical foundation and new direction for further developing electrode materials with excellent electrochemical performance,especially high rate capabilities,and long cyclability.
基金National Key R&D Program of China (2023YFA1508001 and 2023YFA1508002)National Natural Science Foundation of China (22272120 and U2202251)+1 种基金Hainan Province Science and Technology Special Fund(ZDYF2023SHFZ120)Research Foundation of Marine Science and Technology Collaborative Innovation Center of Hainan University (XTCX2022HYB01)。
文摘Methane, an abundant one-carbon(C_(1)) resource, is extensively used in the industrial production of vital fuels and value-added chemicals. However, current industrial methane conversion technologies are energy-and carbon-intensive, mainly due to the high activation energy required to break the inert C–H bond, low selectivity, and problematic side reactions, including CO_(2)emissions and coke deposition. Electrochemical conversion of methane(ECM) using intermittent renewable energy offers an attractive solution, due to its modular reactor design and operational flexibility across a broad spectrum of temperatures and pressures. This review emphasizes conversion pathways of methane in various reaction systems, highlighting the significance and advantages of ECM in facilitating a sustainable artificial carbon cycle. This work provides a comprehensive overview of conventional methane activation mechanisms and delineates the complete pathways of methane conversion in electrolysis contexts. Based on surface/interface chemistry, this work systematically analyzes proposed reaction pathways and corresponding strategies to enhance ECM efficiency towards various target products, including syngas, hydrocarbons, oxygenates, and advanced carbon materials. The discussion also encompasses opportunities and challenges for the ECM process, including insights into ECM pathways, rational electrocatalyst design, establishment of benchmarking protocols, electrolyte engineering, enhancement of CH4conversion rates, and minimization of CO_(2)emission.
基金supported by the National Natural Science Foundation of China(52271210,22179032,52171176)。
文摘Exploring efficient transition-metal-based electrocatalysts is critical for the wide application of electrochemical hydrogen generation technology.Although the phase displays prominent influence on their performance,it remains a major challenge to achieve phase regulation in the same synthesis method and elucidate the intrinsic relationship between the phase and activity.Herein,we developed a sulfur induced electrodeposition strategy to achieve the precise phase regulation of nickel-based materials from Ni(OH)_(2)to Ni and Ni_(3)S_(2).S atoms can be introduced into Ni and Ni(OH)_(2)due to sulfur inducement,and the S proportion is finely controlled via changing the deposition parameters.Importantly,the obtained S-Ni catalyst displays enhanced hydrogen evolution activity with an ultralow overpotential of 27 mV at 10 mA cm^(-2),which is superior to the S-Ni(OH)_(2),Ni_(3)S_(2),and even Pt/C.Density functional theory(DFT)calculations disclose the S-Ni catalyst exhibits optimal charge state and local coordination,remarkably optimizing the water adsorption and Ni-H^(*)binding energy.This work provides new insights into phase regulation in electrodeposition and an understanding of the intrinsic relationship between phase and activity.
基金supported by the National Natural Science Foundation of China(52302240)the Macao Young Scholars Program(AM2023011)the Yuanguang Scholars Program,Hebei University of Technology(282022554)。
文摘Lithium-sulfur(Li-S)batteries are considered a potential candidate for next-generation energy-dense and sustainable energy storage.However,the slow conversion and severe shuttle of polysulfides(LiPSs)result in rapid performance degradation over long-term cycling.Herein,we report a high-entropy single-atom(HE-SA)catalyst to regulate the multi-step conversion of LiPS to attain a high-performance Li-S battery.Both the density functional theory calculations and the experimental results prove that the Fe atomic site with high spin configurations strongly interacts with Li_(2)S_(4)through d-p and s-p synergistic orbital hybridization which facilitates the reduction of LiPS.Moreover,S-dominant p-d hybridization between Li_(2)S and a high-spin Mn site weakens the Li-S bond and facilitates the rapid sulfur evolution reaction.Consequently,the Li-S battery with a bifunctional HE-SA catalyst shows an ultralow capacity decay of 0.026% per cycle over 1900 cycles at 1 C.This work proposes a high-entropy strategy for sculpting electronic structures to enable spin and orbital hybridization modulation in advanced catalysts toward longcycling Li-S batteries.
基金financially supported by the VLAIO-Catalisti ICON project"Blue Plasma"(grant ID HBC.2022.0445)by the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant Agreement No.810182–SCOPE ERC Synergy project)the Horizon Europe Research and Innovation Action(Grant Agreement No.101172766—EffiTorch)。
文摘We present the performance of a post-plasma carbon bed for improving plasma-based CO_(2)conversion,studying the effect of bed length and additional thermal bed insulation.The experiments were conducted using an atmospheric pressure gliding arc plasmatron in both high and low specific energy input(SEI)regimes.Each bed was equipped with a silo to enable continuous carbon feeding and operation for an order of 1 h,thus overcoming previous limitations in literature.Importantly,we derive an improved energy efficiency(EE)calculation with an accurate and unambiguous consideration of the key reaction contributions of both plasma and carbon bed.This derivation serves to highlight the inconsistencies that arise in determining EE in such a complex chemical system.We therefore advise and advocate for the use of energy cost(EC)as the key reported energy metric in systems using post-plasma carbon beds.The optimum conversion and energy metrics were obtained with the longest bed,reaching a conversion of 41%,an EE of 51%and an EC of 0.41 MJ/mol at high SEI.The design of the insulated bed and silo allow for previously unreported preheating of the carbon,which reduces oscillations observed in the conversion profiles of the short and long beds.Preheating of the external silo for the long bed also yields a near-complete removal of oscillations.Finally,when comparing our performance with results from literature for postplasma carbon beds,our system clearly improves upon the state-of-the-art,both in absolute values of conversion and energy metrics at the same SEI,as well as by sustaining this improvement for extended periods of time.
基金supported by the National Natural Science Foundation of China(Grants nos.11775155,51561135013,21603202)。
文摘Conversion of CO2 into CO using plasma processing powered by renewable energy is a promising method to convert intermittent sustainable electricity into storable chemical energy.Despite extensive research efforts worldwide,there is currently no process that achieves economically viable values for both CO2 conversion fraction and energy recovery efficiency simultaneously.Here we demonstrate that a process that utilizes the Boudouard reaction,CO^2++C→2 CO,driven by a thermal plasma allows both 95%CO2 conversion to CO and energy recovery efficiency of 70%,values far higher than seen so far.By comparing the conversion process with and without CO2 excitation by a plasma and by using optical emission spectroscopy we show that the improved performance is due to a novel mode of operation where CO2 is pyrolyzed into an active mixture of CO,O and O2 by an arc discharge which is then introduced into a fixed bed to interact with carbon material.In this way,the free oxygen in the mixture combusts with carbon to form CO,and residual plasma excited CO2 is reduced by carbon.In the overall process,the endothermic Boudouard reaction is partially replaced by an exothermic reaction,and the excess electric energy to produce CO2 plasma is reused in the carbon bed.
基金financially supported by NSFC (Grant Nos.21621091,21373008)the National Key Research and Development Program of China (2016YFB0100202)
文摘Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electrochemical properties. The CoMn204 anode can deliver a large capacity of 1070 mAh g-1 in thefirst discharge, a reversible capacity of 500 mAh g^-1 after 100 cycles with a coulombic efficiency of 98.5% at a charge-discharge current density of 200 mA g^-l, and a specific capacity of 385 mAh g^-1 at a muchhigher charge-discharge current density of 1600mA g^-1. Synchrotron X-ray absorption fine structure（XAFS） techniques were applied to investigate the conversion reaction mechanism of the CoMn204 anode.The X-ray absorption near edge structure （XANES） spectra revealed that, in the first discharge-charge cy-cle, Co and Mn in CoMn204 were reduced to metallic Co and Mn when the electrode was discharged to0.01 V, while they were oxidized respectively to CoO and MnO when the electrode was charged to 3.0V.Experiments of both XANE5 and extended X-ray absorption fine structure （EXAFS） revealed that neithervalence evolution nor phase transition of the porous core-shell CoMn204 microspheres could happen inthe discharge plateau from 0.8 to 0.6V, which demonstrates the formation of solid electrolyte interface（SEI） on the anode.
基金the National Natural Science Foundation of China(21872144,21972140 and 91645117)Liaoning Revitalization Talents Program(XLYC1907053)+2 种基金CAS Youth Innovation Promotion Association(2018220)Talents Innovation Project of Dalian City(2017RQ032 and 2016RD04)China Postdoctoral Science Foundation(2019TQ0314,2018M641726 and 2019M661146)。
文摘Molybdenum carbides are highly active for CO2 conversion to CO via the reverse water-gas shift(RWGS)reaction, however the large grain size up to micrometers renders its relatively lower active sites utilization efficiency while generating CH4 as a by-product. In this work, a homogeneously dispersed molybdenum carbide hybrid catalyst with sub-nanosized cluster(the average size as small as 0.5 nm) is prepared via a facile carbothermal treatment for highly selective CO2-CO reduction. The partially disordered Mo2C clusters are characterized by synchrotron high-resolution XRD and atomic resolution HAADF-STEM analysis, for which the source cause of the disorder is pinpointed by XAFS analysis to be the nitrogen intercalants from the carbonaceous precursor. The partially disordered Mo2C clusters show a RWGS rate as high as 184.4 μmol gMo2C-1s-1 at 400 ℃ with a superior selectivity toward CO(> 99.5%). This work 2 highlights a facile strategy for fabricating highly dispersed and partially disordered Mo2C clusters at a sub-nano size with beneficial N-doping for delivering high catalytic activity and operational stability.
基金sponsored by the National Natural Science Foundation of China (Nos. 22208140 and 22078145)。
文摘The deep-processing utility of pure hydrogen sulfide (H_(2)S) is a significant direction in natural gas chemical industry.Herein,a brand-new strategy of H_(2)S conversion by a,β-unsaturated carboxylate esters into thiols or thioethers using task-specific carboxylate ionic liquids (ILs) as catalyst has been developed,firstly accomplishing the phase separation of product and catalyst without introducing the third component.It can be considered as a cascade reaction in which the product selectivity can be controlled by adjusting the molar ratio of H_(2)S to a,β-unsaturated carboxylate esters.Also,the effects of ILs with different anions and cations,intermittent feeding operations,as well as pressure-time kinetic behaviors on cascade reaction were investigated.Furthermore,the proposed interaction mechanism of H_(2)S conversion using butyl acrylate catalyzed by[Emim][Ac]was revealed by DFT-based theoretical calculation.The approach enables the self-phase separation promotion of catalyst and product and achieves 99%quantitative conversion under mild conditions in the absence of solvent,making the entire process ecologically benign.High-efficiency reaction activity can still be maintained after ten cycles of the catalyst.Therefore,the good results,combined with its simplicity of operation and the high recyclability of the catalyst,make this green method environmentally friendly and cost-effective.It is anticipated that this self-separation method mediated by task-specific ILs will provide a feasible strategy for H_(2)S utilization,which will guide its application on an industrial scale.
基金Ting-ting FENG acknowledges the financial support from Professor Paul V.BRAUN at Department of Materials Science and Engineering,University of Illinois at Urbana-Champaign,the support from Chinese Scholarship Council during her visit to University of Illinois at Urbana-Champaign,partial financial supports from Department of Science and Technology of Sichuan Province,China(2019YFH0002,2019YFG0222 and 2019YFG0526).The research was partly carried out in the Frederick Seitz Materials Research Laboratory Central Research Facilities,University of Illinois at Urbana-Champaign.
文摘The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.
基金supported by the National Key Research and Development Program of China (2016YFB0701100, 2017YFB0702800)the National Natural Science Foundation of China (21673295)~~
文摘The reaction mechanism of zeolite- or zeotype-catalyzed methanol-to-olefins（MTO） conversion is still a subject of debate. Employing periodic density functional theory calculations, the olefin-based cycle was studied using tetramethylethene（TME） as a representative olefinic hydrocarbon pool in H-SAPO-18 zeotype. The overall free energy barrier at 673 K was calculated and found to be less than 150 kJ/mol in the TME-based cycle, much lower than those in the aromatic-based cycle（〉 200 kJ/mol）, indicating that olefins themselves are the dominant active hydrocarbon pool species in H-SAPO-18. The similarity of the intermediates involved between the aromatic-based cycle and the olefin-based cycle was also highlighted, revealing that both cycles were pattern-consistent. The selectivity related to the distribution of cracking precursors, such as higher olefins or carbenium ions, as a result of the olefin-based cycle for the MTO conversion. The enthalpy barrier of the crack-ing step scaled linearly with the number of carbon atoms of cracking precursors to produce ethene or propene with ethene being much less favored than propene for cracking of C7 and higher pre-cursors. This work highlighted the importance of the olefin-based cycle in H-SAPO-18 for the MTO conversion and established the similarity between the olefin-based and aromatic-based cycles.
基金the National Natural Science Foundation of China (21703217, 11702264, 11702268, 11802276, 11772307) for financial support
文摘MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years.Herein,we report the intriguing light-to-heat conversion property of vanadium carbide(V_(2)C)MXene under irradiation of millisecond laser pulse.Unlike the typical photothermal materials,the V_(2)C MXene not only converts the incident laser energy to heat by the physical photothermal effect,but also triggers the exothermic oxidation of the V_(2)C MXene.The oxidation could be greatly promoted with addition of plasmonic Au nanorods(Au NRs)for light absorption enhancement.Owing to the unique light-to-heat conversion property,the Au NRs/V_(2)C MXene membrane could serve as high temperature pulse(HTP)generators that is proposed for numerous applications with high demand for immediacy.As a proof-of concept application,Au NRs/V_(2)C MXene membrane was applied for laser ignition of the high energy density materials,such as 2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane(HNIW or CL-20).An improved ignition performance,in terms of lowered laser threshold,is achieved as compared to the state-of-the-art light-to-heat conversion materials.
基金financially supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.NRF2019R1A2C2088047)。
文摘Efforts have been made to develop a promising anode material with a novel composition for sodiumion batteries(SIBs).In this study,the sodium-ion storage mechanism of transition metal selenite that comprises transition metal cation coupled with two anions is studied.Amorphous cobalt selenite(CoSeO_(3))-carbon composite nanofibers containing numerous pores are synthesized via electrospinning process.Upon heat treatment of the electrospun nanofibers containing selenium,CoSe_(2)nanoclusters are formed.During the subsequent oxidation,CoSe_(2)transformed into amorphous CoSeO_(3)and some part of carbon was oxidized into CO_(2),leaving the pores inside the nanofiber.To unveil the electrochemical reaction mechanism,analytical methods including cyclic voltammetry,ex-situ X-ray photoelectron spectroscopy,ex-situ transmission electron microscopy,and in-situ electrochemical impedance spectroscopy techniques were adopted.Based on the analyses,the following conversion reaction from the second cycle onward is suggested:CoO+xSeO_(2)+(1-x)Se+4(x+1)Na^(+)+4(x+1)e~-?Co+(2x+1)Na_(2)O+Na_(2)Se.Furthermore,the electrochemical properties of porous CoSeO_(3)-carbon composite nanofibers are analyzed in detail.The anode material exhibited stable cycle stability up to 200 cycles at 0.5 A g^(-1)and high rate performance up to 5 A g^(-1).
基金supported by the National Natural Science Foundation of China(52122308,21905253,51973200).
文摘Developing highly active and robust oxygen evolution reaction(OER)electrocatalysts is still a critical challenge for water electrolyzers and metal-air batteries.Realizing the dynamic evolution of the intermediate and charge transfer during OER and developing a clear OER mechanism is crucial to design high-performance OER catalysts.Recently in Nature,Xue and colleagues revealed a new OER mechanism,coupled oxygen evolution mechanism(COM),which involves a switchable metal and oxygen redox under light irradiation in nickel oxyhydroxide-based materials.This newly developed mechanism requires a reversible geometric conversion between octahedron(NiO_(6))and square planar(NiO_(4))to achieve electronic states with both“metal redox”and“oxygen redox”during OER.The asymmetric structure endows NR-NiOOH with a nonoverlapping region between the dz^(2) orbitals and a_(1g)^(*)bands,which facilitate the geometric conversion and enact the COM pathway.As a result,NR-NiOOH exhibited better OER activity and stability than the traditional NiOOH.
基金supported by the National Key Research and Development Program (no.2016YFA0202500)National Basic Research Program of China (2015CB932500)the Natural Scientific Foundation of China (nos.21306102 and 21422604)
文摘Nanostructured materials have received tremendous interest due to their unique mechanical/electrical properties and overall behavior contributed by the complex synergy of bulk and interfacial properties for efficient and effective energy conversion and storage. The booming development of nanotechnology affords emerging but effective tools in designing advanced energy material. We reviewed the significant progress and dominated nanostructured energy materials in electrochemical energy conversion and storage devices, including lithium ion batteries, lithium-sulfur batteries, lithium-oxygen batteries, lithium metal batteries, and supercapacitors. The use of nanostructured electrocatalyst for effective electrocatalysis in oxygen reduction and oxygen evolution reactions for fuel cells and metal-air batteries was also included. The challenges in the undesirable side reactions between electrolytes and electrode due to high electrode/electrolyte contact area, low volumetric energy density of electrode owing to low tap density, and uniform production of complex energy materials in working devices should be overcome to fully demonstrate the advanced energy nanostructures for electrochemical energy conversion and storage. The energy chemistry at the interfaces of nanostructured electrode/electrolyte is highly expected to guide the rational design and full demonstration of energy materials in a working device. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
基金supported by the National Key R&D Program(2017YFA0206804)the National Natural Science Foundation of China(21871021,21521005)the Fundamental Research Funds for the Central Universities(buctylkxj01,XK1802-6)~~
文摘Ethanol conversion to high-value-added products has attracted considerable attention in both academic research and industrial fields.In this study,we synthesized a series of tunable acid–base bifunctional Zn-Zr-Al metal oxides(represented as Zn2ZrxAl-MMO)in light of the structural topotactic transformation of Zn2ZrxAl-hydrotalcite precursors(Zn2ZrxAl-LDH).The resulting Zn2ZrxAl-MMO catalysts were employed in the conversion of ethanol to diethyl carbonate.The Zr^4+ ion content of the LDH precursor plays a key role in modulating the acid-base properties and determining catalytic performance:the Zn2Zr0.1Al-MMO sample exhibits the optimal catalytic behavior with a diethyl carbonate(DEC)yield of 42.1%,which is the highest reported for metal oxide catalysts.Structure-property correlation investigations revealed that the synergic catalysis between medium-strong basic sites and weak acid sites plays a predominant role in the catalytic behavior.Furthermore,in situ Fourier transform infrared measurements showed that the weak acidic site promotes activation adsorption of the reactant(urea)and the intermediate product(ethyl carbamate),while the medium-strong basic site accelerates ethanol activation.Moreover,the Zn2Zr0.1Al-MMO catalyst has the advantages of cost effectiveness,good stability,and reusability.Therefore,the acid-base bifunctional catalysts developed in this work can be employed as promising candidates in acid-base catalytic reactions such as ethanol conversion.
文摘Plasma methane (CH_4) conversion in gliding arc discharge was examined. Theresult data of experiments regarding the performance of gliding arc discharge were presented in thispaper. A simulation which is consisted some chemical kinetic mechanisms has been provided toanalyze and describe the plasma process. The effect of total gas flow rate and input frequencyrefers to power consumption have been studied to evaluate the performance of gliding arc plasmasystem and the reaction mechanism of decomposition. Experiment results indicated that the maximumconversion of CH_4 reached 50% at the total gas flow rate of 1 L/min. The plasma reaction wasoccurred at the atmospheric pressure and the main products were C (solid), hydrogen, and acetylene(C_2H_2). The plasma reaction of methane conversion was exothermic reaction which increased theproduct stream temperature around 30-50℃.
基金the financial support of the Scientific Research Projects Coordination Unit of Istanbul University (Project number: 17344 and 31088)
文摘Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and pseudomorphic conversion to SrC2 O4·H2O occurs. In the second step, SrC2 O4·H2O reacts with H2C2O4 to form H[Sr(C2 O4)1.5(H2O)]. Sr(HC2 O4)(C2 O4)0.5·H2 O crystallizes during cooling of the reaction mixture to room temperature if the solution reaches the saturation concentration of (H[Sr(C2O4)1.5(H2O)]. The aims of this study are the derivation of reaction rate equations and the determination of the kinetic parameters such as pre-exponential factor, apparent activation energy and order of H2C2O4 concentration for each reaction step.Fractional conversions of SrSO4 were calculated using the quantitative amounts of dissolved S and Sr. It was determined that the reaction rate increased at the initial time of reaction by increasing the temperature using solutions with approximately same H2C2O4 concentrations. The reaction extends very slowly after a certain time in solutions with low H2C2O4 concentration and ends by the formation of a protective layer of SrC2O4-H2O around the surfaces of solid particles. Fractional conversion of SrSO4 is increased by increasing concentration of H2C2O4 at constant temperature. Kinetic model equations were derived using shrinking core model for each step.
