Selective hydrodeoxygenation of lignin derivatives into aromatic compounds is a promising route for the upgrading of lignin feedstocks.Metal carbide catalysts have exhibited excellent selectivity in hydrodeoxygenation...Selective hydrodeoxygenation of lignin derivatives into aromatic compounds is a promising route for the upgrading of lignin feedstocks.Metal carbide catalysts have exhibited excellent selectivity in hydrodeoxygenation reactions,while their structure-activity relationship is still in ambiguity.Herein,a liquid-phase atomic layer deposition method was employed to synthesize W_(2)C/SiO_(2) catalysts with uniform and size-controllable W_(2)C nanoparticles.For gas-phase hydrodeoxygenation of lignin-derived m-cresol at 350℃,these W_(2)C/SiO_(2) catalysts showed superior toluene selectivities(>95%)regardless of the W_(2)C particle size.An optimal W_(2)C particle size of~7 nm was obtained for achieving the highest W_(2)C-based hydrodeoxygenation rate.In contrast,the turnover rate per surface W site increased almost monotonously as the W_(2)C particle size increased within 0.7-15 nm,attributable to high-index planes appeared on the larger W_(2)C nanoparticles.Kinetic effects of m-cresol and H_(2),taken together with temperature-programmed desorption of probe molecules and theoretical treatments,further indicate that the W_(2)C surface is nearly saturated by adsorbed m-cresol or its derivates under the reaction condition and the H-addition of the C7H7*intermediate to form toluene,instead of the initial C-O cleavage in m-cresol,acts as the rate-determining step.A side-by-side comparison between W_(2)C(102)and W_(2)C(001)catalyst surfaces in theoretical simulations of m-cresol hydrodeoxygenation verifies that high-index planes can stabilize kinetically-relevant transition states more effectively than the low-index ones,as a result of more available less-coordinated active sites on the former.The above findings bring new mechanistic insights into the site requirements of supported W_(2)C nanocatalysts,distinct from those metal-catalyzed hydrodeoxygenation of oxygenates.展开更多
The highly selective catalytic hydrogenation of halogenated nitroaromatics was achieved by employing Pd‑based catalysts that were co‑modified with organic and inorganic ligands.It was demonstrated that the catalysts c...The highly selective catalytic hydrogenation of halogenated nitroaromatics was achieved by employing Pd‑based catalysts that were co‑modified with organic and inorganic ligands.It was demonstrated that the catalysts contained Pd species in mixed valence states,with high valence Pd at the metal‑support interface and zero valence Pd at the metal surface.While the strong coordination of triphenylphosphine(PPh3)to Pd0 on the Pd surface prevents the adsorption of halogenated nitroaromatics and thus dehalogenation,the coordination of sodium metavanadate(NaVO3)to high‑valence Pd sites at the interface helps to activate H2 in a heterolytic pathway for the selective hydrogenation of nitro‑groups.The excellent catalytic performance of the interfacial active sites enables the selective hydrogenation of a wide range of halogenated nitroaromatics.展开更多
With its high theoretical capacity,lithium(Li)metal is recognized as the most potential anode for realizing a high-performance energy storage system.A series of questions(severe safety hazard,low Coulombic efficiency,...With its high theoretical capacity,lithium(Li)metal is recognized as the most potential anode for realizing a high-performance energy storage system.A series of questions(severe safety hazard,low Coulombic efficiency,short lifetime,etc.)induced by uncontrollable dendrites growth,unstable solid electrolyte interface layer,and large volume change,make practical application of Li-metal anodes still a threshold.Due to their highly appealing properties,carbon-based materials as hosts to composite with Li metal have been passionately investigated for improving the performance of Li-metal batteries.This review displays an overview of the critical role of carbon-based hosts for improving the comprehensive performance of Li-metal anodes.Based on correlated mainstream models,the main failure mechanism of Li-metal anodes is introduced.The advantages and strategies of carbon-based hosts to address the corresponding challenges are generalized.The unique function,existing limitation,and recent research progress of key carbon-based host materials for Li-metal anodes are reviewed.Finally,a conclusion and an outlook for future research of carbon-based hosts are presented.This review is dedicated to summarizing the advances of carbon-based materials hosts in recent years and providing a reference for the further development of carbonbased hosts for advanced Li-metal anodes.展开更多
To study the mechanism of formation and inhibition of Ce conversion films on Al 2024-T3 alloy, scanning microreference electrode technique (SMRE) is used to probe the potential map on Al 2024-T3 in CeCl 3 solution, t...To study the mechanism of formation and inhibition of Ce conversion films on Al 2024-T3 alloy, scanning microreference electrode technique (SMRE) is used to probe the potential map on Al 2024-T3 in CeCl 3 solution, the localized corrosion of Al alloy decreases with immersion time and disappears finally, which results from the competition of Cl - aggression and Ce 3+ inhibition on alloy surface. The results of X-ray photoelectron spectroscopy (XPS) indicate that the Ce conversion films consist of Al 2O 3, CeO 2 and Ce 2O 3(Ce(OH) 3), and CeO 2/Ce 2O 3 ratio decreases with the immersion time. When a critical pH for Ce(OH) 3 formation was reached, Ce(OH) 3 will precipitate on the micro cathodic area on alloy surface. Consequently, H 2O 2, the product of the catholic reaction will oxidize a part of Ce(OH) 3 to CeO 2, which appears a better corrosion resistance for Al alloys.展开更多
The sodium potassium citrato oxotungstate(VI) dimer, Na 4K 2〔W 2O 5\|(cit) 2〕·11H 2O (H 4cit = citric acid) was obtained by the reaction of sodium tungstate(VI) and excess potassium citrate monobasic (KH 3cit) ...The sodium potassium citrato oxotungstate(VI) dimer, Na 4K 2〔W 2O 5\|(cit) 2〕·11H 2O (H 4cit = citric acid) was obtained by the reaction of sodium tungstate(VI) and excess potassium citrate monobasic (KH 3cit) in neutral solution. The crystal data for the title compound: monoclinic, C 12 H 30 K 2Na 4W 2O 30 , M r =1192.21, space group P2 1/n, a=17.427(4), b=10.022(2), c=18.637(3) , β=92.62(1)°, V=3252(2) 3, Z=4, D c =2.435 g/cm 3, μ( Mo Kα )=76.38 cm -1 , F( 000)=2288. The structure was refined to R =0.0434 for 6327 independent observed reflections with I>3σ(I) . The complex anion contains a quasi centrosymmetric (O 2W)O b(WO 2) core with a bent bridging oxo group 〔W-O b-W 175.0(4)°〕. Each citrate as tridentate ligand coordinates to a tungsten atom through the alkoxy, α carboxyl, and one β carboxyl group, while the other β carboxyl group remains uncoordinated. Principal dimensions are: W-O b 1.883(6) , (W=O t)av 1.715(6) , W-O (alkoxy) 1.959(6) , W-O ( α carboxy) 2.176(6) and W-O ( β carboxy) 2.231(6) . The tungsten atom is located in a distorted octahedron environment.展开更多
Precursor decomposition was used for the preparation of VTeO/SBA-15 catalyst for the selective oxidation of propane to acrolein. The catalyst shows a better performance compared with those prepared by conventional imp...Precursor decomposition was used for the preparation of VTeO/SBA-15 catalyst for the selective oxidation of propane to acrolein. The catalyst shows a better performance compared with those prepared by conventional impregnant method. A yield of 9.3% of acrolein was achieved with 2% V loadings at 500 ℃. XRD, N2-adsorption, H2-TPR, Py-IR and XPS measurements were used to unclose the relationship between the structure and performance of the catalyst.展开更多
Lithium cobalt oxide(LCO)is the dominating cathode materials for lithium-ion batteries(LIBs)deployed in consumer electronic devices for its superior volumetric energy density and electrochemical performances.The const...Lithium cobalt oxide(LCO)is the dominating cathode materials for lithium-ion batteries(LIBs)deployed in consumer electronic devices for its superior volumetric energy density and electrochemical performances.The constantly increasing demands of higher energy density urge to develop high-voltage LCO via a variety of strategies.However,the corresponding modification mechanism,especially the influence of the long-and short-range structural transitions at high-voltage on electrochemical performance,is still not well understood and needs further exploration.Based on ss-NMR,in-situ X-ray diffraction,and electrochemical performance results,it is revealed that the H3 to H1-3 phase transition dictates the structural reversibility and stability of LCO,thereby determining the electrochemical performance.The introduction of La and Al ions could postpone the appearance of H1-3 phase and induce various types of local environments to alleviate the volume variation at the atomic level,leading to better reversibility of the H1-3 phase and smaller lattice strain,and significantly improved cycle performance.Such a comprehensive long-range,local,and electronic structure characterization enables an in-depth understanding of the structural evolution of LCO,providing a guiding principle for developing high-voltage LCO for high energy density LIBs.展开更多
MCM 41 molecular sieve supported Rh PPh 3 catalysts were prepared by the in situ assembling of the metal complex from smaller moieties of Rh(acac)(CO) 2 and ligand of PPh 3. The resulted vip/host materials(Rh PPh 3/...MCM 41 molecular sieve supported Rh PPh 3 catalysts were prepared by the in situ assembling of the metal complex from smaller moieties of Rh(acac)(CO) 2 and ligand of PPh 3. The resulted vip/host materials(Rh PPh 3/MCM 41) were characterized by X ray powder diffraction, FTIR and 31 P( 1H) NMR, and served as catalysts for propene hydroformylation. The results showed negligible change in MCM 41 framework after propene hydroformylation at 393 K. Higher hydroformylation activities were obtained on Rh PPh 3/MCM 41 catalysts compared to that on Rh PPh 3/SiO 2.展开更多
The active sites of samarium orthovanadate(SmVO 4) were studied by means of ESR, NO TPD and temperature programmed 18 O 2 isotope exchange(TPIE) methods. The results of ESR and NO TPD confirm the presenc...The active sites of samarium orthovanadate(SmVO 4) were studied by means of ESR, NO TPD and temperature programmed 18 O 2 isotope exchange(TPIE) methods. The results of ESR and NO TPD confirm the presence of V 4+ in the catalyst. The TPIE revealed that the 18 O 2 isotope exchange was carried out through a single exchange procedure. The V 4+ species associated with oxygen vacancies are the sites for O 2 activation.展开更多
Four FeCO states with 3d4s and 3d3d electrons spinpaired or spinunpaired were examined to investigate the influences of pairing versus unpairing mechanisms upon the bonding and interaction in FeCO.The calculation resu...Four FeCO states with 3d4s and 3d3d electrons spinpaired or spinunpaired were examined to investigate the influences of pairing versus unpairing mechanisms upon the bonding and interaction in FeCO.The calculation results show that the FeCO bonding and interaction are determined by a balance between the bonding stabilization and the exchange stabilization with 3d4s electron spinpairing or without it.The 3d3d electron spinpairing versus unpairing has a surprised effect on the FeCO bonding properties even though the 3d orbitals are usually considered as non bonding ones.展开更多
The electronic structure of the perovskite LaCoO3 at room temperature structure （293 K） was calculated by using PBE, PBE＋U and HSE. Different spin configurations have been considered. Our calculations showed that t...The electronic structure of the perovskite LaCoO3 at room temperature structure （293 K） was calculated by using PBE, PBE＋U and HSE. Different spin configurations have been considered. Our calculations showed that the choice of the Hubbard U parameter in DFT＋U and mixing factor α in HSE significantly influenced the band gap as well as relative energies. For the spin exited states, the optimal value for U and α were 3.0 eV and 0.05, respectively. Our calculation also emphasized that when U〉5.0 eV, PBE＋U would lead to unreasonable electronic structure and energy order.展开更多
Lithium metal is considered as the ultimate anode material for the next generation of high-energy density batteries.However,non-uniform lithium dendrite growth,serious electrolyte consumption,and significant volume ch...Lithium metal is considered as the ultimate anode material for the next generation of high-energy density batteries.However,non-uniform lithium dendrite growth,serious electrolyte consumption,and significant volume changes during lithium deposition/stripping processes lead to sustained accumulation of inactive lithium and poor cycling reversibility.Quantifying the formation and evolution of inactive lithium under different conditions and fully evaluating the complex failure modes are the key issues in this challenging field.This article comprehensively reviews recent research progress on the quantification of formation and evolution of inactive lithium detected by different quantitative techniques in rechargeable lithium metal batteries.The key research challenges such as failure mechanism,modification strategies and operando characterization of lithium metal anodes are systematically summarized and prospected.This review provides a new angle of view to understand failure mechanism of lithium metal anodes and inspiration and guidance for the future development of rechargeable lithium metal batteries.展开更多
α-Keggin polyoxometalates(POMs)[XW_(12)O_(40)]^(n−)(X=Al,Si,P,S)are widely used in batteries owing to their remarkable redox activity.However,the mechanism underlying the applications appears inconsistent with the wi...α-Keggin polyoxometalates(POMs)[XW_(12)O_(40)]^(n−)(X=Al,Si,P,S)are widely used in batteries owing to their remarkable redox activity.However,the mechanism underlying the applications appears inconsistent with the widely accepted covalent bonding nature.Here,first-principles calculations show that XW_(12)are core–shell structures composed of a shell and an XO_(4)^(n−)core,both are stabilized by covalent interactions.Interestingly,owing to the presence of a substantial number of electrons in W_(12)O_(36)shell,the frontier molecular orbitals of XW_(12)are not only strongly delocalized but also exhibit superatomic properties with high-angular momentum electrons that do not conform to the Jellium model.Detailed analysis indicates that energetically high lying filled molecular orbitals(MOs)have reached unusually high-angular momentum characterized by quantum number K or higher,allowing for the accommodation of numerous electrons.This attribute confers strong electron acceptor ability and redox activity to XW_(12).Moreover,electrons added to XW_(12)still occupy the K orbitals and will not cause rearrangement of the MOs,thereby maintaining the stability of these structures.Our findings highlight the structure–activity relationship and provide a direction for tailor-made POMs with specific properties at atomic level.展开更多
Operando monitoring of internal and local electrochemical processes within lithium-ion batteries(LIBs)is crucial,necessitating a range of non-invasive,real-time imaging characterization techniques including nuclear ma...Operando monitoring of internal and local electrochemical processes within lithium-ion batteries(LIBs)is crucial,necessitating a range of non-invasive,real-time imaging characterization techniques including nuclear magnetic resonance(NMR)techniques.This review provides a comprehensive overview of the recent applications and advancements of non-invasive magnetic resonance imaging(MRI)techniques in LIBs.It initially introduces the principles and hardware of MRI,followed by a detailed summary and comparison of MRI techniques used for characterizing liquid/solid electrolytes,electrodes and commercial batteries.This encompasses the determination of electrolytes'transport properties,acquisition of ion distribution profile,and diagnosis of battery defects.By focusing on experimental parameters and optimization strategies,our goal is to explore MRI methods suitable to a variety of research subjects,aiming to enhance imaging quality across diverse scenarios and offer critical physical/chemical insights into the ongoing operation processes of LIBs.展开更多
Ethyl-(2,2,2-trifluoroethyl)carbonate(ETFEC)is investigated as a solvent component in high-voltage electrolytes for LiNi0.5Mn1.5O4(LNMO).Our results show that the self-discharge behavior and the high temperature cycle...Ethyl-(2,2,2-trifluoroethyl)carbonate(ETFEC)is investigated as a solvent component in high-voltage electrolytes for LiNi0.5Mn1.5O4(LNMO).Our results show that the self-discharge behavior and the high temperature cycle performance can be significantly improved by the addition of 10%ETFEC into the normal carbonate electrolytes,e.g.,the capacity retention improved from 65.3%to 77.1%after 200 cycles at 60℃.The main reason can be ascribed to the high stability of ETFEC which prevents large oxidation of the electrolyte on the cathode surface.In addition,we also explore the feasibility of electrolytes using single fluoriated-solvents with and without additives.Our results show that the cycle performance of LNMO material can be greatly improved in 1 MLiPF6+pure ETFEC-solvent system with 2 wt%ethylene carbonate(EC)or ethylene sulfate(DTD).The capacity retention of the LNMO materials is 93%after 300 cycles,even better than that of carbonate-based electrolytes.It is shown that the additives are oxidized on the surface of LNMO particles and contribute to the formation of cathode/electrolyte interphase(CEI)films.This composite CEI film plays a crucial role in suppressing the serious decomposition of the electrolyte at high voltage.展开更多
Lithium(Li) metal is considered as the most promising anode material for the next-generation high performance Li batteries.However,the uncontrollable dendritic growth impedes its commercial application.Herein,we desig...Lithium(Li) metal is considered as the most promising anode material for the next-generation high performance Li batteries.However,the uncontrollable dendritic growth impedes its commercial application.Herein,we design a 3 D Si@carbon nanofibers(CNFs)@ZnO-ZnO-Cu skeleton(SCZ) for guiding the homogeneous bottom-growth of Li metal.The top LixSi@CNFs and bottom LiyZn@CNFs layers could form conductivity and overpotential gradient to avoid the "top-growth" of Li metal.Moreover,the top lithiophilic LixSi@CNFs layer could regulate the nucleation and deposition of Li-ions even if the lithium dendrites grow out of the skeleton under high capacity Li deposition(30 mAh cm^(-2)).As a result,the SCZ-Li||LiFePO_(4) full cell delivers a high capacity of ~104 mAh g^(-1)(~94.82% capacity retention) after 2000 cycles at 5 C, elucidating the potential application of the 3 D double-gradient Li metal composite anode.展开更多
Atomically dispersed catalysts have shown promising prospects in catalysis studies.Among all of the developed methods for synthesizing atomically dispersed catalysts,the photochemical approach has recently aroused muc...Atomically dispersed catalysts have shown promising prospects in catalysis studies.Among all of the developed methods for synthesizing atomically dispersed catalysts,the photochemical approach has recently aroused much attention owing to its simple procedure and mild preparation conditions involved.In the present study,we demonstrate the application of the photochemical method to synthesize atomically dispersed Pd catalysts on(001)‐exposed anatase nanocrystals and commercial TiO2(P25).The as‐prepared catalysts exhibit both high activity and stability in the hydrogenation of styrene and catalytic oxidation of CO.展开更多
In the search of alternative resources to make commodity chemicals and transportation fuels for a low carbon future,lignocellulosic biomass with over 180-billion-ton annual production rate has been identified as a pro...In the search of alternative resources to make commodity chemicals and transportation fuels for a low carbon future,lignocellulosic biomass with over 180-billion-ton annual production rate has been identified as a promising feedstock.This review focuses on the state-of-the-art catalytic transformation of lignocellulosic biomass into value-added chemicals and fuels.Following a brief introduction on the structure,major resources and pretreatment methods of lignocellulosic biomass,the catalytic conversion of three main components,i.e.,cellulose,hemicellulose and lignin,into various compounds are comprehensively discussed.Either in separate steps or in one-pot,cellulose and hemicellulose are hydrolyzed into sugars and upgraded into oxygen-containing chemicals such as 5-HMF,furfural,polyols,and organic acids,or even nitrogen-containing chemicals such as amino acids.On the other hand,lignin is first depolymerized into phenols,catechols,guaiacols,aldehydes and ketones,and then further transformed into hydrocarbon fuels,bioplastic precursors and bioactive compounds.The review then introduces the transformations of whole biomass via catalytic gasification,catalytic pyrolysis,as well as emerging strategies.Finally,opportunities,challenges and prospective of woody biomass valorization are highlighted.展开更多
A detailed investigation on Pb-Ca-Sn alloys was made in order to choose suitable grid alloys materials for thin plate lead-acid batteries. The electrochemical performances of alloys were investigated by electrochemica...A detailed investigation on Pb-Ca-Sn alloys was made in order to choose suitable grid alloys materials for thin plate lead-acid batteries. The electrochemical performances of alloys were investigated by electrochemical corrosion experiment, scanning electron microscope (SEM), and cyclic voltammetry (CV) test. The results indicate that Pb-Ca-Sn-Bi-Cu alloys can be used to make the grids used for thin grid lead-acid batteries, the content of bismuth has primary effects on the corrosion resistance of grid alloys, the composition of alloys plays an important role on batteries performance, and appropriate scale of elements can be choosed to obtain optimal electrochemical performance. The lead-acid batteries using this kind of grid show good performance by cycle life test.展开更多
文摘Selective hydrodeoxygenation of lignin derivatives into aromatic compounds is a promising route for the upgrading of lignin feedstocks.Metal carbide catalysts have exhibited excellent selectivity in hydrodeoxygenation reactions,while their structure-activity relationship is still in ambiguity.Herein,a liquid-phase atomic layer deposition method was employed to synthesize W_(2)C/SiO_(2) catalysts with uniform and size-controllable W_(2)C nanoparticles.For gas-phase hydrodeoxygenation of lignin-derived m-cresol at 350℃,these W_(2)C/SiO_(2) catalysts showed superior toluene selectivities(>95%)regardless of the W_(2)C particle size.An optimal W_(2)C particle size of~7 nm was obtained for achieving the highest W_(2)C-based hydrodeoxygenation rate.In contrast,the turnover rate per surface W site increased almost monotonously as the W_(2)C particle size increased within 0.7-15 nm,attributable to high-index planes appeared on the larger W_(2)C nanoparticles.Kinetic effects of m-cresol and H_(2),taken together with temperature-programmed desorption of probe molecules and theoretical treatments,further indicate that the W_(2)C surface is nearly saturated by adsorbed m-cresol or its derivates under the reaction condition and the H-addition of the C7H7*intermediate to form toluene,instead of the initial C-O cleavage in m-cresol,acts as the rate-determining step.A side-by-side comparison between W_(2)C(102)and W_(2)C(001)catalyst surfaces in theoretical simulations of m-cresol hydrodeoxygenation verifies that high-index planes can stabilize kinetically-relevant transition states more effectively than the low-index ones,as a result of more available less-coordinated active sites on the former.The above findings bring new mechanistic insights into the site requirements of supported W_(2)C nanocatalysts,distinct from those metal-catalyzed hydrodeoxygenation of oxygenates.
文摘The highly selective catalytic hydrogenation of halogenated nitroaromatics was achieved by employing Pd‑based catalysts that were co‑modified with organic and inorganic ligands.It was demonstrated that the catalysts contained Pd species in mixed valence states,with high valence Pd at the metal‑support interface and zero valence Pd at the metal surface.While the strong coordination of triphenylphosphine(PPh3)to Pd0 on the Pd surface prevents the adsorption of halogenated nitroaromatics and thus dehalogenation,the coordination of sodium metavanadate(NaVO3)to high‑valence Pd sites at the interface helps to activate H2 in a heterolytic pathway for the selective hydrogenation of nitro‑groups.The excellent catalytic performance of the interfacial active sites enables the selective hydrogenation of a wide range of halogenated nitroaromatics.
基金The author sincerely thanks the financial supports from the National Natural Science Foundation of China(Grant Nos.51871188,51701169,and 51931006)National Key R&D Program of China(Grant No.2016YFA0202602)+1 种基金the Natural Science Foundation of Fujian Province of China(Grant No.2019J06003)the“Double‐First Class”Foundation of Materials and Intelligent Manufacturing Discipline of Xiamen University.
文摘With its high theoretical capacity,lithium(Li)metal is recognized as the most potential anode for realizing a high-performance energy storage system.A series of questions(severe safety hazard,low Coulombic efficiency,short lifetime,etc.)induced by uncontrollable dendrites growth,unstable solid electrolyte interface layer,and large volume change,make practical application of Li-metal anodes still a threshold.Due to their highly appealing properties,carbon-based materials as hosts to composite with Li metal have been passionately investigated for improving the performance of Li-metal batteries.This review displays an overview of the critical role of carbon-based hosts for improving the comprehensive performance of Li-metal anodes.Based on correlated mainstream models,the main failure mechanism of Li-metal anodes is introduced.The advantages and strategies of carbon-based hosts to address the corresponding challenges are generalized.The unique function,existing limitation,and recent research progress of key carbon-based host materials for Li-metal anodes are reviewed.Finally,a conclusion and an outlook for future research of carbon-based hosts are presented.This review is dedicated to summarizing the advances of carbon-based materials hosts in recent years and providing a reference for the further development of carbonbased hosts for advanced Li-metal anodes.
文摘To study the mechanism of formation and inhibition of Ce conversion films on Al 2024-T3 alloy, scanning microreference electrode technique (SMRE) is used to probe the potential map on Al 2024-T3 in CeCl 3 solution, the localized corrosion of Al alloy decreases with immersion time and disappears finally, which results from the competition of Cl - aggression and Ce 3+ inhibition on alloy surface. The results of X-ray photoelectron spectroscopy (XPS) indicate that the Ce conversion films consist of Al 2O 3, CeO 2 and Ce 2O 3(Ce(OH) 3), and CeO 2/Ce 2O 3 ratio decreases with the immersion time. When a critical pH for Ce(OH) 3 formation was reached, Ce(OH) 3 will precipitate on the micro cathodic area on alloy surface. Consequently, H 2O 2, the product of the catholic reaction will oxidize a part of Ce(OH) 3 to CeO 2, which appears a better corrosion resistance for Al alloys.
文摘The sodium potassium citrato oxotungstate(VI) dimer, Na 4K 2〔W 2O 5\|(cit) 2〕·11H 2O (H 4cit = citric acid) was obtained by the reaction of sodium tungstate(VI) and excess potassium citrate monobasic (KH 3cit) in neutral solution. The crystal data for the title compound: monoclinic, C 12 H 30 K 2Na 4W 2O 30 , M r =1192.21, space group P2 1/n, a=17.427(4), b=10.022(2), c=18.637(3) , β=92.62(1)°, V=3252(2) 3, Z=4, D c =2.435 g/cm 3, μ( Mo Kα )=76.38 cm -1 , F( 000)=2288. The structure was refined to R =0.0434 for 6327 independent observed reflections with I>3σ(I) . The complex anion contains a quasi centrosymmetric (O 2W)O b(WO 2) core with a bent bridging oxo group 〔W-O b-W 175.0(4)°〕. Each citrate as tridentate ligand coordinates to a tungsten atom through the alkoxy, α carboxyl, and one β carboxyl group, while the other β carboxyl group remains uncoordinated. Principal dimensions are: W-O b 1.883(6) , (W=O t)av 1.715(6) , W-O (alkoxy) 1.959(6) , W-O ( α carboxy) 2.176(6) and W-O ( β carboxy) 2.231(6) . The tungsten atom is located in a distorted octahedron environment.
基金Supported by the Ministry of Science and Technology of China(No. 2005CB221408)the National Natural Science Founda-tion of China(Nos. 20423002, 20571061)Key Scientific Project of Fujian Province, China(No. 2005HZ01-3)
文摘Precursor decomposition was used for the preparation of VTeO/SBA-15 catalyst for the selective oxidation of propane to acrolein. The catalyst shows a better performance compared with those prepared by conventional impregnant method. A yield of 9.3% of acrolein was achieved with 2% V loadings at 500 ℃. XRD, N2-adsorption, H2-TPR, Py-IR and XPS measurements were used to unclose the relationship between the structure and performance of the catalyst.
基金funded by the National Natural Science Foundation of China(grant no.21761132030,21935009)National Key Research and Development Program of China(grant no.2016YFB0901502,2018YFB0905400)Collaboration project between Ningde City&Xiamen University(2017c002)。
文摘Lithium cobalt oxide(LCO)is the dominating cathode materials for lithium-ion batteries(LIBs)deployed in consumer electronic devices for its superior volumetric energy density and electrochemical performances.The constantly increasing demands of higher energy density urge to develop high-voltage LCO via a variety of strategies.However,the corresponding modification mechanism,especially the influence of the long-and short-range structural transitions at high-voltage on electrochemical performance,is still not well understood and needs further exploration.Based on ss-NMR,in-situ X-ray diffraction,and electrochemical performance results,it is revealed that the H3 to H1-3 phase transition dictates the structural reversibility and stability of LCO,thereby determining the electrochemical performance.The introduction of La and Al ions could postpone the appearance of H1-3 phase and induce various types of local environments to alleviate the volume variation at the atomic level,leading to better reversibility of the H1-3 phase and smaller lattice strain,and significantly improved cycle performance.Such a comprehensive long-range,local,and electronic structure characterization enables an in-depth understanding of the structural evolution of LCO,providing a guiding principle for developing high-voltage LCO for high energy density LIBs.
基金Supported by the National Natural Science Foundation of China(Nos.2 98730 372 0 0 2 30 0 1and2 0 0 2 10 0 2 ) State KeyProject for Fundamental Research(No.G2 0 0 0 0 4 80 8) and the Ministry of Education of China
文摘MCM 41 molecular sieve supported Rh PPh 3 catalysts were prepared by the in situ assembling of the metal complex from smaller moieties of Rh(acac)(CO) 2 and ligand of PPh 3. The resulted vip/host materials(Rh PPh 3/MCM 41) were characterized by X ray powder diffraction, FTIR and 31 P( 1H) NMR, and served as catalysts for propene hydroformylation. The results showed negligible change in MCM 41 framework after propene hydroformylation at 393 K. Higher hydroformylation activities were obtained on Rh PPh 3/MCM 41 catalysts compared to that on Rh PPh 3/SiO 2.
文摘The active sites of samarium orthovanadate(SmVO 4) were studied by means of ESR, NO TPD and temperature programmed 18 O 2 isotope exchange(TPIE) methods. The results of ESR and NO TPD confirm the presence of V 4+ in the catalyst. The TPIE revealed that the 18 O 2 isotope exchange was carried out through a single exchange procedure. The V 4+ species associated with oxygen vacancies are the sites for O 2 activation.
文摘Four FeCO states with 3d4s and 3d3d electrons spinpaired or spinunpaired were examined to investigate the influences of pairing versus unpairing mechanisms upon the bonding and interaction in FeCO.The calculation results show that the FeCO bonding and interaction are determined by a balance between the bonding stabilization and the exchange stabilization with 3d4s electron spinpairing or without it.The 3d3d electron spinpairing versus unpairing has a surprised effect on the FeCO bonding properties even though the 3d orbitals are usually considered as non bonding ones.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.21033006, No.21133004, and No.21373167） and the Ministry of Science and Technology （No.2010CB732303）.
文摘The electronic structure of the perovskite LaCoO3 at room temperature structure （293 K） was calculated by using PBE, PBE＋U and HSE. Different spin configurations have been considered. Our calculations showed that the choice of the Hubbard U parameter in DFT＋U and mixing factor α in HSE significantly influenced the band gap as well as relative energies. For the spin exited states, the optimal value for U and α were 3.0 eV and 0.05, respectively. Our calculation also emphasized that when U〉5.0 eV, PBE＋U would lead to unreasonable electronic structure and energy order.
基金financially supported by the National Key R&D Program of China, Grant No. 2021YFB2401800
文摘Lithium metal is considered as the ultimate anode material for the next generation of high-energy density batteries.However,non-uniform lithium dendrite growth,serious electrolyte consumption,and significant volume changes during lithium deposition/stripping processes lead to sustained accumulation of inactive lithium and poor cycling reversibility.Quantifying the formation and evolution of inactive lithium under different conditions and fully evaluating the complex failure modes are the key issues in this challenging field.This article comprehensively reviews recent research progress on the quantification of formation and evolution of inactive lithium detected by different quantitative techniques in rechargeable lithium metal batteries.The key research challenges such as failure mechanism,modification strategies and operando characterization of lithium metal anodes are systematically summarized and prospected.This review provides a new angle of view to understand failure mechanism of lithium metal anodes and inspiration and guidance for the future development of rechargeable lithium metal batteries.
基金supported by the National Natural Science Foundation of China(under grant numbers 12174272 and 11974136)。
文摘α-Keggin polyoxometalates(POMs)[XW_(12)O_(40)]^(n−)(X=Al,Si,P,S)are widely used in batteries owing to their remarkable redox activity.However,the mechanism underlying the applications appears inconsistent with the widely accepted covalent bonding nature.Here,first-principles calculations show that XW_(12)are core–shell structures composed of a shell and an XO_(4)^(n−)core,both are stabilized by covalent interactions.Interestingly,owing to the presence of a substantial number of electrons in W_(12)O_(36)shell,the frontier molecular orbitals of XW_(12)are not only strongly delocalized but also exhibit superatomic properties with high-angular momentum electrons that do not conform to the Jellium model.Detailed analysis indicates that energetically high lying filled molecular orbitals(MOs)have reached unusually high-angular momentum characterized by quantum number K or higher,allowing for the accommodation of numerous electrons.This attribute confers strong electron acceptor ability and redox activity to XW_(12).Moreover,electrons added to XW_(12)still occupy the K orbitals and will not cause rearrangement of the MOs,thereby maintaining the stability of these structures.Our findings highlight the structure–activity relationship and provide a direction for tailor-made POMs with specific properties at atomic level.
基金supported by the National Key R&D Program of China,Grant No.2021YFB2401800。
文摘Operando monitoring of internal and local electrochemical processes within lithium-ion batteries(LIBs)is crucial,necessitating a range of non-invasive,real-time imaging characterization techniques including nuclear magnetic resonance(NMR)techniques.This review provides a comprehensive overview of the recent applications and advancements of non-invasive magnetic resonance imaging(MRI)techniques in LIBs.It initially introduces the principles and hardware of MRI,followed by a detailed summary and comparison of MRI techniques used for characterizing liquid/solid electrolytes,electrodes and commercial batteries.This encompasses the determination of electrolytes'transport properties,acquisition of ion distribution profile,and diagnosis of battery defects.By focusing on experimental parameters and optimization strategies,our goal is to explore MRI methods suitable to a variety of research subjects,aiming to enhance imaging quality across diverse scenarios and offer critical physical/chemical insights into the ongoing operation processes of LIBs.
基金financially supported by National Key Research and Development Program of China(Grant no.2018YFB010440)the National Natural Science Foundation of China(Grant nos.21761132030,21621091).
文摘Ethyl-(2,2,2-trifluoroethyl)carbonate(ETFEC)is investigated as a solvent component in high-voltage electrolytes for LiNi0.5Mn1.5O4(LNMO).Our results show that the self-discharge behavior and the high temperature cycle performance can be significantly improved by the addition of 10%ETFEC into the normal carbonate electrolytes,e.g.,the capacity retention improved from 65.3%to 77.1%after 200 cycles at 60℃.The main reason can be ascribed to the high stability of ETFEC which prevents large oxidation of the electrolyte on the cathode surface.In addition,we also explore the feasibility of electrolytes using single fluoriated-solvents with and without additives.Our results show that the cycle performance of LNMO material can be greatly improved in 1 MLiPF6+pure ETFEC-solvent system with 2 wt%ethylene carbonate(EC)or ethylene sulfate(DTD).The capacity retention of the LNMO materials is 93%after 300 cycles,even better than that of carbonate-based electrolytes.It is shown that the additives are oxidized on the surface of LNMO particles and contribute to the formation of cathode/electrolyte interphase(CEI)films.This composite CEI film plays a crucial role in suppressing the serious decomposition of the electrolyte at high voltage.
基金financial support from the National Natural Science Foundation of China(Grant Nos.51701169,51871188 and 51931006)the National Key R&D Program of China(Grant No.2016YFA0202602)+1 种基金the Natural Science Foundation of Fujian Province of China(No.2019J06003)the "Double-First Class" Foundation of Materials and Intelligent Manufacturing Discipline of Xiamen University。
文摘Lithium(Li) metal is considered as the most promising anode material for the next-generation high performance Li batteries.However,the uncontrollable dendritic growth impedes its commercial application.Herein,we design a 3 D Si@carbon nanofibers(CNFs)@ZnO-ZnO-Cu skeleton(SCZ) for guiding the homogeneous bottom-growth of Li metal.The top LixSi@CNFs and bottom LiyZn@CNFs layers could form conductivity and overpotential gradient to avoid the "top-growth" of Li metal.Moreover,the top lithiophilic LixSi@CNFs layer could regulate the nucleation and deposition of Li-ions even if the lithium dendrites grow out of the skeleton under high capacity Li deposition(30 mAh cm^(-2)).As a result,the SCZ-Li||LiFePO_(4) full cell delivers a high capacity of ~104 mAh g^(-1)(~94.82% capacity retention) after 2000 cycles at 5 C, elucidating the potential application of the 3 D double-gradient Li metal composite anode.
基金supported by the Ministry of Science and Technology of nano major research projects(2015CB932303)the National Natural Science Foundation of China(21420102001,21131005,21333008,21390390)~~
文摘Atomically dispersed catalysts have shown promising prospects in catalysis studies.Among all of the developed methods for synthesizing atomically dispersed catalysts,the photochemical approach has recently aroused much attention owing to its simple procedure and mild preparation conditions involved.In the present study,we demonstrate the application of the photochemical method to synthesize atomically dispersed Pd catalysts on(001)‐exposed anatase nanocrystals and commercial TiO2(P25).The as‐prepared catalysts exhibit both high activity and stability in the hydrogenation of styrene and catalytic oxidation of CO.
文摘In the search of alternative resources to make commodity chemicals and transportation fuels for a low carbon future,lignocellulosic biomass with over 180-billion-ton annual production rate has been identified as a promising feedstock.This review focuses on the state-of-the-art catalytic transformation of lignocellulosic biomass into value-added chemicals and fuels.Following a brief introduction on the structure,major resources and pretreatment methods of lignocellulosic biomass,the catalytic conversion of three main components,i.e.,cellulose,hemicellulose and lignin,into various compounds are comprehensively discussed.Either in separate steps or in one-pot,cellulose and hemicellulose are hydrolyzed into sugars and upgraded into oxygen-containing chemicals such as 5-HMF,furfural,polyols,and organic acids,or even nitrogen-containing chemicals such as amino acids.On the other hand,lignin is first depolymerized into phenols,catechols,guaiacols,aldehydes and ketones,and then further transformed into hydrocarbon fuels,bioplastic precursors and bioactive compounds.The review then introduces the transformations of whole biomass via catalytic gasification,catalytic pyrolysis,as well as emerging strategies.Finally,opportunities,challenges and prospective of woody biomass valorization are highlighted.
文摘A detailed investigation on Pb-Ca-Sn alloys was made in order to choose suitable grid alloys materials for thin plate lead-acid batteries. The electrochemical performances of alloys were investigated by electrochemical corrosion experiment, scanning electron microscope (SEM), and cyclic voltammetry (CV) test. The results indicate that Pb-Ca-Sn-Bi-Cu alloys can be used to make the grids used for thin grid lead-acid batteries, the content of bismuth has primary effects on the corrosion resistance of grid alloys, the composition of alloys plays an important role on batteries performance, and appropriate scale of elements can be choosed to obtain optimal electrochemical performance. The lead-acid batteries using this kind of grid show good performance by cycle life test.
