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
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
Electrolytic reduction is a crucial process during the pyroprocessing of oxide spent fuel.This paper investigates the effects of different concentrations of Li_(2)O on the properties of the LiCl^(-)UCl_(3)-Li_(2)O mol...Electrolytic reduction is a crucial process during the pyroprocessing of oxide spent fuel.This paper investigates the effects of different concentrations of Li_(2)O on the properties of the LiCl^(-)UCl_(3)-Li_(2)O molten salt system during electrolytic reduction using first-principles molecular dynamics simulations.The study reveals that increasing Li_(2)O concentration lowers the ion diffusion coefficients of Li^(+),Cl^(-),and O^(2-)in the electrolyte,which has negative effect on the transport property of the system.A thorough analysis of the ligand structures formed by various components in the molten salt was conducted,including radial distribution functions and angular distribution functions.The analysis reveals that oxygen ions compete with chloride ions for coordination with cations.This competitive interaction has a significant impact on the coordination between Li-Cl and U-Cl elements,thereby influencing the microstructure.The analysis of electronic structures shows that the addition of Li_(2)O affects the charge transfer among lithium,uranium,and chlorine,impacting the bond strength between anions and cations.Finally,the calculation of redox potential shows that an appropriate concentration of Li_(2)O is beneficial to the electrochemical reduction process.The research results provide a theoretical basis for the design of molten salts in the electrolytic reduction process.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financial support provided by the National Natural Science Foundation of China(22476130 and 12205190)。
文摘Electrolytic reduction is a crucial process during the pyroprocessing of oxide spent fuel.This paper investigates the effects of different concentrations of Li_(2)O on the properties of the LiCl^(-)UCl_(3)-Li_(2)O molten salt system during electrolytic reduction using first-principles molecular dynamics simulations.The study reveals that increasing Li_(2)O concentration lowers the ion diffusion coefficients of Li^(+),Cl^(-),and O^(2-)in the electrolyte,which has negative effect on the transport property of the system.A thorough analysis of the ligand structures formed by various components in the molten salt was conducted,including radial distribution functions and angular distribution functions.The analysis reveals that oxygen ions compete with chloride ions for coordination with cations.This competitive interaction has a significant impact on the coordination between Li-Cl and U-Cl elements,thereby influencing the microstructure.The analysis of electronic structures shows that the addition of Li_(2)O affects the charge transfer among lithium,uranium,and chlorine,impacting the bond strength between anions and cations.Finally,the calculation of redox potential shows that an appropriate concentration of Li_(2)O is beneficial to the electrochemical reduction process.The research results provide a theoretical basis for the design of molten salts in the electrolytic reduction process.
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.
