层状无机材料的弱层间耦合和大面积表面为构建低导热性无机固体材料提供了基本框架.合成具有足够散射和非谐波性的稳定层状材料,从而降低热导率,仍是一项挑战.本文在层状无机FeOCl材料体系中,通过一步氧化还原反应成功获得了一种结构稳...层状无机材料的弱层间耦合和大面积表面为构建低导热性无机固体材料提供了基本框架.合成具有足够散射和非谐波性的稳定层状材料,从而降低热导率,仍是一项挑战.本文在层状无机FeOCl材料体系中,通过一步氧化还原反应成功获得了一种结构稳定的富含Fe^(2+)的层状材料,实现了表面和界面的同步改性,并实现了超低的热导率.具体而言,系统的X射线吸收精细结构(XAFS)分析和电子能量损失光谱(EELS)分析表明,碱金属原子的层间插层和表面缺陷的引入诱导了大量Fe^(2+)的存在,从而增强了其非谐波性和声子散射.此外,声子态密度(PDOS)分布也提供了确凿的证据,证明了散射概率的提高和声子模式整体的软化.所制得的层状无机材料Fe(III)_(1−n)Fe(II)_(n)O_(1−x)Cl[K^(+)]_(m)不仅结构稳定,而且在298 K时的热导率比原始FeOCl降低了近60%,低至0.29 W m^(−1) K^(−1),这在层状无机材料中是极低的.这项研究为低导热层状材料的设计提供了新的视角.展开更多
Ta_(2)NiSe_(5)is a promising candidate for hosting an excitonic insulator(EI)phase,a novel electronic state driven by electron-hole Coulomb attraction.However,the role of electron-lattice coupling in the formation of ...Ta_(2)NiSe_(5)is a promising candidate for hosting an excitonic insulator(EI)phase,a novel electronic state driven by electron-hole Coulomb attraction.However,the role of electron-lattice coupling in the formation of the EI phase remains controversial.Here,we use angle-resolved photoemission spectroscopy(ARPES)to study the band structure evolution of Ta_(2)Ni(Se_(1-x)S_(x))_(5)with sulfur substitution and potassium deposition,which modulate the band gap and the carrier concentration,respectively.We find that the Ta 5d states originating from the bottom of the conduction band persist at the top of the valence band in the low-temperature monoclinic phase,indicating the importance of exciton condensation in opening the gap in the semi-metallic band structure.We also observe that the characteristic overlap between the conduction and valence bands can be restored in the monoclinic lattice by mild carrier injection,suggesting that the lattice distortion in the monoclinic phase is not the main factor for producing the insulating gap,but rather the exciton condensation in the electronic system is the dominant driving force.Our results shed light on the electron-lattice decoupling and the origin of the EI phase in Ta_(2)Ni(Se_(1-x)Sx)_(5).展开更多
Perovskite oxides are significant candidates to develop electrochemical catalysts for water oxidation in consideration of their high catalysis capacity,low costing and excellent stability.Rational design of coordinati...Perovskite oxides are significant candidates to develop electrochemical catalysts for water oxidation in consideration of their high catalysis capacity,low costing and excellent stability.Rational design of coordination structure and overcoming poor electronic transport are regarded as critical factors for outstanding perovskite-based oxygen evolution reaction (OER) catalysts.Herein,we report a mild chemical oxidation method to realize ligancy engineering from strongly-correlated brownmillerite Sr2Co2O5 to perovskite phase Sr2Co2O5.5,along with abundant oxygen vacancies formation and greatly boosted electric conductivity,which helps to form the active species of Co hydroxide/oxide on the surface of catalysts.The coupling effect of catalytic kinetics and unimpeded electronic movement brings high OER activities in Sr2Co2O5.5 with a low onset potential and a small Tafel slope.Our work not only displays in-depth understanding into the relationship among catalysis performance and multiple physical degrees of freedom,but also paves a new path to develop high-efficient electrochemical catalysts.展开更多
基金supported by the Chinese Academy of Sciences(CAS)Project for Young Scientists in Basic Research(YSBR-070)the National Natural Science Foundation of China(21925110,22321001 and 12147105)+5 种基金the USTC Research Funds of the Double FirstClass Initiative(YD2060002004)the National Key Research and Development Program of China(2022YFA1203600)the Anhui Provincial Key Research and Development Project(202004a050200760)the Key R&D Program of Shandong Province(2021CXGC010302)the Fellowship of China Postdoctoral Science Foundation(2022M710141)the Open Foundation of the Key Lab(Center)of Engineering Research Center of Building Energy Efficiency Control and Evaluation,Ministry of Education(AHJZNX-2023-04).
文摘层状无机材料的弱层间耦合和大面积表面为构建低导热性无机固体材料提供了基本框架.合成具有足够散射和非谐波性的稳定层状材料,从而降低热导率,仍是一项挑战.本文在层状无机FeOCl材料体系中,通过一步氧化还原反应成功获得了一种结构稳定的富含Fe^(2+)的层状材料,实现了表面和界面的同步改性,并实现了超低的热导率.具体而言,系统的X射线吸收精细结构(XAFS)分析和电子能量损失光谱(EELS)分析表明,碱金属原子的层间插层和表面缺陷的引入诱导了大量Fe^(2+)的存在,从而增强了其非谐波性和声子散射.此外,声子态密度(PDOS)分布也提供了确凿的证据,证明了散射概率的提高和声子模式整体的软化.所制得的层状无机材料Fe(III)_(1−n)Fe(II)_(n)O_(1−x)Cl[K^(+)]_(m)不仅结构稳定,而且在298 K时的热导率比原始FeOCl降低了近60%,低至0.29 W m^(−1) K^(−1),这在层状无机材料中是极低的.这项研究为低导热层状材料的设计提供了新的视角.
基金financially supported by the National Key R&D Program on Nano Science&Technology of the MOST(2022YFA1203600)the National Natural Science Foundation of China(U2032161,21925110,22321001,21890750)+3 种基金CAS Project for Young Scientists in Basic Research(YSBR-070)USTC Research Funds of the Double First-Class Initiative(YD2060002004)the Youth Innovation Promotion Association CAS(2018500)the Key R&D Program of Shandong Province(2021CXGC010302)。
基金supported by the National Natural Science Foundation of China(Grant No.U2032153)the National Key R&D Program of China(Grant No.2017YFA0402901)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB25000000)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302802)the Users with Excellence Program of Hefei Science Center of the Chinese Academy of Sciences(Grant No.2021HSC-UE004)the Fundamental Research Funds for the Central Universities(Grant No.WK2310000104)。
文摘Ta_(2)NiSe_(5)is a promising candidate for hosting an excitonic insulator(EI)phase,a novel electronic state driven by electron-hole Coulomb attraction.However,the role of electron-lattice coupling in the formation of the EI phase remains controversial.Here,we use angle-resolved photoemission spectroscopy(ARPES)to study the band structure evolution of Ta_(2)Ni(Se_(1-x)S_(x))_(5)with sulfur substitution and potassium deposition,which modulate the band gap and the carrier concentration,respectively.We find that the Ta 5d states originating from the bottom of the conduction band persist at the top of the valence band in the low-temperature monoclinic phase,indicating the importance of exciton condensation in opening the gap in the semi-metallic band structure.We also observe that the characteristic overlap between the conduction and valence bands can be restored in the monoclinic lattice by mild carrier injection,suggesting that the lattice distortion in the monoclinic phase is not the main factor for producing the insulating gap,but rather the exciton condensation in the electronic system is the dominant driving force.Our results shed light on the electron-lattice decoupling and the origin of the EI phase in Ta_(2)Ni(Se_(1-x)Sx)_(5).
基金This work was financially supported by the National Key R&D Program of Chnia(No.2017YFA0207301)the National Natural Science Foundation of China(Nos.U1632154,21890751,91745113,11621063,21601172,and J1030412)+2 种基金National Program for Support of Top-notch Young Professionals,the Fundamental Research Funds for the Central Universities(No.WK2090050043)Youth Innovation Promotion Association of CAS(No.2018500)Users with Excellence Project of Hefei Science Center(No.CAS2018HSCUE002).
文摘Perovskite oxides are significant candidates to develop electrochemical catalysts for water oxidation in consideration of their high catalysis capacity,low costing and excellent stability.Rational design of coordination structure and overcoming poor electronic transport are regarded as critical factors for outstanding perovskite-based oxygen evolution reaction (OER) catalysts.Herein,we report a mild chemical oxidation method to realize ligancy engineering from strongly-correlated brownmillerite Sr2Co2O5 to perovskite phase Sr2Co2O5.5,along with abundant oxygen vacancies formation and greatly boosted electric conductivity,which helps to form the active species of Co hydroxide/oxide on the surface of catalysts.The coupling effect of catalytic kinetics and unimpeded electronic movement brings high OER activities in Sr2Co2O5.5 with a low onset potential and a small Tafel slope.Our work not only displays in-depth understanding into the relationship among catalysis performance and multiple physical degrees of freedom,but also paves a new path to develop high-efficient electrochemical catalysts.
