The helium turbine expander,a pivotal component within a hydrogen liquefaction system,is crucial for effective cooling.Through the use of a multistage series-connected turbine expander,the system is able to accommodat...The helium turbine expander,a pivotal component within a hydrogen liquefaction system,is crucial for effective cooling.Through the use of a multistage series-connected turbine expander,the system is able to accommodate more complex operating conditions and provide enhanced refrigeration efficiency by a gradual and controlled reduction in temperature,thereby optimizing overall performance.In this study,the interstage characteristics of a two-stage series-connected helium turbine expander in a hydrogen liquefaction system employing the inverse Brayton cycle are analyzed in depth.After validation of the reliability of the numerical simulation results using a rigorous on-site joint test system incorporating the helium turbine expander,the operational performance of each expander stage and that of the second-stage expander under various operating conditions are obtained.In addition,the energy loss distributions within various through-flow components and the primary loss zones within the impeller are comprehensively analyzed on the basis of entropy production theory.The findings presented in this paper represent a significant contribution in providing a foundational reference for the development of multistage series-connected cryogenic gas turbine expanders.展开更多
The synthesis of superior-quality zeolite nanoassemblies remains a critical objective,driven by their potential to significantly enhance mass transfer and improve accessibility to active sites,ultimately leading to en...The synthesis of superior-quality zeolite nanoassemblies remains a critical objective,driven by their potential to significantly enhance mass transfer and improve accessibility to active sites,ultimately leading to enhanced catalytic performance.In this study,we report the facile synthesis of a unique class of ZSM-5 nanorod assem-blies,referred to as NA-ZSM-5,through a straightforward approach that combines a Silicalite-1(Sil-1)seed-induced strategy with the assistance of cetyltrimethylammonium bromide(CTAB).Notably,each bundle-shaped zeolite crystal exhibits an abundance of inter-nano-crystal mesopores,comprising numerous loosely stacked nanorods,thereby displaying distinctive anisotropic characteristics.Moreover,the size of the nanorods can be easily adjusted by changing the amount of CTAB added.The morphological progression of the ZSM-5 nanorod assemblies was comprehensively investigated using a range of analytical techniques.Our analysis reveals that the incorporation of Sil-1 seeds into the synthesis process plays a pivotal role in establishing the primary framework structure,facilitating the attachment of precursor particles and promoting the creation of nucleation sites crucial for nanorod growth.In contrast,CTAB primarily acts as a modulating agent,influencing the c-axis-oriented growth of the nanorods.The resulting NA-ZSM-5 zeolite demonstrates a substantial surface area,contains specific mesoporous structures,and exhibits moderate acidity,all of which contribute to its outstanding catalytic performance in the alkylation of benzene with ethanol.Remarkably,this catalyst displays remarkable reaction stability,withstanding continuous operation for over 500 hours,even under con-ditions characterized by a low benzene/ethanol ratio of 2.展开更多
Herein,a cocatalyst was extensively used to enhance the photocatalytic water oxidation performance.In a cocatalyst/semiconductor system,charge transfer between a semiconductor and cocatalyst is a crucial process for t...Herein,a cocatalyst was extensively used to enhance the photocatalytic water oxidation performance.In a cocatalyst/semiconductor system,charge transfer between a semiconductor and cocatalyst is a crucial process for the photoelectrochemical(PEC)water oxidation performance;however,the influence of surface states on charge transfer has rarely been discussed.In this study,Al_(2)O_(3)was inserted into the CoPi/Ti-Fe_(2)O_(3)interface to fabricate a CoPi/Al_(2)O_(3)/Ti-Fe_(2)O_(3)photoanode.CoPi/Al_(2)O_(3)/Ti-Fe_(2)O_(3)showed a notable improvement in the photocurrent density.A combination of UV-vis diffuse reflectance spectroscopy(DRS),surface photovoltage spectroscopy(SPS),chopped light photocurrent,and photocurrents under different chopped light frequencies was used to study the real role of Al_(2)O_(3)in the charge transfer process.It was found that Al_(2)O_(3)passivated the surface states of Ti-doped Fe_(2)O_(3),leading to a better interfacial charge transfer between Ti-doped Fe_(2)O_(3)and CoPi,resulting in the enhanced PEC water oxidation performance.展开更多
In this work,a new design of ternary core-shell nanostructures of Au@ZnO-Pd was demonstrated to realize the synergetic utilization of a plasmonic effect and an electron-trapping co-catalyst for enhanced photocatalytic...In this work,a new design of ternary core-shell nanostructures of Au@ZnO-Pd was demonstrated to realize the synergetic utilization of a plasmonic effect and an electron-trapping co-catalyst for enhanced photocatalytic performance.In the ternary hybrid nanostructures,ZnO provides photo-generated carriers with higher redox ability,under UV-visible light,and Au nanocrystals perform the plasmonic hot electron injection as well as the local electromagnetic field enhancement of ZnO photoexcitation.Meanwhile,the Pd NPs can efficiently trap the generated electrons to govern the directional separation of the charge carriers.The efficient charge carrier separation in the ternary hybrid nanostructures was confirmed by steady-state PL spectra,time-resolved PL decay spectra,and transient photocurrent responses.The photocatalytic activity of the Au@ZnO-Pd nanostructures was evaluated by photodegrading phenol and methylene blue,respectively,under simulated sunlight(λ=360-780 nm),and the results showed that the Au@ZnO-Pd nanostructures gained a great enhancement of photocatalysis compared with ZnO,ZnO-Pd and Au@ZnO.Moreover,the effect of Pd loading content in the Au@ZnO-Pd nanostructures on the photocatalytic efficiency was studied within a certain range,indicating that the Au@ZnO-Pd photocatalyst with ~1.8 wt%Pd loading exhibited the best photocatalytic activities for photodegrading both phenol and methylene blue.The generation and effect of active species in the photocatalytic process were investigated using ESR testing and radical scavenging experiments.As a consequence,the integration of the ternary Au@ZnO-Pd core-shell nanostructures could achieve collective effects to greatly increase the photocatalytic efficiency.展开更多
Precise structural regulation of metal nanoclusters is critical for optimizing their catalytic performance.In this work,a core-shell copper-hydride nanocluster[Cu_(45)(C_(6)H_(11)S)_(24)(P(PhF)_(3))_(4)H_(19)]^(2+)was...Precise structural regulation of metal nanoclusters is critical for optimizing their catalytic performance.In this work,a core-shell copper-hydride nanocluster[Cu_(45)(C_(6)H_(11)S)_(24)(P(PhF)_(3))_(4)H_(19)]^(2+)was successfully synthesized via a one-pot method.Single-crystal X-ray diffraction(SCXRD),electrospray ionization mass spectrometry(ESI-MS),and X-ray photoelectron spectroscopy(XPS)were employed to characterize the nanocluster,confirming its structure consists of a Cu_(11)@Cu_(15) core encapsulated by a cage-like Cu_(19)((C_(6)H_(11)S)_(24)(P(PhF)_(3))_(4))shell,with all Cu atoms in the+1-oxidation state.Density functional theory(DFT)calculations clarified the positions of hydride atoms,electronic structure,and optical absorption properties of the nanocluster.Catalytic tests demonstrated that[Cu_(45)(C_(6)H_(11)S)_(24)(P(PhF)_(3))_(4)H_(19)]^(2+)exhibited excellent activity in the hydroboration of terminal alkynes,achieving a maximum product yield of 98.3%under optimized conditions.It also showed good compatibility with substrates bearing electron-withdrawing groups or electron-donating groups.This study bridges precise atomic-level design and catalytic application of copper nanoclusters,providing both experimental and theoretical insights for their future development in homogeneous catalysis.展开更多
基金supported by the Zhejiang Provincial Key Research and Development Project No.2023C03158.
文摘The helium turbine expander,a pivotal component within a hydrogen liquefaction system,is crucial for effective cooling.Through the use of a multistage series-connected turbine expander,the system is able to accommodate more complex operating conditions and provide enhanced refrigeration efficiency by a gradual and controlled reduction in temperature,thereby optimizing overall performance.In this study,the interstage characteristics of a two-stage series-connected helium turbine expander in a hydrogen liquefaction system employing the inverse Brayton cycle are analyzed in depth.After validation of the reliability of the numerical simulation results using a rigorous on-site joint test system incorporating the helium turbine expander,the operational performance of each expander stage and that of the second-stage expander under various operating conditions are obtained.In addition,the energy loss distributions within various through-flow components and the primary loss zones within the impeller are comprehensively analyzed on the basis of entropy production theory.The findings presented in this paper represent a significant contribution in providing a foundational reference for the development of multistage series-connected cryogenic gas turbine expanders.
基金support from the Joint Project of the Dalian University of Technology-Dalian Institute of Chemical Physics(no.HX20230236).
文摘The synthesis of superior-quality zeolite nanoassemblies remains a critical objective,driven by their potential to significantly enhance mass transfer and improve accessibility to active sites,ultimately leading to enhanced catalytic performance.In this study,we report the facile synthesis of a unique class of ZSM-5 nanorod assem-blies,referred to as NA-ZSM-5,through a straightforward approach that combines a Silicalite-1(Sil-1)seed-induced strategy with the assistance of cetyltrimethylammonium bromide(CTAB).Notably,each bundle-shaped zeolite crystal exhibits an abundance of inter-nano-crystal mesopores,comprising numerous loosely stacked nanorods,thereby displaying distinctive anisotropic characteristics.Moreover,the size of the nanorods can be easily adjusted by changing the amount of CTAB added.The morphological progression of the ZSM-5 nanorod assemblies was comprehensively investigated using a range of analytical techniques.Our analysis reveals that the incorporation of Sil-1 seeds into the synthesis process plays a pivotal role in establishing the primary framework structure,facilitating the attachment of precursor particles and promoting the creation of nucleation sites crucial for nanorod growth.In contrast,CTAB primarily acts as a modulating agent,influencing the c-axis-oriented growth of the nanorods.The resulting NA-ZSM-5 zeolite demonstrates a substantial surface area,contains specific mesoporous structures,and exhibits moderate acidity,all of which contribute to its outstanding catalytic performance in the alkylation of benzene with ethanol.Remarkably,this catalyst displays remarkable reaction stability,withstanding continuous operation for over 500 hours,even under con-ditions characterized by a low benzene/ethanol ratio of 2.
基金the National Basic Research Program of China(973 Program)(2013CB632403)the National Natural Science Foundation of China(No.51572106)the Science and Technology Developing Funding of Jilin Province(No.20150203009GX).
文摘Herein,a cocatalyst was extensively used to enhance the photocatalytic water oxidation performance.In a cocatalyst/semiconductor system,charge transfer between a semiconductor and cocatalyst is a crucial process for the photoelectrochemical(PEC)water oxidation performance;however,the influence of surface states on charge transfer has rarely been discussed.In this study,Al_(2)O_(3)was inserted into the CoPi/Ti-Fe_(2)O_(3)interface to fabricate a CoPi/Al_(2)O_(3)/Ti-Fe_(2)O_(3)photoanode.CoPi/Al_(2)O_(3)/Ti-Fe_(2)O_(3)showed a notable improvement in the photocurrent density.A combination of UV-vis diffuse reflectance spectroscopy(DRS),surface photovoltage spectroscopy(SPS),chopped light photocurrent,and photocurrents under different chopped light frequencies was used to study the real role of Al_(2)O_(3)in the charge transfer process.It was found that Al_(2)O_(3)passivated the surface states of Ti-doped Fe_(2)O_(3),leading to a better interfacial charge transfer between Ti-doped Fe_(2)O_(3)and CoPi,resulting in the enhanced PEC water oxidation performance.
基金supported by the National Natural Science Foundation of China(Grant No.21471004)the Science Foundation of Zhejiang Sci-Tech University(Grant No.17062002-Y).
文摘In this work,a new design of ternary core-shell nanostructures of Au@ZnO-Pd was demonstrated to realize the synergetic utilization of a plasmonic effect and an electron-trapping co-catalyst for enhanced photocatalytic performance.In the ternary hybrid nanostructures,ZnO provides photo-generated carriers with higher redox ability,under UV-visible light,and Au nanocrystals perform the plasmonic hot electron injection as well as the local electromagnetic field enhancement of ZnO photoexcitation.Meanwhile,the Pd NPs can efficiently trap the generated electrons to govern the directional separation of the charge carriers.The efficient charge carrier separation in the ternary hybrid nanostructures was confirmed by steady-state PL spectra,time-resolved PL decay spectra,and transient photocurrent responses.The photocatalytic activity of the Au@ZnO-Pd nanostructures was evaluated by photodegrading phenol and methylene blue,respectively,under simulated sunlight(λ=360-780 nm),and the results showed that the Au@ZnO-Pd nanostructures gained a great enhancement of photocatalysis compared with ZnO,ZnO-Pd and Au@ZnO.Moreover,the effect of Pd loading content in the Au@ZnO-Pd nanostructures on the photocatalytic efficiency was studied within a certain range,indicating that the Au@ZnO-Pd photocatalyst with ~1.8 wt%Pd loading exhibited the best photocatalytic activities for photodegrading both phenol and methylene blue.The generation and effect of active species in the photocatalytic process were investigated using ESR testing and radical scavenging experiments.As a consequence,the integration of the ternary Au@ZnO-Pd core-shell nanostructures could achieve collective effects to greatly increase the photocatalytic efficiency.
基金financial support provided by the National Natural Science Foundation of China(21901001,U24A20480,22371003)the Scientific Research Program of Anhui Province(2022AH040018)+1 种基金financial support provided by the National Natural Science Foundation of China(22203053)the Hunan Provincial Natural Science Foundation(2023JJ40606).
文摘Precise structural regulation of metal nanoclusters is critical for optimizing their catalytic performance.In this work,a core-shell copper-hydride nanocluster[Cu_(45)(C_(6)H_(11)S)_(24)(P(PhF)_(3))_(4)H_(19)]^(2+)was successfully synthesized via a one-pot method.Single-crystal X-ray diffraction(SCXRD),electrospray ionization mass spectrometry(ESI-MS),and X-ray photoelectron spectroscopy(XPS)were employed to characterize the nanocluster,confirming its structure consists of a Cu_(11)@Cu_(15) core encapsulated by a cage-like Cu_(19)((C_(6)H_(11)S)_(24)(P(PhF)_(3))_(4))shell,with all Cu atoms in the+1-oxidation state.Density functional theory(DFT)calculations clarified the positions of hydride atoms,electronic structure,and optical absorption properties of the nanocluster.Catalytic tests demonstrated that[Cu_(45)(C_(6)H_(11)S)_(24)(P(PhF)_(3))_(4)H_(19)]^(2+)exhibited excellent activity in the hydroboration of terminal alkynes,achieving a maximum product yield of 98.3%under optimized conditions.It also showed good compatibility with substrates bearing electron-withdrawing groups or electron-donating groups.This study bridges precise atomic-level design and catalytic application of copper nanoclusters,providing both experimental and theoretical insights for their future development in homogeneous catalysis.
