The conversion of CO_(2) into specific aromatics by modulating the morphology of zeolites is a promising strategy.HZSM-5 zeolite with hollow tubular morphology is reported.The morphology of zeolite was precisely contr...The conversion of CO_(2) into specific aromatics by modulating the morphology of zeolites is a promising strategy.HZSM-5 zeolite with hollow tubular morphology is reported.The morphology of zeolite was precisely controlled,and the acid sites on its outer surface were passivated by steam-assisted crystallization method,so that the zeolite exhibits higher aromatic selectivity than sheet HZSM-5 zeolite and greater p-xylene selectivity than chain HZSM-5 zeolite.The tandem catalyst was formed by combining hollow tubular HZSM-5 zeolites with ZnZrO_(x)metal oxides.The para-selectivity of p-xylene reached 76.2%at reaction temperature of 320℃,pressure of 3.0 MPa,and a flow rate of 2400 mL g^(-1)h^(-1)with an H_(2)/CO_(2) molar ratio of 3/1.Further research indicates that the high selectivity of p-xylene is due to the pore structure of hollow tubular HZSM-5 zeolite,which is conducive to the formation of p-xylene.Moreover,the passivation of the acid site located on the outer surface of zeolite effectively prevents the isomerization of p-xylene.The reaction mechanism of CO_(2) hydrogenation over the tandem catalyst was investigated using in-situ diffuse reflectance Fourier transform infrared spectroscopy and density functional theory.The results showed that the CO_(2) to p-xylene followed a methanol-mediated route over ZnZrO_(x)/hollow tubular HZSM-5 tandem catalysts.In addition,the catalyst showed no significant deactivation in the 100 h stability test.This present study provides an effective strategy for the design of catalysts aimed at selectively preparing aromatics through CO_(2)hydrogenation.展开更多
The effect of Ti3C2 MXene nanosheets on the intumescent flame retardant(IFR)poly(lactic acid)(PLA)composites was investigated among a series of PLA/IFR/MXene,which were prepared by melt blending 0-2.0 wt%MXene,10.0 wt...The effect of Ti3C2 MXene nanosheets on the intumescent flame retardant(IFR)poly(lactic acid)(PLA)composites was investigated among a series of PLA/IFR/MXene,which were prepared by melt blending 0-2.0 wt%MXene,10.0 wt%-12.0 wt%IFR and PLA together.The results of limiting oxygen index(LOI)and vertical burning(UL-94)discover that the combination of 0.5 wt%MXene and 11.5 wt%IFR synergistically improves the fire safety of PLA to reach UL-94 V-0 rating with LOI value of 33.0%.The PLA/IFR/MXene composites perform an obvious reduction in peak of heat release rate(HRR)in cone calorimeter tests(CCTs).Furthermore,the carbon residues after CCTs were characterized by scanning electron microscope(SEM),laser Raman spectroscopy(LRS),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).It is demonstrated that both the titanium composition of the MXene structure and the characteristics of the two-dimensional material enhance the PLA/IFR/MXene composite materials’ability to produce a dense barrier layer to resist burnout during thermal degradation.展开更多
Metal halide perovskite(MHP)quantum dots(QDs)offer immense potentialfor several areas of photonics research due to their easy and low-costfabrication and excellent optoelectronic properties.However,practicalapplicatio...Metal halide perovskite(MHP)quantum dots(QDs)offer immense potentialfor several areas of photonics research due to their easy and low-costfabrication and excellent optoelectronic properties.However,practicalapplications of MHP QDs are limited by their poor stability and,in particular,their tendency to aggregate.Here,we develop a two-step double-solventstrategy to grow and confine CsPbBr_(3)QDs within the three-dimensional(3D)cavities of a mesoporous SBA-16 silica scaffold(CsPbBr_(3)@SBA-16).Strongconfinement and separation of the MHP QDs lead to a relatively uniform sizedistribution,narrow luminescence,and good ambient stability over 2 months.In addition,the CsPbBr_(3)@SBA-16 presents a high activity and stability forvisible-light-driven photocatalytic toluene C(sp^(3))-H bond activation toproduce benzaldehyde with~730 umolg^(-1)h^(-l) yield rate and near-unityselectivity.Similarly,the structural stability of CsPbBr_(3)@SBA-16QDs issuperior to that of both pure CsPbBr3 QDs and those confined in MCM-41with 1D channels.展开更多
CdZnS solid solutions with strong light absorption are promising materials for solar-driven COreduction;however,their relatively weak redox ability and intrinsic photo-corrosion limit their further development as a ph...CdZnS solid solutions with strong light absorption are promising materials for solar-driven COreduction;however,their relatively weak redox ability and intrinsic photo-corrosion limit their further development as a photocatalyst.The addition of a second photocatalyst with a suitable band structure to construct a S-scheme photocatalytic system can solve both problems simultaneously.Here,we report a S-scheme photocatalyst based on the heterostructure of CoTiO_(3)/CdZnS(abbreviated as CoTiO_(3)/Cd_(9.51)Zn_(0.49)S_(10))that enables the efficient photocatalytic reduction of CO.Detailed physicochemical characterization resolves the S-scheme charge transfer mechanism in this composite photocatalyst.With the well-designed structure of particles and desirable band offsets,this hybrid system offers visible light absorption in a broad spectral region,large surface area,strong redox ability,and fast carrier separation and transportation.Under visible-light illumination,the CoTiO_(3)/Cd Zn S hybrid system displays a CO formation rate of about 11 mmol hgcombined with a long-term operational stability.Besides,a high apparent quantum efficiency(AQE)of 7.27%is realized for the CO_(2)-to-CO reduction reaction by the optimized Co TiO/Cd Zn S hybrid under 420 nm monochromatic light irradiation.展开更多
In this article,graphene oxide(GO)and benzotriazole-loaded mesoporous silica nanoparticles(BTA/MSNs)are combined on micro scale through the in situ polymerization of polydopamine(PDA),preparing a selfhealing bi-functi...In this article,graphene oxide(GO)and benzotriazole-loaded mesoporous silica nanoparticles(BTA/MSNs)are combined on micro scale through the in situ polymerization of polydopamine(PDA),preparing a selfhealing bi-functional GO(fGO)used as nano-fillers for anti-corrosion enhancement of waterborne epoxy(WEP)coatings.Scanning electronic microscopy(SEM)images show that the BTA/MSNs are uniformly distributed on the surface of high aspect ratio GO nanosheets to endow GO nanocontainer characteristics.UV-vis profiles demonstrate that fGO has p H-controlled release function.Modulus at lowest frequency is generally used for comparing the corrosion resistance of organic coatings.Modulus at lowest frequency(1.42×10^(5)Ωcm^(2))after 30 days immersion in 3.5 wt.%Na Cl solution revealed 2 orders of magnitude higher that of blank WEP(1.17×10^(7)Ωcm^(2)).With artificial cracks on its coatings,fGO/WEP had no obvious rust compared with blank WEP after 240 h of immersion.We anticipate that self-healing and physical barrier bi-functional nanocontainers improve the traditional anticorrosion coating efficiency with better,longer-lasting performance for shipping,oil drilling or bridge maintenance.展开更多
In this paper, vibration reduction of a flexible marine riser with time-varying internal fluid is studied by using boundary control method and Lyapunov＇s direct method. To achieve more accurate and practical riser＇s...In this paper, vibration reduction of a flexible marine riser with time-varying internal fluid is studied by using boundary control method and Lyapunov＇s direct method. To achieve more accurate and practical riser＇s dynamic behavior, the model of marine riser with time-varying internal fluid is modeled by a distributed parameter system （DPS） with partial differential equations （PDEs） and ordinary differential equations （ODEs） involving functions of space and time. The dynamic responses of riser are completely different if the time-varying internal fluid is considered. Boundary control is designed at the top boundary of the riser based on original infinite dimensionality PDEs model and Lyapunov＇s direct method to reduce the riser＇s vibrations. The uniform boundedness and closed-loop stability are proved based on the proposed boundary control. Simulation results verify the effectiveness of the proposed boundary control.展开更多
Ultrasmall gold(Au)clusters have been regarded as one of the prototypes materials for solar energy conversion due to their unique strong molecular-like light absorption properties.However,the light-induced aggregation...Ultrasmall gold(Au)clusters have been regarded as one of the prototypes materials for solar energy conversion due to their unique strong molecular-like light absorption properties.However,the light-induced aggregation of Au clusters into nanoparticles is one of the most important factors that restricts its application in photocatalysis.Although Au clusters aggregation has been widely demonstrated,the underlying mechanism for cluster fusion is still unclear due to the lack of experimental evidence.Herein,we report the direct observation of Au clusters on TiO_(2) nanosheets aggregating when used as visible light photocatalysts for the reduction of nitroaromatics.Through in situ high-resolution transmission electron microscopy(TEM),the coexistence of two fusion mechanisms of Au clusters on TiO_(2) under ultraviolet-visible(UV-Vis)light irradiation in air is identified,i.e.,the migration and coalescence(MC)and Ostwald ripening(OR).Additionally,the correlation between the photostability of Au clusters and reaction atmospheres has been investigated,among which Au clusters have higher stability in an inert N_(2) atmosphere or vacuum than the oxidizing atmospheres(i.e.,air and O_(2)).These results indicate the inherent stability of Au cluster during photocatalysis,and instability comes from the consuming of ligand layer.This work not only discloses the underlying mechanism of Au cluster sintering but also provides guidelines for enhancing metal clusters-based photocatalysts stability.展开更多
基金financially supported by the National Natural Science Foundation of China(22268039)the Natural Science Foundation for Distinguished Young Scholars of Gansu Province(23JRRA682)。
文摘The conversion of CO_(2) into specific aromatics by modulating the morphology of zeolites is a promising strategy.HZSM-5 zeolite with hollow tubular morphology is reported.The morphology of zeolite was precisely controlled,and the acid sites on its outer surface were passivated by steam-assisted crystallization method,so that the zeolite exhibits higher aromatic selectivity than sheet HZSM-5 zeolite and greater p-xylene selectivity than chain HZSM-5 zeolite.The tandem catalyst was formed by combining hollow tubular HZSM-5 zeolites with ZnZrO_(x)metal oxides.The para-selectivity of p-xylene reached 76.2%at reaction temperature of 320℃,pressure of 3.0 MPa,and a flow rate of 2400 mL g^(-1)h^(-1)with an H_(2)/CO_(2) molar ratio of 3/1.Further research indicates that the high selectivity of p-xylene is due to the pore structure of hollow tubular HZSM-5 zeolite,which is conducive to the formation of p-xylene.Moreover,the passivation of the acid site located on the outer surface of zeolite effectively prevents the isomerization of p-xylene.The reaction mechanism of CO_(2) hydrogenation over the tandem catalyst was investigated using in-situ diffuse reflectance Fourier transform infrared spectroscopy and density functional theory.The results showed that the CO_(2) to p-xylene followed a methanol-mediated route over ZnZrO_(x)/hollow tubular HZSM-5 tandem catalysts.In addition,the catalyst showed no significant deactivation in the 100 h stability test.This present study provides an effective strategy for the design of catalysts aimed at selectively preparing aromatics through CO_(2)hydrogenation.
基金support from the National Natural Science Foundation of China(Grant Nos.21908031 and 51903092)the China Postdoctoral Science Foundation funded project(Grant No.2019M652884)support from Guangdong Special Support Program(Grant No.2017TX04N371)。
文摘The effect of Ti3C2 MXene nanosheets on the intumescent flame retardant(IFR)poly(lactic acid)(PLA)composites was investigated among a series of PLA/IFR/MXene,which were prepared by melt blending 0-2.0 wt%MXene,10.0 wt%-12.0 wt%IFR and PLA together.The results of limiting oxygen index(LOI)and vertical burning(UL-94)discover that the combination of 0.5 wt%MXene and 11.5 wt%IFR synergistically improves the fire safety of PLA to reach UL-94 V-0 rating with LOI value of 33.0%.The PLA/IFR/MXene composites perform an obvious reduction in peak of heat release rate(HRR)in cone calorimeter tests(CCTs).Furthermore,the carbon residues after CCTs were characterized by scanning electron microscope(SEM),laser Raman spectroscopy(LRS),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).It is demonstrated that both the titanium composition of the MXene structure and the characteristics of the two-dimensional material enhance the PLA/IFR/MXene composite materials’ability to produce a dense barrier layer to resist burnout during thermal degradation.
基金Research Foundation—Flanders,Grant/Award Numbers:1242922N,1280021N,12Y7221N,V400622NFlemishgovernment for iBOF funding,Grant/Award Number:PERsist:iBOF-21-085+2 种基金KU Leuven Research Fund,Grant/A ward Number:C14/23/090China Scholarship Council(CSC),Grant/Award Number:201806650002Australian Research Council,Grant/Award Number:DE230100173。
文摘Metal halide perovskite(MHP)quantum dots(QDs)offer immense potentialfor several areas of photonics research due to their easy and low-costfabrication and excellent optoelectronic properties.However,practicalapplications of MHP QDs are limited by their poor stability and,in particular,their tendency to aggregate.Here,we develop a two-step double-solventstrategy to grow and confine CsPbBr_(3)QDs within the three-dimensional(3D)cavities of a mesoporous SBA-16 silica scaffold(CsPbBr_(3)@SBA-16).Strongconfinement and separation of the MHP QDs lead to a relatively uniform sizedistribution,narrow luminescence,and good ambient stability over 2 months.In addition,the CsPbBr_(3)@SBA-16 presents a high activity and stability forvisible-light-driven photocatalytic toluene C(sp^(3))-H bond activation toproduce benzaldehyde with~730 umolg^(-1)h^(-l) yield rate and near-unityselectivity.Similarly,the structural stability of CsPbBr_(3)@SBA-16QDs issuperior to that of both pure CsPbBr3 QDs and those confined in MCM-41with 1D channels.
基金the National Key R&D Program of China(2021YFA1502100)NSFC(Grants Nos.21773031,22011530144,U1805255)+3 种基金Natural Science Foundation of Fujian Province of China(2018J01686)the State Key Laboratory of NBC Protection for Civilian(SKLNBC2020-18)Graphene Powder&Composite Research Center of Fujian Province(2017H2001)financial support from the Research Foundation,Flanders(FWO Grant No.VS052320N)。
文摘CdZnS solid solutions with strong light absorption are promising materials for solar-driven COreduction;however,their relatively weak redox ability and intrinsic photo-corrosion limit their further development as a photocatalyst.The addition of a second photocatalyst with a suitable band structure to construct a S-scheme photocatalytic system can solve both problems simultaneously.Here,we report a S-scheme photocatalyst based on the heterostructure of CoTiO_(3)/CdZnS(abbreviated as CoTiO_(3)/Cd_(9.51)Zn_(0.49)S_(10))that enables the efficient photocatalytic reduction of CO.Detailed physicochemical characterization resolves the S-scheme charge transfer mechanism in this composite photocatalyst.With the well-designed structure of particles and desirable band offsets,this hybrid system offers visible light absorption in a broad spectral region,large surface area,strong redox ability,and fast carrier separation and transportation.Under visible-light illumination,the CoTiO_(3)/Cd Zn S hybrid system displays a CO formation rate of about 11 mmol hgcombined with a long-term operational stability.Besides,a high apparent quantum efficiency(AQE)of 7.27%is realized for the CO_(2)-to-CO reduction reaction by the optimized Co TiO/Cd Zn S hybrid under 420 nm monochromatic light irradiation.
基金supported by the National Natural Science Foundation of China(Grant No.51908031)the China Scholarship Council for a graduate fellowship(201906150013)+2 种基金the support from Guangdong Special Support Program(Grant No.2017TX04N371)ERC Enercapsule project(647969)Royal Society project IECR2202163。
文摘In this article,graphene oxide(GO)and benzotriazole-loaded mesoporous silica nanoparticles(BTA/MSNs)are combined on micro scale through the in situ polymerization of polydopamine(PDA),preparing a selfhealing bi-functional GO(fGO)used as nano-fillers for anti-corrosion enhancement of waterborne epoxy(WEP)coatings.Scanning electronic microscopy(SEM)images show that the BTA/MSNs are uniformly distributed on the surface of high aspect ratio GO nanosheets to endow GO nanocontainer characteristics.UV-vis profiles demonstrate that fGO has p H-controlled release function.Modulus at lowest frequency is generally used for comparing the corrosion resistance of organic coatings.Modulus at lowest frequency(1.42×10^(5)Ωcm^(2))after 30 days immersion in 3.5 wt.%Na Cl solution revealed 2 orders of magnitude higher that of blank WEP(1.17×10^(7)Ωcm^(2)).With artificial cracks on its coatings,fGO/WEP had no obvious rust compared with blank WEP after 240 h of immersion.We anticipate that self-healing and physical barrier bi-functional nanocontainers improve the traditional anticorrosion coating efficiency with better,longer-lasting performance for shipping,oil drilling or bridge maintenance.
基金supported by the National Natural Science Foundation of China(No.61203060)the Natural Science Foundation of Guangdong Province(No.S2011040005707)+2 种基金the Specialized Research Fund for the Doctoral Program of Higher Education(No.20120172120033)the Fundamental Research Funds for the Central Universities of SCUT(No.2011ZZ0020)the Special Funds for Safety Production of Guangdong Province(No.2010-95)
文摘In this paper, vibration reduction of a flexible marine riser with time-varying internal fluid is studied by using boundary control method and Lyapunov＇s direct method. To achieve more accurate and practical riser＇s dynamic behavior, the model of marine riser with time-varying internal fluid is modeled by a distributed parameter system （DPS） with partial differential equations （PDEs） and ordinary differential equations （ODEs） involving functions of space and time. The dynamic responses of riser are completely different if the time-varying internal fluid is considered. Boundary control is designed at the top boundary of the riser based on original infinite dimensionality PDEs model and Lyapunov＇s direct method to reduce the riser＇s vibrations. The uniform boundedness and closed-loop stability are proved based on the proposed boundary control. Simulation results verify the effectiveness of the proposed boundary control.
基金supported by the National Natural Science Foundation of China(Nos.21902132,91934303,21390391,21473193,21673198,and 21621091)the Award Program for Minjiang Scholar Professorship,the National Key Research and Development Program of China(No.2017YFA0206500)+2 种基金the European Union’s Horizon 2020 research and innovation programme under the Marie Sktodowska-Curie grant agreement No.891276,Research Foundation-Flanders(FWO,No.128002IN)the KU Leuven Research Fund(C14/15/053 and C14/19/079)the European Union(Horizon 2020)Marie Sklodowska-Curie innovation program(No.722591).
文摘Ultrasmall gold(Au)clusters have been regarded as one of the prototypes materials for solar energy conversion due to their unique strong molecular-like light absorption properties.However,the light-induced aggregation of Au clusters into nanoparticles is one of the most important factors that restricts its application in photocatalysis.Although Au clusters aggregation has been widely demonstrated,the underlying mechanism for cluster fusion is still unclear due to the lack of experimental evidence.Herein,we report the direct observation of Au clusters on TiO_(2) nanosheets aggregating when used as visible light photocatalysts for the reduction of nitroaromatics.Through in situ high-resolution transmission electron microscopy(TEM),the coexistence of two fusion mechanisms of Au clusters on TiO_(2) under ultraviolet-visible(UV-Vis)light irradiation in air is identified,i.e.,the migration and coalescence(MC)and Ostwald ripening(OR).Additionally,the correlation between the photostability of Au clusters and reaction atmospheres has been investigated,among which Au clusters have higher stability in an inert N_(2) atmosphere or vacuum than the oxidizing atmospheres(i.e.,air and O_(2)).These results indicate the inherent stability of Au cluster during photocatalysis,and instability comes from the consuming of ligand layer.This work not only discloses the underlying mechanism of Au cluster sintering but also provides guidelines for enhancing metal clusters-based photocatalysts stability.
