Electron density plays an important role in determining the properties of functional materials.Revealing the electron density distribution experimentally in real space can help to tune the properties of materials.Spin...Electron density plays an important role in determining the properties of functional materials.Revealing the electron density distribution experimentally in real space can help to tune the properties of materials.Spinel Li Mn2 O4 is one of the most promising cathode candidates because of its high voltage,low cost,and non-toxicity,but suffers severe capacity fading during electrochemical cycling due to the Mn dissolution.Real-space measurement of electron distribution of Li Mn2 O4 experimentally can provide direct evaluation on the strength of Mn–O bond and give an explanation of the structure stability.Here,through high energy synchrotron powder x-ray diffraction(SPXRD),accurate electron density distribution in spinel Li Mn2 O4 has been investigated based on the multipole model.The electron accumulation between Mn and O atoms in deformation density map indicates the shared interaction of Mn–O bond.The quantitative topological analysis at bond critical points shows that the Mn–O bond is relatively weak covalent interaction due to the oxygen loss.These findings suggest that oxygen stoichiometry is the key factor for preventing the Mn dissolution and capacity fading.展开更多
Oxygen vacancies play a crucial role in determining the catalytic properties of Ce-based catalysts,especially in oxidation reactions.The design of catalytic activity requires keen insight into oxygen vacancy formation...Oxygen vacancies play a crucial role in determining the catalytic properties of Ce-based catalysts,especially in oxidation reactions.The design of catalytic activity requires keen insight into oxygen vacancy formation mechanisms.In this work,we investigate the origin of oxygen vacancies in CeO_(2)from the perspective of electron density via high-energy synchrotron powder x-ray diffraction.Multipole refinement results indicate that there is no obvious hybridization between bonded Ce and O atoms in CeO_(2).Subsequent quantitative topological analysis of the experimental total electron density reveals the closed-shell interaction behavior of the Ce-O bond.The results of first-principles calculation indicate that the oxygen vacancy formation energy of CeO_(2)is the lowest among three commonly used redox catalysts.These findings indicate the relatively weak bond strength of the Ce-O bond,which induces a low oxygen vacancy formation energy for CeO_(2)and thus promotes CeO_(2)as a superior catalyst for oxidation reactions.This work provides a new direction for design of functional metal oxides with high oxygen vacancy concentrations.展开更多
基金Beijing Natural Science Foundation,China(Grant No.Z190010)the National Key Research and Development Program of China(Grant No.2019YFA0308500)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB07030200)Key Research Projects of Frontier Science of Chinese Academy of Sciences(Grant No.QYZDB-SSW-JSC035)the National Natural Science Foundation of China(Grant Nos.51421002,51672307,51991344,52025025,and 52072400).
文摘Electron density plays an important role in determining the properties of functional materials.Revealing the electron density distribution experimentally in real space can help to tune the properties of materials.Spinel Li Mn2 O4 is one of the most promising cathode candidates because of its high voltage,low cost,and non-toxicity,but suffers severe capacity fading during electrochemical cycling due to the Mn dissolution.Real-space measurement of electron distribution of Li Mn2 O4 experimentally can provide direct evaluation on the strength of Mn–O bond and give an explanation of the structure stability.Here,through high energy synchrotron powder x-ray diffraction(SPXRD),accurate electron density distribution in spinel Li Mn2 O4 has been investigated based on the multipole model.The electron accumulation between Mn and O atoms in deformation density map indicates the shared interaction of Mn–O bond.The quantitative topological analysis at bond critical points shows that the Mn–O bond is relatively weak covalent interaction due to the oxygen loss.These findings suggest that oxygen stoichiometry is the key factor for preventing the Mn dissolution and capacity fading.
基金supported by the Beijing Natural Science Foundation(Grant No.Z190010)the National Key R&D Program of China(Grant No.2019YFA0308500)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB07030200)the Key Research Projects of Frontier Science of Chinese Academy of Sciences(Grant No.QYZDB-SSW-JSC035)the National Natural Science Foundation of China(Grant Nos.51421002,51672307,51991344,and 52025025)。
文摘Oxygen vacancies play a crucial role in determining the catalytic properties of Ce-based catalysts,especially in oxidation reactions.The design of catalytic activity requires keen insight into oxygen vacancy formation mechanisms.In this work,we investigate the origin of oxygen vacancies in CeO_(2)from the perspective of electron density via high-energy synchrotron powder x-ray diffraction.Multipole refinement results indicate that there is no obvious hybridization between bonded Ce and O atoms in CeO_(2).Subsequent quantitative topological analysis of the experimental total electron density reveals the closed-shell interaction behavior of the Ce-O bond.The results of first-principles calculation indicate that the oxygen vacancy formation energy of CeO_(2)is the lowest among three commonly used redox catalysts.These findings indicate the relatively weak bond strength of the Ce-O bond,which induces a low oxygen vacancy formation energy for CeO_(2)and thus promotes CeO_(2)as a superior catalyst for oxidation reactions.This work provides a new direction for design of functional metal oxides with high oxygen vacancy concentrations.
基金supported by Beijing Natural Science Foundation(Z190010)the National Key Basic Research Program of China(2017YFA0303604,2019YFA0308500)+4 种基金the Key research projects of Frontier Science of Chinese Academy of Sciences(QYZDB-SSW-JSC035)the Youth Innovation Promotion Association of CAS(2018008)the National Natural Science Foundation of China(51672307,51991344,52025025,52072400,12074416,12074434,52250402)China National Postdoctoral Program for Innovative Talents(BX20220166)China Postdoctoral Science Foundation(2023M731863)。