The effects of N-methylimidazole cation [Cnmim] with different alkyl chain lengths, the types of cations and anions of ionic liquids and the reaction parameters on the catalytic activity and the selectivity for 4,4′-...The effects of N-methylimidazole cation [Cnmim] with different alkyl chain lengths, the types of cations and anions of ionic liquids and the reaction parameters on the catalytic activity and the selectivity for 4,4′-bisphenol F were investigated. The hydrogen bonding between the hydroxyl of phenol and the C2-position hydrogen of imidazole moiety in hydrophilic imidazole-based ionic liquid has important influence on the selectivity for 4,4′-bisphenol F, and under the conditions of the molar ratio of phenol/[C4mim][HSO4] 1:1, reaction temperature65 °C and the theoretical molar ratio of phenol/formaldehyde 2:1, the selectivity for 4,4′-bisphenol F reached69.1%. Compared with the high phenol/formaldehyde ratio reported in literatures, the low molar ratio of phenol/formaldehyde and the low reaction temperature can greatly reduce energy consumption, and has important significance for industrial application.展开更多
The worst droughts in the central part of the North American Prairie in the past several hundred years have been reconstructed from tree-ring chronologies, suggesting that some drought years have exceeded the se- veri...The worst droughts in the central part of the North American Prairie in the past several hundred years have been reconstructed from tree-ring chronologies, suggesting that some drought years have exceeded the se- verity shown by the gauge record. A general circulation model of the Geophysical Fluid Dynamics Laboratory (GFDL) has simulated climate changes for the area during the past 250 years driven by c^imatic forces, providing scenarios of extreme climate that can further diagnose the mechanisms. This study refined the drought signals from the tree ring data and GFDL modeling at inter-annual and decadal time scales and analyzed the potential mecha- nisms driving the droughts. Results showed that drought years with summer precipitation Ilower than the 10th per- centiles occurred during 1777-1789, 1847-1861 and 1886-1879 AD in the area. Both tree rings and model re- vealed that the frequency of droughts has been relatively consistent in a similar timing andl frequency with climate change. Monte Carlo analysis have detected that the tree ring chronologies have recorded drought years with probabilities of 9.3%-12.8%, and the model has simulated the droughts with probabilities 5..7%-17.8%. Under CO2 and aerosol forcing, the GFDL modeled the drought recurrences of 13 years and 25 years, which are very syn- chronous changes with tree rings and consistent with gauge records. The 20-a and 10-a time scale reoccurrences of droughts are very consistent with solar radiation cycles, and similar to the length of cycles in oceanic records, suggesting that terrestrial precipitation modeling is properly driven from sun-land-sea dynamics. Detected severity, variability and return periods of droughts from the present study make potential improvements in drought predictions and constructing scenarios for climate impacts and adaptation strategies.展开更多
Halide perovskite light emitting diodes(LEDs)have gained great progress in recent years.However,mixed-halide perovskites for blue LEDs usually suffer from electroluminescence(EL)spectra shift at a high applied voltage...Halide perovskite light emitting diodes(LEDs)have gained great progress in recent years.However,mixed-halide perovskites for blue LEDs usually suffer from electroluminescence(EL)spectra shift at a high applied voltage or current density,limiting their efficiency.In this work,we report a strategy of using single-layer perovskite quantum dots(QDs)film to tackle the electroluminescence spectra shift in pure-blue perovskite LEDs and improve the LED efficiency by co-doping copper and potassium in the mixed-halide perovskite QDs.As a result,we obtained pure-blue halide perovskite QD-LEDs with stable EL spectra centred at 469 nm even at a current density of 1,617 mA·cm^(−2).The optimal device presents a maximum external quantum efficiency(EQE)of 2.0%.The average maximum EQE and luminance of the LEDs are 1.49%and 393 cd·m^(−2),increasing 62%and 66%compared with the control LEDs.Our study provides an effective strategy for achieving spectra-stable and highly efficient pure-blue perovskite LEDs.展开更多
The development of cathode oxygen reduction reaction(ORR)catalysts with high characteristics for practical,direct methanol fuel cells(DMFCs)has continuously increased the attention of researchers.In this work,interfac...The development of cathode oxygen reduction reaction(ORR)catalysts with high characteristics for practical,direct methanol fuel cells(DMFCs)has continuously increased the attention of researchers.In this work,interface-rich Au-doped PdBi(PdBiAu)branched one-dimensional(1D)alloyed nanochains assembled by sub-6.5 nm particles have been prepared,exhibiting an ORR mass activity(MA)of 6.40 A·mgPd^(−1) and long-term durability of 5,000 cycles in an alkaline medium.The MA of PdBiAu nanochains is 46 times and 80 times higher than that of commercial Pt/C(0.14 A·mgPt^(−1))and Pd/C(0.08 A·mgPd^(−1)).The MA of binary PdBi nanochains also reaches 5.71 A·mgPd^(−1).Notably,the PdBiAu nanochains exhibit high in-situ carbon monoxide poisoning resistance and high methanol tolerance.In actual DMFC device tests,the PdBiAu nanochains enhance power density of 140.1 mW·cm^(−2)(in O_(2))/112.4 mW·cm^(−2)(in air)and durability compared with PdBi nanochains and Pt/C.The analysis of the structure–function relationship indicates that the enhanced performance of PdBiAu nanochains is attributed to integrated functions of surficial defect-rich 1D chain structure,improved charge transfer capability,downshift of the d-band center of Pd,as well as the synergistic effect derived from“Pd-Bi”and/or“Pd-Au”dual active sites.展开更多
It is challenging and desirable to construct Pt-based nanocomposites with oxygen storage function as efficient oxygen reduction reaction(ORR)catalysts for practical proton exchange membrane fuel cells(PEMFCs).Herein,w...It is challenging and desirable to construct Pt-based nanocomposites with oxygen storage function as efficient oxygen reduction reaction(ORR)catalysts for practical proton exchange membrane fuel cells(PEMFCs).Herein,we achieve novel porous nanocomposites of PtCu_(3) nanoalloys-embedded in the PWO_(x) matrix(PtCu_(3)@PWO_(x)),which has an oxygen container feature.The PtCu_(3)@PWO_(x)/C exhibits an ultrahigh mass activity(MA)of 3.94 A·mgPt−1 for ORR,which is 26.3 times as high as the commercial Pt/C and the highest value ever reported for PtCu-based binary system.Theoretical calculations reveal that the compressive strain and d-band center downshift of Pt intrinsically contribute to the excellent ORR performance.In H_(2)-air PEMFCs at room temperature,furthermore,the PtCu_(3)@PWO_(x)/C delivers a high power density(218.6 mW·cm^(−2)),much superior to commercial Pt/C(131.6 mW·cm^(−2)).In H_(2)-O_(2) PEMFCs,PtCu_(3)@PWO_(x)/C outputs a maximum power density of 420.1 mW·cm^(−2).This work provides an effective idea for designing oxygen-storing ORR catalysts used for practical room-temperature H_(2)-air fuel cells.展开更多
Developing highly stable and active non-Pt oxygen reduction reaction(ORR)electrocatalysts for power generation device raises great concerns and remains a challenge.Here,we report novel truncated Pd tetrahedrons(T-Pd-T...Developing highly stable and active non-Pt oxygen reduction reaction(ORR)electrocatalysts for power generation device raises great concerns and remains a challenge.Here,we report novel truncated Pd tetrahedrons(T-Pd-Ths)enclosed by{111}facets with excellent uniformity,which have both low-coordinated surface sites and distinct lattice distortions that would induce“local strain”.In alkaline electrolyte,the T-Pd-Ths/C achieves remarkable ORR specific/mass activity(SA/MA)of 2.46 mA·cm^(−2)/1.69 A·mgPd^(−1),which is 12.3/16.9 and 10.7/14.1 times higher than commercial Pd/C and Pt/C,respectively.The T-Pd-Ths/C also exhibits high in-situ carbon monoxide(CO)tolerance and 50,000 cycles durability with an activity loss of 7.69%and morphological stability.The rotating ring-disk electrode(RRDE)measurements show that a 4-electron process occurs on T-PdThs/C.Theoretical calculations demonstrate that the low-coordinated surface sites contribute largely to the enhancement of ORR activity.In actual direct methanol fuel cell(DMFC)device,the T-Pd-Ths/C delivers superior open-circuit voltage(OCV)and peak power density(PPD)to commercial Pt/C from 25 to 80℃,and the maximum PPD can reach up to 163.7 mW·cm−2.This study demonstrates that the T-Pd-Ths/C holds promise as alternatives to Pt for ORR in DMFC device.展开更多
基金Supported by the National Natural Science Foundation of China(21276217)
文摘The effects of N-methylimidazole cation [Cnmim] with different alkyl chain lengths, the types of cations and anions of ionic liquids and the reaction parameters on the catalytic activity and the selectivity for 4,4′-bisphenol F were investigated. The hydrogen bonding between the hydroxyl of phenol and the C2-position hydrogen of imidazole moiety in hydrophilic imidazole-based ionic liquid has important influence on the selectivity for 4,4′-bisphenol F, and under the conditions of the molar ratio of phenol/[C4mim][HSO4] 1:1, reaction temperature65 °C and the theoretical molar ratio of phenol/formaldehyde 2:1, the selectivity for 4,4′-bisphenol F reached69.1%. Compared with the high phenol/formaldehyde ratio reported in literatures, the low molar ratio of phenol/formaldehyde and the low reaction temperature can greatly reduce energy consumption, and has important significance for industrial application.
基金Financial support for this work was provided by Global Change Research Program of the Ministry of Science and Technology of China (2012CB956103)International Partnership Program and External Cooperation Program of the Chinese Academy of Sciences (KZZD-EW-TZ-08,GJHZ1214)Key Directional Program of the Chinese Academy of Sciences (KZCX2-YW-338-2)
文摘The worst droughts in the central part of the North American Prairie in the past several hundred years have been reconstructed from tree-ring chronologies, suggesting that some drought years have exceeded the se- verity shown by the gauge record. A general circulation model of the Geophysical Fluid Dynamics Laboratory (GFDL) has simulated climate changes for the area during the past 250 years driven by c^imatic forces, providing scenarios of extreme climate that can further diagnose the mechanisms. This study refined the drought signals from the tree ring data and GFDL modeling at inter-annual and decadal time scales and analyzed the potential mecha- nisms driving the droughts. Results showed that drought years with summer precipitation Ilower than the 10th per- centiles occurred during 1777-1789, 1847-1861 and 1886-1879 AD in the area. Both tree rings and model re- vealed that the frequency of droughts has been relatively consistent in a similar timing andl frequency with climate change. Monte Carlo analysis have detected that the tree ring chronologies have recorded drought years with probabilities of 9.3%-12.8%, and the model has simulated the droughts with probabilities 5..7%-17.8%. Under CO2 and aerosol forcing, the GFDL modeled the drought recurrences of 13 years and 25 years, which are very syn- chronous changes with tree rings and consistent with gauge records. The 20-a and 10-a time scale reoccurrences of droughts are very consistent with solar radiation cycles, and similar to the length of cycles in oceanic records, suggesting that terrestrial precipitation modeling is properly driven from sun-land-sea dynamics. Detected severity, variability and return periods of droughts from the present study make potential improvements in drought predictions and constructing scenarios for climate impacts and adaptation strategies.
基金the National Natural Science Foundation of China(Nos.52102188 and 52072337)the Key Research and Development Program of Zhejiang Province(No.2021C01030)+4 种基金the Natural Science Foundation of Zhejiang Province(No.LQ21F040005)the Postdoctoral Science Foundation of Zhejiang Province(No.ZJ2022132)the Science and Technology Project of Wenzhou(No.2022G0253)the Leading Talent Entrepreneurship Project of Ouhai District,Wenzhou City,the Young Elite Scientists Sponsorship Program by CAST(No.YESS20210444)the Shanxi‐Zheda Institute of Advanced Materials and Chemical Engineering(No.2022SZ‐TD004).
文摘Halide perovskite light emitting diodes(LEDs)have gained great progress in recent years.However,mixed-halide perovskites for blue LEDs usually suffer from electroluminescence(EL)spectra shift at a high applied voltage or current density,limiting their efficiency.In this work,we report a strategy of using single-layer perovskite quantum dots(QDs)film to tackle the electroluminescence spectra shift in pure-blue perovskite LEDs and improve the LED efficiency by co-doping copper and potassium in the mixed-halide perovskite QDs.As a result,we obtained pure-blue halide perovskite QD-LEDs with stable EL spectra centred at 469 nm even at a current density of 1,617 mA·cm^(−2).The optimal device presents a maximum external quantum efficiency(EQE)of 2.0%.The average maximum EQE and luminance of the LEDs are 1.49%and 393 cd·m^(−2),increasing 62%and 66%compared with the control LEDs.Our study provides an effective strategy for achieving spectra-stable and highly efficient pure-blue perovskite LEDs.
基金supported by the National Natural Science Foundation of China(No.21571038)Foundation of Guizhou Province(No.2019-5666)+3 种基金Education Department of Guizhou Province(No.2021312)State Key Laboratory of Coal Mine Disaster Dynamics and Control(Chongqing University,No.2011DA105287-ZR202101)the Open Fund of the Key Lab of Organic Optoelectronics&Molecular Engineering(Tsinghua University)State Key Laboratory of Physical Chemistry of Solid Surfaces(No.202009).
文摘The development of cathode oxygen reduction reaction(ORR)catalysts with high characteristics for practical,direct methanol fuel cells(DMFCs)has continuously increased the attention of researchers.In this work,interface-rich Au-doped PdBi(PdBiAu)branched one-dimensional(1D)alloyed nanochains assembled by sub-6.5 nm particles have been prepared,exhibiting an ORR mass activity(MA)of 6.40 A·mgPd^(−1) and long-term durability of 5,000 cycles in an alkaline medium.The MA of PdBiAu nanochains is 46 times and 80 times higher than that of commercial Pt/C(0.14 A·mgPt^(−1))and Pd/C(0.08 A·mgPd^(−1)).The MA of binary PdBi nanochains also reaches 5.71 A·mgPd^(−1).Notably,the PdBiAu nanochains exhibit high in-situ carbon monoxide poisoning resistance and high methanol tolerance.In actual DMFC device tests,the PdBiAu nanochains enhance power density of 140.1 mW·cm^(−2)(in O_(2))/112.4 mW·cm^(−2)(in air)and durability compared with PdBi nanochains and Pt/C.The analysis of the structure–function relationship indicates that the enhanced performance of PdBiAu nanochains is attributed to integrated functions of surficial defect-rich 1D chain structure,improved charge transfer capability,downshift of the d-band center of Pd,as well as the synergistic effect derived from“Pd-Bi”and/or“Pd-Au”dual active sites.
基金supported by the National Natural Science Foundation of China(42288201,41725014,and 41888101)the State Key Laboratory of Lithospheric Evolution(SKL-Z202302)the China Geological Survey Project(DD20190098).
基金supported by the National Natural Science Foundation of China(No.21571038)Foundation of Guizhou Province(No.2019-5666)+3 种基金Education Department of Guizhou Province(No.2021312)State Key Laboratory of Coal Mine Disaster Dynamics and Control(Chongqing University,No.2011DA105287-ZR202101)State Key Laboratory of Physica Chemistry of Solid Surfaces(Xiamen University,No.202009)the Open Fund of the Key Lab of Organic Optoelectronics&Molecular Engineering(Tsinghua University).
文摘It is challenging and desirable to construct Pt-based nanocomposites with oxygen storage function as efficient oxygen reduction reaction(ORR)catalysts for practical proton exchange membrane fuel cells(PEMFCs).Herein,we achieve novel porous nanocomposites of PtCu_(3) nanoalloys-embedded in the PWO_(x) matrix(PtCu_(3)@PWO_(x)),which has an oxygen container feature.The PtCu_(3)@PWO_(x)/C exhibits an ultrahigh mass activity(MA)of 3.94 A·mgPt−1 for ORR,which is 26.3 times as high as the commercial Pt/C and the highest value ever reported for PtCu-based binary system.Theoretical calculations reveal that the compressive strain and d-band center downshift of Pt intrinsically contribute to the excellent ORR performance.In H_(2)-air PEMFCs at room temperature,furthermore,the PtCu_(3)@PWO_(x)/C delivers a high power density(218.6 mW·cm^(−2)),much superior to commercial Pt/C(131.6 mW·cm^(−2)).In H_(2)-O_(2) PEMFCs,PtCu_(3)@PWO_(x)/C outputs a maximum power density of 420.1 mW·cm^(−2).This work provides an effective idea for designing oxygen-storing ORR catalysts used for practical room-temperature H_(2)-air fuel cells.
基金the National Natural Science Foundation of China(No.21571038)Education Department of Guizhou Province(No.2021312)+4 种基金Foundation of Guizhou Province(No.2019-5666)Science Foundation for Aftergraduated Students of Guizhou Province(No.YJSCXJH2020045)State Key Laboratory of Coal Mine Disaster Dynamics and Control(Chongqing University,No.2011DA105287-ZR202101)State Key Laboratory of Physical Chemistry of Solid Surfaces(Xiamen University,No.202009)the Open Fund of the Key Lab of Organic Optoelectronics&Molecular Engineering(Tsinghua University)。
文摘Developing highly stable and active non-Pt oxygen reduction reaction(ORR)electrocatalysts for power generation device raises great concerns and remains a challenge.Here,we report novel truncated Pd tetrahedrons(T-Pd-Ths)enclosed by{111}facets with excellent uniformity,which have both low-coordinated surface sites and distinct lattice distortions that would induce“local strain”.In alkaline electrolyte,the T-Pd-Ths/C achieves remarkable ORR specific/mass activity(SA/MA)of 2.46 mA·cm^(−2)/1.69 A·mgPd^(−1),which is 12.3/16.9 and 10.7/14.1 times higher than commercial Pd/C and Pt/C,respectively.The T-Pd-Ths/C also exhibits high in-situ carbon monoxide(CO)tolerance and 50,000 cycles durability with an activity loss of 7.69%and morphological stability.The rotating ring-disk electrode(RRDE)measurements show that a 4-electron process occurs on T-PdThs/C.Theoretical calculations demonstrate that the low-coordinated surface sites contribute largely to the enhancement of ORR activity.In actual direct methanol fuel cell(DMFC)device,the T-Pd-Ths/C delivers superior open-circuit voltage(OCV)and peak power density(PPD)to commercial Pt/C from 25 to 80℃,and the maximum PPD can reach up to 163.7 mW·cm−2.This study demonstrates that the T-Pd-Ths/C holds promise as alternatives to Pt for ORR in DMFC device.