Supercritical fluids play a crucial role in material transport within Earth's deep interior.Investigating the pressure-dependent atomic structures and transport properties of such fluids is essential for understan...Supercritical fluids play a crucial role in material transport within Earth's deep interior.Investigating the pressure-dependent atomic structures and transport properties of such fluids is essential for understanding their petrological,chemical,and geophysical behaviors.In this study,we employed first-principles molecular dynamics simulations to explore the structures,self-diffusion coefficients(D),and viscosities(η)of supercritical NaAlSi_(3)O_(8)-H_(2)O fluids under conditions of 2000 K and 3-10 GPa,with water contents of 30 wt% and 50 wt%.Our calculations indicate that at a water content of 30 wt%,Q^(2) and Q^(3) exhibit a certain degree of positive and negative pressure dependence,respectively,while other Q^(n) species(n represents the number of bridging oxygens connected to Si/Al)show minimal changes.At a water content of 50 wt%,Q^(2) and Q^(0) exhibit a certain degree of positive and negative pressure dependence,respectively,while other Q^(n) species show minimal changes.At both water contents,Si-O-H and molecular water in the system exhibit negative pressure dependence,suggesting that the migration of supercritical fluids from deep to shallow regions is accompanied by the release of water.The self-diffusion coefficients in the supercritical NaAlSi_(3)O_(8)-H_(2)O fluid follow the order D_(Na)≈D_(H)>D_(O)>D_(Al)≈D_(Si),with an overall weak negative pressure dependence.By comparing the viscosities of anhydrous and hydrous silicate melts from previous studies,we found that the addition of water caused a transition from negative to positive pressure dependence of viscosity,corresponding to a structural change from polymerization to depolymerization.Additionally,we calculated the fluid mobility Δp/η of supercritical NaAlSi_(3)O_(8)-H_(2)O fluids and found that their mobility is several orders of magnitude higher than that of basalt melt and is also significantly greater than that of carbonate melt.As supercritical fluids ascend from deeper to shallower regions,their mobility is further enhanced,significantly contributing to the transport of elements from subducting slabs to the overlying mantle wedge.展开更多
The rapid recombination of photogenerated carriers poses a significant limitation on the use of CdS quantum dots(QDs)in photocatalysis.Herein,the construction of a novel S-scheme heterojunction between cubic-phase CdS...The rapid recombination of photogenerated carriers poses a significant limitation on the use of CdS quantum dots(QDs)in photocatalysis.Herein,the construction of a novel S-scheme heterojunction between cubic-phase CdS QDs and hollow nanotube In_(2)O_(3)is successfully achieved using an electrostatic self-assembly method.Under visible light irradiation,all CdS-In_(2)O_(3)composites exhibit higher hydrogen evolution efficiency compared to pure CdS QDs.Notably,the photocatalytic H_(2)evolution rate of the optimal CdS-7%In_(2)O_(3)composite is determined to be 2258.59μmol g^(−1)h^(−1),approximately 12.3 times higher than that of pure CdS.The cyclic test indicates that the CdS-In_(2)O_(3)composite maintains considerable activity even after 5 cycles,indicating its excellent stability.In situ X-ray photoelectron spectroscopy and density functional theory calculations confirm that carrier migration in CdS-In_(2)O_(3)composites adheres to a typical S-scheme heterojunction mechanism.Additionally,a series of characterizations demonstrate that the formation of S-scheme heterojunctions between In_(2)O_(3)and CdS inhibits charge recombination and accelerates the separation and migration of photogenerated carriers in the CdS QDs,thus achieving enhanced photocatalytic performance.This work elucidates the pivotal role of S-scheme heterojunctions in photocatalytic H_(2)production and offers novel insights into the construction of effective composite photocatalysts.展开更多
Ti-10V-2Fe-3Al alloy with fine-grainedβphases was fabricated by friction stir processing with opti-mized processing parameters.The superplastic behavior of the specimens was investigated by tensile deformation at dif...Ti-10V-2Fe-3Al alloy with fine-grainedβphases was fabricated by friction stir processing with opti-mized processing parameters.The superplastic behavior of the specimens was investigated by tensile deformation at different strain rates and temperatures,and an optimal superplastic elongation of 634%was achieved at 700℃ and 3×10^(-4)/s.An annealing treatment at 650℃ for 60 min showed a mi-crostructure withαprecipitates distributed in theβmatrix in the friction stir specimen.Such pre-heat treatment improves the superplasticity of the specimen,achieving an elongation of up to 807%at 750℃ and 3×10^(-4)/s.The influences of tensile temperatures and strain rates on the microstructural evolution,such as grain size variation,grain morphology,and phase transformations,were discussed.The super-plastic deformation behavior of fine-grained Ti-10V-2Fe-3Al alloy is controlled by grain boundary sliding and accompanied by dynamic phase transformation and recrystallization.展开更多
Electrochromic(EC)smart windows utilizing a reversible metal electrodeposition device(RMED)offer a compelling alternative for dynamically regulating transmissions of optical and thermal energy.An EC device(ECD)is cons...Electrochromic(EC)smart windows utilizing a reversible metal electrodeposition device(RMED)offer a compelling alternative for dynamically regulating transmissions of optical and thermal energy.An EC device(ECD)is constructed by reversible metal electrodeposition(RME)of Bi/Cu on WO_(3)·xH_(2)O film electrodeposited onto fluorine-doped tin oxide(FTO)transparent conductive glass.The electrolyte consists of CuCl_(2),BiCl_(3),KCl and HCl aqueous solution,supplying necessary components for both electrochemical and electrodeposition processes.The ECD shows ability to rapidly transition between colorless and black states,which achieves a large optical modulation of 77.0%at 570 nm.In the black state,the ECD exhibits a near-zero transmittance in the wavelength range of 400-1100 nm while maintaining 96.6%of its initial optical modulation after coloration/bleaching cycling of 60000 s,exhibiting good cyclic stability.This RMED has relatively high stability under open-circuit voltage and also possesses excellent heat insulation performance.The results offer a solution to overcome the poor cyclic stability of RMEDs and improve the optical modulation of ECDs.展开更多
P2型层状过渡金属氧化物(P2-Na_(x)TMO_(2))因其优异的循环稳定性和倍率性能,成为钠离子电池正极材料的有力候选者。然而,其在高电压下的不可逆相变和固有低理论容量问题,阻碍了实际应用。本研究工作提出高熵策略与双相结构的协同设计...P2型层状过渡金属氧化物(P2-Na_(x)TMO_(2))因其优异的循环稳定性和倍率性能,成为钠离子电池正极材料的有力候选者。然而,其在高电压下的不可逆相变和固有低理论容量问题,阻碍了实际应用。本研究工作提出高熵策略与双相结构的协同设计来克服这些挑战。通过在P2相高熵基体中引入O3相,构建新型P2/O3双相高熵层状氧化物Na_(0.70)Ni_(0.25)Mn_(0.35)Co_(0.15)Fe_(0.05)Ti_(0.20)O_(2)(简称Na_(0.70)NMCFT)。其中,高熵设计通过构型熵稳定效应有效抑制P2相的不可逆相变,而O3相则通过协同作用弥补容量不足并提升循环稳定性。此外,双相组分之间的相互作用进一步促进P2-O3与P2-P3相变的高度可逆性。Na_(0.70)NMCFT在1C倍率下的初始放电容量为102.08 mAhg^(-1),200次循环后容量保持率达88.15%,表明具有优异的循环稳定性。更重要的是,即使在10C的高倍率下,Na_(0.70)NMCFT仍能提供85.67 mAh g^(-1)的初始放电比容量,并在1000次循环后容量保持率达70%。本工作证实双相高熵设计在提升钠离子电池正极性能中的关键作用,为开发先进钠离子电池正极材料提供了新思路。展开更多
Herein,we established a Zn_(3)(OH)_(2)(V_(2)O_(7))(H_(2)O)_(2)/V-Zn(O,S)Z-scheme heterojunction labeled ZnVO/V-Zn(O,S)with a heterovalent V^(4+)/V^(5+)states and oxygen vacancies in both phases via a one-step in-situ ...Herein,we established a Zn_(3)(OH)_(2)(V_(2)O_(7))(H_(2)O)_(2)/V-Zn(O,S)Z-scheme heterojunction labeled ZnVO/V-Zn(O,S)with a heterovalent V^(4+)/V^(5+)states and oxygen vacancies in both phases via a one-step in-situ hydrolysis method.The NaBH_(4) regulated the ZnVO/V-Zn(O,S)-3 with rich Vo and suitable n(V^(4+))/n(V^(5+))ratio achieved an excellent photocatalytic nitrogen fixation activity of 301.7μmol/(g×h)and apparent quantum efficiency of 1.148%at 420 nm without any sacrificial agent,which is 11 times than that of V-Zn(O,S).The Vo acts as the active site to trap and activate N_(2) molecules and to trap and activate H_(2)O to produce the H for N_(2) molecules photocatalytic reduction.The rich Vo defects can also reduce the competitive adsorption of H_(2)O and N_(2) molecules on the surface active site of the catalyst.The heterovalent vanadium states act as the photogenerated electrons,quickly hopping between V^(4+)and V^(5+)to transfer for the photocatalytic N_(2) reduction reaction.Additionally,the Z-scheme heterojunction effectively minimizes photogenerated carrier recombination.These synergistic effects collectively boost the photocatalytic nitrogen fixation activity.This study provides a practical method for designing Z-scheme heterojunctions for efficient photocatalytic N_(2) fixation under mild conditions.展开更多
After the hot deformation sample of Ti-10V-2Fe-3Al alloy was treated by solid solution in theα+βtwo-phase region,the coarseβgrains that often appeared in theβsingle phase region were observed in the local region,i...After the hot deformation sample of Ti-10V-2Fe-3Al alloy was treated by solid solution in theα+βtwo-phase region,the coarseβgrains that often appeared in theβsingle phase region were observed in the local region,indicating that the abnormal grain growth occurred in the local microstructural region,and the macrostructure also showed abnormally coarse grains(ACGs).The dynamic recrystallization(DRX)behavior of Ti-10V-2Fe-3Al titanium alloy was systematically investigated through hot compression tests on the Gleeble-3800 system.The DRX model ofβgrains was established,and the quantitative correlation between DRX characteristics and the appearance of ACG was clarified.Based on these results,a numerical simulation platform was developed to realize the visual prediction of ACG distribution.The results show that the increase of deformation temperature and the decrease of strain rate both contribute to a significant increase in the grain size(d_(DRX)))and volume fraction(X_(DRX))of DRXed grains.However,the proper X_(DRX)and smaller d_(DRX))at low deformation temperature and high strain rate make the macro and microstructure show ACGs after solid solution.Interestingly,if the DRX degree is excessive or insufficient,ACGs cannot be produced,indicating that ACGs are solid solution products based on the appropriate DRX degree.According to the flow curves and statistical results of microstructure,the quantitative model of DRX kinetics and DRX grain size model were constructed,and the quantitative criterion model that is related to the formation of ACG with grain size(d_(DRX)))and volume fraction(X_(DRX))of DRXed grains as the key parameters was established,i.e.,d_(DRX)≤2.60µm,72.5%≤X_(DRX)≤87.9%.By integrating the subroutine of coarse grain criterion,the isothermal compression process of cylindrical samples and the actual die forging process of H-shaped parts were simulated by DEFORM-3D software of finite element(FE),respectively,and the visual prediction of the distribution of macroscopic ACGs was realized.There is a good consistency between the tested results and the simulated results,indicating a strong correlation between macroscopic ACGs and microscopic DRX.展开更多
In this work,the TiO_(2)/Sb_(2)S_(3) nanorod arrays(NRAs)were synthesized through a two-stage hydrothermal route for photoelectrochemical(PEC)water splitting.The effect of annealing treatment in Ar ambience on the PEC...In this work,the TiO_(2)/Sb_(2)S_(3) nanorod arrays(NRAs)were synthesized through a two-stage hydrothermal route for photoelectrochemical(PEC)water splitting.The effect of annealing treatment in Ar ambience on the PEC activity of TiO_(2)/Sb_(2)S_(3) composite sample was investigated by electrochemical impedance analysis,including Nyquist and Mott-Schottky(M-S)plots.It was demonstrated that vacuum annealing could crystallize Sb_(2)S_(3) component and change its color from red to black,leading to an increment of photocurrent density from 1.9 A/m^(2) to 4.25 A/m^(2) at 0 V versus saturated calomel electrode(VSCE).The enhanced PEC performance was mainly attributed to the improved visible light absorption.Moreover,annealing treatment facilitated retarding the electron-hole recombination occurred at the solid/liquid interfaces.Our work might provide a novel strategy for enhancing the PEC performance of a semiconductor electrode.展开更多
The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO_(2) from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonizatio...The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO_(2) from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonization.However,steelwork off-gases typically contain various impurities,including H_(2)S,which can deactivate commercial methanol synthesis catalysts,Cu/ZnO/Al_(2)O_(3)(CZA).Reverse water-gas shift(RWGS)reaction is the predominant side reaction in CO_(2) hydrogenation to methanol which can occur at ambient pressure,enabling the decouple of RWGS from methanol production at high pressure.Then,a series of activated CZA catalysts has been in-situ pretreated in 400 ppm H_(2)S/Ar at 250℃and tested for both RWGS reaction at ambient pressure and CO_(2) hydrogenation to methanol at high pressure.An innovative decoupling strategy was employed to isolate the RWGS reaction from the methanol synthesis process,enabling the investigation of the evolution of active site structures and the poisoning mechanism through elemental analysis,X-ray Diffraction,X-ray Photoelectron Spectroscopy,Fourier Transform Infrared Spectroscopy,Temperature Programmed Reduction and CO_(2) Temperature Programmed Desorption.The results indicate that there are different dynamic migration behaviors of ZnO_(x) in the two reaction systems,leading to different poisoning mechanisms.These interesting findings are beneficial to develop sulfur resistant and durable highly efficient catalysts for CO_(2) hydrogenation to methanol,promoting the carbon emission reduction in steel industry.展开更多
β-Sialon has emerged as a promising material for enhancing the service life of Al_(2)O_(3)-C refractories due to its excellent physicochemical properties.The impact of varying concentrations of nanometer Al/Si alloy ...β-Sialon has emerged as a promising material for enhancing the service life of Al_(2)O_(3)-C refractories due to its excellent physicochemical properties.The impact of varying concentrations of nanometer Al/Si alloy on the in-situ synthesis of β-Sialon within Al_(2)O_(3)-C refractory materials,as well as its oxidation behavior,was investigated.The findings indicate that the presence of Al/Si alloy promotes the formation of AlN and SiC whiskers at 1300℃,which subsequently facilitate the production of plate-like β-Sialon at 1500℃.Density functional theory analysis reveals that the(020)crystal plane of β-Sialon exhibits the lowest adsorption energy for Al2O and AlO molecules under the influence of iron atoms,suggesting a solid-liquid-vapor growth mechanism for β-Sialon formation.The introduction of these ceramic phases significantly enhances the mechanical properties of Al_(2)O_(3)-C refractories.Specifically,the addition of 6 wt.%Al/Si alloy yielded specimens with the highest cold modulus of rupture and cold crushing strength at 1500℃,achieving values of 35.2 and 127.5 MPa,respectively--representing increases of 40.1%and 37.4%.Furthermore,during high-temperature oxidation,the formation of plate-like β-Sialon leads to the development of a dense protective layer on the surface.This impedes the diffusion pathways of oxygen and consequently enhances the oxidation resistance of the refractory.展开更多
Ammonia Selective Catalytic Reduction(NHs-SCR)technology has been employed to eliminate NO_(x) from diesel engine exhaust,with Cu-SSZ-13 serving as the commercial catalyst.The greenhouse gas N_(2)O is produced as a by...Ammonia Selective Catalytic Reduction(NHs-SCR)technology has been employed to eliminate NO_(x) from diesel engine exhaust,with Cu-SSZ-13 serving as the commercial catalyst.The greenhouse gas N_(2)O is produced as a byproduct when using Cu-SSZ-13 as the NH_(3)-SCR catalyst.To achieve synergistic control of pollutants and greenhouse gases in diesel engine exhaust,rational design of Cu-SSZ-13 catalysts is required.In this study,the effect of Brønsted acid sites in Cu-SSZ-13 catalysts on the formation of N_(2)O was investigated.Mild thermal treatmentwas innovatively employed to prepare Cu-SSZ-13 catalysts with different amounts of Brønsted acid sites.EPR,H_(2)-TPR,NH_(3)-TPD,NMR were utilized to determine that the Brønsted acid sites were modified while the Cu species remained unchanged.Thereby an accurate assessment of the influence of Brønsted acid sites on N_(2)O formation could be achieved.Our results showed that Cu-SSZ-13 with more Brønsted acid sites produced less N_(2)O during the NH_(3)-SCR reaction.In the low-temperature region,the presence of framework acid sites facilitates the decomposition of the NH_(4)NO_(3)assisted by NO to form N_(2)and H_(2)O,reducing the formation of N_(2)O.In the high-temperature region,the Brønsted acid sites promote the decomposition of NH_(2)NO into N_(2)and H_(2)O.Meanwhile,the N_(2)O-SCR reaction can also be promoted by Brønsted acid sites,thereby decreasing N_(2)O emissions.This study suggests that in the future design and synthesis of Cu-SSZ-13 zeolites,attention should be paid to creating more Brønsted acid sites in Cu-SSZ-13 to reduce N_(2)O emissions.展开更多
基金funded by National Natural Science Foundation of China(42373033,Yicheng Sun)Fundamental Research Funds for the Central Universities(B240201111,Yicheng Sun)。
文摘Supercritical fluids play a crucial role in material transport within Earth's deep interior.Investigating the pressure-dependent atomic structures and transport properties of such fluids is essential for understanding their petrological,chemical,and geophysical behaviors.In this study,we employed first-principles molecular dynamics simulations to explore the structures,self-diffusion coefficients(D),and viscosities(η)of supercritical NaAlSi_(3)O_(8)-H_(2)O fluids under conditions of 2000 K and 3-10 GPa,with water contents of 30 wt% and 50 wt%.Our calculations indicate that at a water content of 30 wt%,Q^(2) and Q^(3) exhibit a certain degree of positive and negative pressure dependence,respectively,while other Q^(n) species(n represents the number of bridging oxygens connected to Si/Al)show minimal changes.At a water content of 50 wt%,Q^(2) and Q^(0) exhibit a certain degree of positive and negative pressure dependence,respectively,while other Q^(n) species show minimal changes.At both water contents,Si-O-H and molecular water in the system exhibit negative pressure dependence,suggesting that the migration of supercritical fluids from deep to shallow regions is accompanied by the release of water.The self-diffusion coefficients in the supercritical NaAlSi_(3)O_(8)-H_(2)O fluid follow the order D_(Na)≈D_(H)>D_(O)>D_(Al)≈D_(Si),with an overall weak negative pressure dependence.By comparing the viscosities of anhydrous and hydrous silicate melts from previous studies,we found that the addition of water caused a transition from negative to positive pressure dependence of viscosity,corresponding to a structural change from polymerization to depolymerization.Additionally,we calculated the fluid mobility Δp/η of supercritical NaAlSi_(3)O_(8)-H_(2)O fluids and found that their mobility is several orders of magnitude higher than that of basalt melt and is also significantly greater than that of carbonate melt.As supercritical fluids ascend from deeper to shallower regions,their mobility is further enhanced,significantly contributing to the transport of elements from subducting slabs to the overlying mantle wedge.
文摘The rapid recombination of photogenerated carriers poses a significant limitation on the use of CdS quantum dots(QDs)in photocatalysis.Herein,the construction of a novel S-scheme heterojunction between cubic-phase CdS QDs and hollow nanotube In_(2)O_(3)is successfully achieved using an electrostatic self-assembly method.Under visible light irradiation,all CdS-In_(2)O_(3)composites exhibit higher hydrogen evolution efficiency compared to pure CdS QDs.Notably,the photocatalytic H_(2)evolution rate of the optimal CdS-7%In_(2)O_(3)composite is determined to be 2258.59μmol g^(−1)h^(−1),approximately 12.3 times higher than that of pure CdS.The cyclic test indicates that the CdS-In_(2)O_(3)composite maintains considerable activity even after 5 cycles,indicating its excellent stability.In situ X-ray photoelectron spectroscopy and density functional theory calculations confirm that carrier migration in CdS-In_(2)O_(3)composites adheres to a typical S-scheme heterojunction mechanism.Additionally,a series of characterizations demonstrate that the formation of S-scheme heterojunctions between In_(2)O_(3)and CdS inhibits charge recombination and accelerates the separation and migration of photogenerated carriers in the CdS QDs,thus achieving enhanced photocatalytic performance.This work elucidates the pivotal role of S-scheme heterojunctions in photocatalytic H_(2)production and offers novel insights into the construction of effective composite photocatalysts.
基金financially supported by the National Natural Science Foundation of China(No.52105373)the China Scholarship Council(No.202106020094).
文摘Ti-10V-2Fe-3Al alloy with fine-grainedβphases was fabricated by friction stir processing with opti-mized processing parameters.The superplastic behavior of the specimens was investigated by tensile deformation at different strain rates and temperatures,and an optimal superplastic elongation of 634%was achieved at 700℃ and 3×10^(-4)/s.An annealing treatment at 650℃ for 60 min showed a mi-crostructure withαprecipitates distributed in theβmatrix in the friction stir specimen.Such pre-heat treatment improves the superplasticity of the specimen,achieving an elongation of up to 807%at 750℃ and 3×10^(-4)/s.The influences of tensile temperatures and strain rates on the microstructural evolution,such as grain size variation,grain morphology,and phase transformations,were discussed.The super-plastic deformation behavior of fine-grained Ti-10V-2Fe-3Al alloy is controlled by grain boundary sliding and accompanied by dynamic phase transformation and recrystallization.
文摘Electrochromic(EC)smart windows utilizing a reversible metal electrodeposition device(RMED)offer a compelling alternative for dynamically regulating transmissions of optical and thermal energy.An EC device(ECD)is constructed by reversible metal electrodeposition(RME)of Bi/Cu on WO_(3)·xH_(2)O film electrodeposited onto fluorine-doped tin oxide(FTO)transparent conductive glass.The electrolyte consists of CuCl_(2),BiCl_(3),KCl and HCl aqueous solution,supplying necessary components for both electrochemical and electrodeposition processes.The ECD shows ability to rapidly transition between colorless and black states,which achieves a large optical modulation of 77.0%at 570 nm.In the black state,the ECD exhibits a near-zero transmittance in the wavelength range of 400-1100 nm while maintaining 96.6%of its initial optical modulation after coloration/bleaching cycling of 60000 s,exhibiting good cyclic stability.This RMED has relatively high stability under open-circuit voltage and also possesses excellent heat insulation performance.The results offer a solution to overcome the poor cyclic stability of RMEDs and improve the optical modulation of ECDs.
文摘P2型层状过渡金属氧化物(P2-Na_(x)TMO_(2))因其优异的循环稳定性和倍率性能,成为钠离子电池正极材料的有力候选者。然而,其在高电压下的不可逆相变和固有低理论容量问题,阻碍了实际应用。本研究工作提出高熵策略与双相结构的协同设计来克服这些挑战。通过在P2相高熵基体中引入O3相,构建新型P2/O3双相高熵层状氧化物Na_(0.70)Ni_(0.25)Mn_(0.35)Co_(0.15)Fe_(0.05)Ti_(0.20)O_(2)(简称Na_(0.70)NMCFT)。其中,高熵设计通过构型熵稳定效应有效抑制P2相的不可逆相变,而O3相则通过协同作用弥补容量不足并提升循环稳定性。此外,双相组分之间的相互作用进一步促进P2-O3与P2-P3相变的高度可逆性。Na_(0.70)NMCFT在1C倍率下的初始放电容量为102.08 mAhg^(-1),200次循环后容量保持率达88.15%,表明具有优异的循环稳定性。更重要的是,即使在10C的高倍率下,Na_(0.70)NMCFT仍能提供85.67 mAh g^(-1)的初始放电比容量,并在1000次循环后容量保持率达70%。本工作证实双相高熵设计在提升钠离子电池正极性能中的关键作用,为开发先进钠离子电池正极材料提供了新思路。
文摘Herein,we established a Zn_(3)(OH)_(2)(V_(2)O_(7))(H_(2)O)_(2)/V-Zn(O,S)Z-scheme heterojunction labeled ZnVO/V-Zn(O,S)with a heterovalent V^(4+)/V^(5+)states and oxygen vacancies in both phases via a one-step in-situ hydrolysis method.The NaBH_(4) regulated the ZnVO/V-Zn(O,S)-3 with rich Vo and suitable n(V^(4+))/n(V^(5+))ratio achieved an excellent photocatalytic nitrogen fixation activity of 301.7μmol/(g×h)and apparent quantum efficiency of 1.148%at 420 nm without any sacrificial agent,which is 11 times than that of V-Zn(O,S).The Vo acts as the active site to trap and activate N_(2) molecules and to trap and activate H_(2)O to produce the H for N_(2) molecules photocatalytic reduction.The rich Vo defects can also reduce the competitive adsorption of H_(2)O and N_(2) molecules on the surface active site of the catalyst.The heterovalent vanadium states act as the photogenerated electrons,quickly hopping between V^(4+)and V^(5+)to transfer for the photocatalytic N_(2) reduction reaction.Additionally,the Z-scheme heterojunction effectively minimizes photogenerated carrier recombination.These synergistic effects collectively boost the photocatalytic nitrogen fixation activity.This study provides a practical method for designing Z-scheme heterojunctions for efficient photocatalytic N_(2) fixation under mild conditions.
基金Projects(52275388,52075474)supported by the National Natural Science Foundation of ChinaProject(236Z1008G)supported by the Special Project of Hebei Provincial Central Government Guiding Local Science and Technology Development,China+1 种基金Project(E2022203206)supported by the Natural Science Foundation of Hebei Province,ChinaProject(241080457A)supported by the Shijiazhuang's University-Industry-Academia Cooperation Project in Hebei Province-Major Science and Technology Special Project,China。
文摘After the hot deformation sample of Ti-10V-2Fe-3Al alloy was treated by solid solution in theα+βtwo-phase region,the coarseβgrains that often appeared in theβsingle phase region were observed in the local region,indicating that the abnormal grain growth occurred in the local microstructural region,and the macrostructure also showed abnormally coarse grains(ACGs).The dynamic recrystallization(DRX)behavior of Ti-10V-2Fe-3Al titanium alloy was systematically investigated through hot compression tests on the Gleeble-3800 system.The DRX model ofβgrains was established,and the quantitative correlation between DRX characteristics and the appearance of ACG was clarified.Based on these results,a numerical simulation platform was developed to realize the visual prediction of ACG distribution.The results show that the increase of deformation temperature and the decrease of strain rate both contribute to a significant increase in the grain size(d_(DRX)))and volume fraction(X_(DRX))of DRXed grains.However,the proper X_(DRX)and smaller d_(DRX))at low deformation temperature and high strain rate make the macro and microstructure show ACGs after solid solution.Interestingly,if the DRX degree is excessive or insufficient,ACGs cannot be produced,indicating that ACGs are solid solution products based on the appropriate DRX degree.According to the flow curves and statistical results of microstructure,the quantitative model of DRX kinetics and DRX grain size model were constructed,and the quantitative criterion model that is related to the formation of ACG with grain size(d_(DRX)))and volume fraction(X_(DRX))of DRXed grains as the key parameters was established,i.e.,d_(DRX)≤2.60µm,72.5%≤X_(DRX)≤87.9%.By integrating the subroutine of coarse grain criterion,the isothermal compression process of cylindrical samples and the actual die forging process of H-shaped parts were simulated by DEFORM-3D software of finite element(FE),respectively,and the visual prediction of the distribution of macroscopic ACGs was realized.There is a good consistency between the tested results and the simulated results,indicating a strong correlation between macroscopic ACGs and microscopic DRX.
基金supported by the Fundamental Research Funds for the Central Universities(No.2019ZDPY04).
文摘In this work,the TiO_(2)/Sb_(2)S_(3) nanorod arrays(NRAs)were synthesized through a two-stage hydrothermal route for photoelectrochemical(PEC)water splitting.The effect of annealing treatment in Ar ambience on the PEC activity of TiO_(2)/Sb_(2)S_(3) composite sample was investigated by electrochemical impedance analysis,including Nyquist and Mott-Schottky(M-S)plots.It was demonstrated that vacuum annealing could crystallize Sb_(2)S_(3) component and change its color from red to black,leading to an increment of photocurrent density from 1.9 A/m^(2) to 4.25 A/m^(2) at 0 V versus saturated calomel electrode(VSCE).The enhanced PEC performance was mainly attributed to the improved visible light absorption.Moreover,annealing treatment facilitated retarding the electron-hole recombination occurred at the solid/liquid interfaces.Our work might provide a novel strategy for enhancing the PEC performance of a semiconductor electrode.
基金supported by the National Natural Science Foundation of China(Nos.22276060 and 21976059)Guangdong Basic and Applied Basic Research Foundation(No.2024A1515012636)China Scholarship Council Scholarship(No.201906155006)。
文摘The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO_(2) from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonization.However,steelwork off-gases typically contain various impurities,including H_(2)S,which can deactivate commercial methanol synthesis catalysts,Cu/ZnO/Al_(2)O_(3)(CZA).Reverse water-gas shift(RWGS)reaction is the predominant side reaction in CO_(2) hydrogenation to methanol which can occur at ambient pressure,enabling the decouple of RWGS from methanol production at high pressure.Then,a series of activated CZA catalysts has been in-situ pretreated in 400 ppm H_(2)S/Ar at 250℃and tested for both RWGS reaction at ambient pressure and CO_(2) hydrogenation to methanol at high pressure.An innovative decoupling strategy was employed to isolate the RWGS reaction from the methanol synthesis process,enabling the investigation of the evolution of active site structures and the poisoning mechanism through elemental analysis,X-ray Diffraction,X-ray Photoelectron Spectroscopy,Fourier Transform Infrared Spectroscopy,Temperature Programmed Reduction and CO_(2) Temperature Programmed Desorption.The results indicate that there are different dynamic migration behaviors of ZnO_(x) in the two reaction systems,leading to different poisoning mechanisms.These interesting findings are beneficial to develop sulfur resistant and durable highly efficient catalysts for CO_(2) hydrogenation to methanol,promoting the carbon emission reduction in steel industry.
基金supported by the Natural Science Foundation of Henan Province(No.232300420329)Key Scientific Research Project of Colleges and Universities in Henan Province(Nos.23B430012,22A430028,and 25B430022)+2 种基金Henan Provincial Science and Technology Research Project(No.242102231064)National Natural Science Foundation of China(No.52202064)Luoyang Major Science and Technology Innovation Project(No.2301009A).
文摘β-Sialon has emerged as a promising material for enhancing the service life of Al_(2)O_(3)-C refractories due to its excellent physicochemical properties.The impact of varying concentrations of nanometer Al/Si alloy on the in-situ synthesis of β-Sialon within Al_(2)O_(3)-C refractory materials,as well as its oxidation behavior,was investigated.The findings indicate that the presence of Al/Si alloy promotes the formation of AlN and SiC whiskers at 1300℃,which subsequently facilitate the production of plate-like β-Sialon at 1500℃.Density functional theory analysis reveals that the(020)crystal plane of β-Sialon exhibits the lowest adsorption energy for Al2O and AlO molecules under the influence of iron atoms,suggesting a solid-liquid-vapor growth mechanism for β-Sialon formation.The introduction of these ceramic phases significantly enhances the mechanical properties of Al_(2)O_(3)-C refractories.Specifically,the addition of 6 wt.%Al/Si alloy yielded specimens with the highest cold modulus of rupture and cold crushing strength at 1500℃,achieving values of 35.2 and 127.5 MPa,respectively--representing increases of 40.1%and 37.4%.Furthermore,during high-temperature oxidation,the formation of plate-like β-Sialon leads to the development of a dense protective layer on the surface.This impedes the diffusion pathways of oxygen and consequently enhances the oxidation resistance of the refractory.
基金supported by the National Key R&D Program of China(Nos.2023YFC3707200 and 2022YFC3704400)the National Natural Science Foundation of China(Nos.52200136,22402220,and 52225004)Hangzhou Qianjiang Distinguished Experts Project.
文摘Ammonia Selective Catalytic Reduction(NHs-SCR)technology has been employed to eliminate NO_(x) from diesel engine exhaust,with Cu-SSZ-13 serving as the commercial catalyst.The greenhouse gas N_(2)O is produced as a byproduct when using Cu-SSZ-13 as the NH_(3)-SCR catalyst.To achieve synergistic control of pollutants and greenhouse gases in diesel engine exhaust,rational design of Cu-SSZ-13 catalysts is required.In this study,the effect of Brønsted acid sites in Cu-SSZ-13 catalysts on the formation of N_(2)O was investigated.Mild thermal treatmentwas innovatively employed to prepare Cu-SSZ-13 catalysts with different amounts of Brønsted acid sites.EPR,H_(2)-TPR,NH_(3)-TPD,NMR were utilized to determine that the Brønsted acid sites were modified while the Cu species remained unchanged.Thereby an accurate assessment of the influence of Brønsted acid sites on N_(2)O formation could be achieved.Our results showed that Cu-SSZ-13 with more Brønsted acid sites produced less N_(2)O during the NH_(3)-SCR reaction.In the low-temperature region,the presence of framework acid sites facilitates the decomposition of the NH_(4)NO_(3)assisted by NO to form N_(2)and H_(2)O,reducing the formation of N_(2)O.In the high-temperature region,the Brønsted acid sites promote the decomposition of NH_(2)NO into N_(2)and H_(2)O.Meanwhile,the N_(2)O-SCR reaction can also be promoted by Brønsted acid sites,thereby decreasing N_(2)O emissions.This study suggests that in the future design and synthesis of Cu-SSZ-13 zeolites,attention should be paid to creating more Brønsted acid sites in Cu-SSZ-13 to reduce N_(2)O emissions.
