Quaternary chalcogenides are viewed as a class of potential thermoelectric materials due to their good thermoelectric performance in the medium temperature region.In this work,carbon nanotubes(CNTs)with varying weight...Quaternary chalcogenides are viewed as a class of potential thermoelectric materials due to their good thermoelectric performance in the medium temperature region.In this work,carbon nanotubes(CNTs)with varying weight percentages are composited into the quaternary chalcogenide Cu_(2.1)Mn_(0.9)SnSe_(4)(CMTS)using a technique that combines ball-milling and hot-pressing,and the effect of CNTs on the thermoelectric performance of CMTS is investigated.The compositing of CNTs results in an increase in the intrinsic defects of CMTS,thereby enhancing the electrical conductivities of the composited samples.Besides,the addition of CNTs introduces various phonon scattering mechanisms,effectively restraining the lattice thermal conductivities of the composited samples,particularly in the low to medium temperature range.Ultimately,owing to the concurrent optimization of the power factor and thermal conductivity,the x=0.25 sample achieves a zT value of 0.37 at 673 K.The compositing of highly conductive secondary phase is recognized as a viable approach for the simultaneous enhancement of the thermoelectric properties of materials.展开更多
The intrinsic low lattice thermal conductivities originates from the complex anion bonding environment make quaternary chalcogenides potential thermoelectric materials.Here,the bonding environment of Se atom in Cu_(2....The intrinsic low lattice thermal conductivities originates from the complex anion bonding environment make quaternary chalcogenides potential thermoelectric materials.Here,the bonding environment of Se atom in Cu_(2.1)Mn_(0.9)SnSe_(4)is further regulated by substituting Mn^(2+)with equimolar pairing elements(Agt and In^(3+)).The increase in both bond length and angle,together with the reduction in bond strength of AgeSe and IneSe bonds,cause the doped samples to display strong anharmonicities(γ~1.84-2.04).And the weakened bond strength also lower the sound velocities.Consequently,the kL of the doped samples is effectively constrained,achieving a minimum value of 0.55 W·m^(-1)·K^(-1)at 673 K in x=0.10 sample.Ultimately,a zT value of 0.53 at 673 K is attained in x=0.10 sample.The modification of bonding environment around anion is considered as an effective mean to optimize the thermoelectric performance of quaternary chalcogenides.展开更多
The origin of boron in the solar system has not yet been clearly understood.We studied the light mass nuclear reactions and neutrino-induced reactions that play important roles in the nucleosynthesis of A=11 nuclei in...The origin of boron in the solar system has not yet been clearly understood.We studied the light mass nuclear reactions and neutrino-induced reactions that play important roles in the nucleosynthesis of A=11 nuclei in the core-collapse supernova(CCSN).We found that the production of A=11 nuclei,particularly^(11)C,is sensitive to the radioactive nuclear reaction^(11)C(α,p)^(14)N among many others.We calculated the upper and lower limits of the^(11)C(α,p)^(14)N rate by taking account of the low energy resonances above the threshold,which have not been included in the previous SN nucleosynthesis calculations.These resonance contributions significantly change the^(11)C abundance,which decays to^(11)B with a half-life of 20.34 m,and affects the resultant isotopic abundance ratio of^(11)B/^(10)B at Mr=3.78-4.4M⊙from which the presolar X grains could form.The^(11)B/^(10)B isotopic ratio measured in X grains can help to understand the origin of solar system boron and constrain still unknown neutrino mass hierarchy if the observational and theoretical uncertainties associated with these abundances are reduced.We emphasize that the further precise experiment of measuring the^(11)C(α,p)^(14)N reaction cross sections at the astrophysically interesting energies of Gamow window 0.23-1.24 MeV,which corresponds to the effective temperature T=0.2-1 GK,could clarify CCSN contribution to the solar^(11)B/^(10)B ratio.展开更多
Renewable-energy-driven nitrate(NO_(3)^(−))electroreduction to ammonia(NH_(3))(NERA)has been an attractive technology for decarbonizing NH_(3)production and wastewater treatment.Improving NERA efficiency requires elec...Renewable-energy-driven nitrate(NO_(3)^(−))electroreduction to ammonia(NH_(3))(NERA)has been an attractive technology for decarbonizing NH_(3)production and wastewater treatment.Improving NERA efficiency requires electrocatalysts that are earth-abundant and show fantastic performance.Here we report a semiempirical activity descriptor of eg occupancy(of surface B-site cations)for identifying inexpensive perovskite oxides with extremely high efficacy toward NERA.We establish the descriptor by systematic investigations of more than 10 perovskite oxides.These investigations demonstrate that their intrinsic NERA activities display a volcano-shaped dependence on eg occupancy and the optimized intrinsic activities are accessible at near-1 eg occupancies.This could plausibly be attributed to the favorable overlaps between surface adsorbates and vertically-oriented eg orbitals.More importantly,utilizing this descriptor,we predict a highly active,selective,and durable NERA electrocatalyst with a composition of Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ)(BSCF).Because of its close-to-1 e_(g)occupancy(i.e.~1.2),the BSCF features a superior NH_(3)production rate of 0.12 g·h^(−1)·mg_(cat.)^(−1)(Faradaic efficiency of 97.8%)that is at top of the volcano plot,and substantially outperforms most NERA electrocatalysts reported in literature.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52171216 and 52472221)the Qilu Young Scholar Program of Shandong University and Core Facility Sharing Platform of Shandong University.
文摘Quaternary chalcogenides are viewed as a class of potential thermoelectric materials due to their good thermoelectric performance in the medium temperature region.In this work,carbon nanotubes(CNTs)with varying weight percentages are composited into the quaternary chalcogenide Cu_(2.1)Mn_(0.9)SnSe_(4)(CMTS)using a technique that combines ball-milling and hot-pressing,and the effect of CNTs on the thermoelectric performance of CMTS is investigated.The compositing of CNTs results in an increase in the intrinsic defects of CMTS,thereby enhancing the electrical conductivities of the composited samples.Besides,the addition of CNTs introduces various phonon scattering mechanisms,effectively restraining the lattice thermal conductivities of the composited samples,particularly in the low to medium temperature range.Ultimately,owing to the concurrent optimization of the power factor and thermal conductivity,the x=0.25 sample achieves a zT value of 0.37 at 673 K.The compositing of highly conductive secondary phase is recognized as a viable approach for the simultaneous enhancement of the thermoelectric properties of materials.
基金supported by the Natural Science Fund of China under Grant Nos.52171216 and 52472221,Qilu Young Scholar Program of Shandong University and Core Facility Sharing Platform of Shandong University.
文摘The intrinsic low lattice thermal conductivities originates from the complex anion bonding environment make quaternary chalcogenides potential thermoelectric materials.Here,the bonding environment of Se atom in Cu_(2.1)Mn_(0.9)SnSe_(4)is further regulated by substituting Mn^(2+)with equimolar pairing elements(Agt and In^(3+)).The increase in both bond length and angle,together with the reduction in bond strength of AgeSe and IneSe bonds,cause the doped samples to display strong anharmonicities(γ~1.84-2.04).And the weakened bond strength also lower the sound velocities.Consequently,the kL of the doped samples is effectively constrained,achieving a minimum value of 0.55 W·m^(-1)·K^(-1)at 673 K in x=0.10 sample.Ultimately,a zT value of 0.53 at 673 K is attained in x=0.10 sample.The modification of bonding environment around anion is considered as an effective mean to optimize the thermoelectric performance of quaternary chalcogenides.
基金under the support of CSC scholarship from the Ministry of Education of China during his stay at the National Astronomical Observatory of Japan(NAOJ)partly supported by the National Key R&D Program of China(2022YFA1602401)+1 种基金the National Natural Science Foundation of China(12335009,12435010)supported by JSPS KAKENHI(19K03883,23H01181,23K25877)from the Ministry of Education,Culture,Sports,Science and Technology(MEXT)of Japan。
文摘The origin of boron in the solar system has not yet been clearly understood.We studied the light mass nuclear reactions and neutrino-induced reactions that play important roles in the nucleosynthesis of A=11 nuclei in the core-collapse supernova(CCSN).We found that the production of A=11 nuclei,particularly^(11)C,is sensitive to the radioactive nuclear reaction^(11)C(α,p)^(14)N among many others.We calculated the upper and lower limits of the^(11)C(α,p)^(14)N rate by taking account of the low energy resonances above the threshold,which have not been included in the previous SN nucleosynthesis calculations.These resonance contributions significantly change the^(11)C abundance,which decays to^(11)B with a half-life of 20.34 m,and affects the resultant isotopic abundance ratio of^(11)B/^(10)B at Mr=3.78-4.4M⊙from which the presolar X grains could form.The^(11)B/^(10)B isotopic ratio measured in X grains can help to understand the origin of solar system boron and constrain still unknown neutrino mass hierarchy if the observational and theoretical uncertainties associated with these abundances are reduced.We emphasize that the further precise experiment of measuring the^(11)C(α,p)^(14)N reaction cross sections at the astrophysically interesting energies of Gamow window 0.23-1.24 MeV,which corresponds to the effective temperature T=0.2-1 GK,could clarify CCSN contribution to the solar^(11)B/^(10)B ratio.
基金the National Natural Science Foundation of China(No.52102258)the Taishan Scholars Program(No.tsqn202306309)+2 种基金Natural Science Foundation of Shandong Province(No.ZR2023YQ012)Natural Science Foundation of Jiangsu Province(No.BK20210447)the Special Fund Project of Jiangsu Province for Scientific and Technological Innovation in Carbon Peaking and Carbon Neutrality(No.BK20220023).
文摘Renewable-energy-driven nitrate(NO_(3)^(−))electroreduction to ammonia(NH_(3))(NERA)has been an attractive technology for decarbonizing NH_(3)production and wastewater treatment.Improving NERA efficiency requires electrocatalysts that are earth-abundant and show fantastic performance.Here we report a semiempirical activity descriptor of eg occupancy(of surface B-site cations)for identifying inexpensive perovskite oxides with extremely high efficacy toward NERA.We establish the descriptor by systematic investigations of more than 10 perovskite oxides.These investigations demonstrate that their intrinsic NERA activities display a volcano-shaped dependence on eg occupancy and the optimized intrinsic activities are accessible at near-1 eg occupancies.This could plausibly be attributed to the favorable overlaps between surface adsorbates and vertically-oriented eg orbitals.More importantly,utilizing this descriptor,we predict a highly active,selective,and durable NERA electrocatalyst with a composition of Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ)(BSCF).Because of its close-to-1 e_(g)occupancy(i.e.~1.2),the BSCF features a superior NH_(3)production rate of 0.12 g·h^(−1)·mg_(cat.)^(−1)(Faradaic efficiency of 97.8%)that is at top of the volcano plot,and substantially outperforms most NERA electrocatalysts reported in literature.
