使用GGA+U方法研究了Ca O或Ba O与Sm2O3共掺杂Ce O2体系几何和电子结构及氧离子迁移。计算结果表明,Ba和Sm均靠近氧空位时Ba Sm Ce30O63体系最稳定;Sm靠近,Ca远离氧空位时Ca Sm Ce30O63体系最稳定。Ba Sm Ce30O63和Ca Sm Ce30O63体系中...使用GGA+U方法研究了Ca O或Ba O与Sm2O3共掺杂Ce O2体系几何和电子结构及氧离子迁移。计算结果表明,Ba和Sm均靠近氧空位时Ba Sm Ce30O63体系最稳定;Sm靠近,Ca远离氧空位时Ca Sm Ce30O63体系最稳定。Ba Sm Ce30O63和Ca Sm Ce30O63体系中均不存在Ce4+变价。对Ca Sm Ce30O63体系氧离子迁移的研究发现,当氧离子迁移到空位时,迁移能大小顺序为Em(3→V)<Em(1→V)<Em(4→V)<Em(2→V),这一规律源于氧离子与低价掺杂离子产生负电势之间的排斥作用;对Ba Sm Ce30O63体系氧离子迁移的研究发现,当空位迁移到周围氧离子时,迁移能大小顺序为Em(V→3)<Em(V→5)<Em(V→1),这一规律源于氧空位产生的正电势与低价掺杂离子产生的负电势之间的吸引作用。此外,Ca Sm Ce30O63体系最小迁移能小于Sm Ce31O63体系,证实了Ce O2-Sm2O3-Ca O体系离子电导率大于Ce O2-Sm2O3体系的实验结果。展开更多
Structures of stable compositions of sodium oxide cluster cations (NanOm+,n≤11) have been investigated by ion mobility mass spectrometry. Stoichiometric compositions series, Na(Na2O)(n-1)/2^+(n=3, 5, 7, 9, and 11), w...Structures of stable compositions of sodium oxide cluster cations (NanOm+,n≤11) have been investigated by ion mobility mass spectrometry. Stoichiometric compositions series, Na(Na2O)(n-1)/2^+(n=3, 5, 7, 9, and 11), were observed as stable composition series, and NaO(Na2O)(n-1)/2^+ series (n=5, 7, 9, and 11) were observed as secondary stable series in the mass spectra. To assign the structures of these cluster ion series, collision cross sections between the ions and helium buffer gas were determined experimentally from the ion mobility measurements. Theoretical collision cross sections were also calculated for optimized structures of these compositions. Finally, the structures of Na(Na2O)(n-1)/2^+ and NaO(Na2O)(n-1)/2^+ were assigned to those having similar structural frames for each n except for n=9. All bonds in the assigned structures of Na(Na2O)(n-1)/2^+ were between sodium and oxygen. On the other hand, there was one O-O bond in addition to Na-O bonds in NaO(Na2O)(n-1)/2^+. This result indicates that NaO(Na2O)(n-1)/2^+ have a peroxide ion (O22-) as a substitute for an oxide ion (O2-) of Na(Na2O)(n-1)/2^+. As a result, both stable series, Na(Na2O)(n-1)/2^+ and NaO(Na2O)(n-1)/2^+, are closed-shell compositions. These closed-shell characteristics have a strong influence on the stability of sodium oxide cluster cations.展开更多
Here, we report a study of ion transport across graphene oxide （GO） membranes of various thicknesses, made by vacuum filtration of GO aqueous solutions. The diffusive transport rates of two charge-equivalent rutheni...Here, we report a study of ion transport across graphene oxide （GO） membranes of various thicknesses, made by vacuum filtration of GO aqueous solutions. The diffusive transport rates of two charge-equivalent ruthenium complex ions Ru（bpy）3^2＋ and Ru（phen）32% with a sub-angstrom size difference, are distinguishable through GO membranes and their ratio can be a unique tool for probing the transport-relevant pore structures. Pore and slit-dominant hindered diffusion models are presented and correlated to experimental results. Our analysis suggests that ion transport is mostly facilitated by large pores （larger than 1.75 nm in diameter） in the relatively thin GO membranes, while slits formed by GO stacking （less than 1.42 nm in width） become dominant only in thick membranes. By grafting PEG molecules to the lateral plane of GO sheets, membranes with enlarged interlayer spacing were engineered, which showed drastically increased ion transport rates and lower distinction among the two ruthenium complex ions, consistent with the prediction by the slit-dominant steric hindered diffusion model.展开更多
Large-scale single crystals have potential applications in many fields,such as in ferroelectric and photoelectric energy conversion devices.Perovskite oxynitrides have also attracted attention in photoelectrochemical ...Large-scale single crystals have potential applications in many fields,such as in ferroelectric and photoelectric energy conversion devices.Perovskite oxynitrides have also attracted attention in photoelectrochemical water splitting systems because of their high theoretical solar-to-hydrogen efficiencies.Nevertheless,the synthesis of perovskite oxynitride single crystals requires the coupling of cation exchange and ammonization processes,which is exceptionally challenging.The present study demonstrates an inorganic vapor method that provides,for the first time ever,high-quality epitaxial perovskite SrTaO_(2)N single crystals on the centimeter scale.Assessments using Raman spectroscopy,crystal structure analysis and density functional theory determined that the conversion mechanism followed a topotactic transition mode.Compared with conventional SrTaO_(2)N particle-assembled films,the SrTaO_(2)N single crystals made in this work were free of interparticle interfaces and grain boundaries,which exhibited extremely high performance during photoelectrochemical water oxidation.In particular,these SrTaO_(2)N single crystals showed the highest photocurrent density at 0.6 V vs.RHE(1.20 mA cm^(−2)) and the highest photocurrent filling factor(47.6%)reported to date,together with a low onset potential(0.35 V vs.RHE).This onset potential was 200 mV less than that of the reported in situ SrTaO_(2)N film,and the photocurrent fill factor was improved by 2 to 3 times.展开更多
文摘使用GGA+U方法研究了Ca O或Ba O与Sm2O3共掺杂Ce O2体系几何和电子结构及氧离子迁移。计算结果表明,Ba和Sm均靠近氧空位时Ba Sm Ce30O63体系最稳定;Sm靠近,Ca远离氧空位时Ca Sm Ce30O63体系最稳定。Ba Sm Ce30O63和Ca Sm Ce30O63体系中均不存在Ce4+变价。对Ca Sm Ce30O63体系氧离子迁移的研究发现,当氧离子迁移到空位时,迁移能大小顺序为Em(3→V)<Em(1→V)<Em(4→V)<Em(2→V),这一规律源于氧离子与低价掺杂离子产生负电势之间的排斥作用;对Ba Sm Ce30O63体系氧离子迁移的研究发现,当空位迁移到周围氧离子时,迁移能大小顺序为Em(V→3)<Em(V→5)<Em(V→1),这一规律源于氧空位产生的正电势与低价掺杂离子产生的负电势之间的吸引作用。此外,Ca Sm Ce30O63体系最小迁移能小于Sm Ce31O63体系,证实了Ce O2-Sm2O3-Ca O体系离子电导率大于Ce O2-Sm2O3体系的实验结果。
基金supported by JSPS KAKENHI Grant (No.JP18K14173, No.JP17K14433, and No.JP17J02017)a JSPS Research Fellowship
文摘Structures of stable compositions of sodium oxide cluster cations (NanOm+,n≤11) have been investigated by ion mobility mass spectrometry. Stoichiometric compositions series, Na(Na2O)(n-1)/2^+(n=3, 5, 7, 9, and 11), were observed as stable composition series, and NaO(Na2O)(n-1)/2^+ series (n=5, 7, 9, and 11) were observed as secondary stable series in the mass spectra. To assign the structures of these cluster ion series, collision cross sections between the ions and helium buffer gas were determined experimentally from the ion mobility measurements. Theoretical collision cross sections were also calculated for optimized structures of these compositions. Finally, the structures of Na(Na2O)(n-1)/2^+ and NaO(Na2O)(n-1)/2^+ were assigned to those having similar structural frames for each n except for n=9. All bonds in the assigned structures of Na(Na2O)(n-1)/2^+ were between sodium and oxygen. On the other hand, there was one O-O bond in addition to Na-O bonds in NaO(Na2O)(n-1)/2^+. This result indicates that NaO(Na2O)(n-1)/2^+ have a peroxide ion (O22-) as a substitute for an oxide ion (O2-) of Na(Na2O)(n-1)/2^+. As a result, both stable series, Na(Na2O)(n-1)/2^+ and NaO(Na2O)(n-1)/2^+, are closed-shell compositions. These closed-shell characteristics have a strong influence on the stability of sodium oxide cluster cations.
文摘Here, we report a study of ion transport across graphene oxide （GO） membranes of various thicknesses, made by vacuum filtration of GO aqueous solutions. The diffusive transport rates of two charge-equivalent ruthenium complex ions Ru（bpy）3^2＋ and Ru（phen）32% with a sub-angstrom size difference, are distinguishable through GO membranes and their ratio can be a unique tool for probing the transport-relevant pore structures. Pore and slit-dominant hindered diffusion models are presented and correlated to experimental results. Our analysis suggests that ion transport is mostly facilitated by large pores （larger than 1.75 nm in diameter） in the relatively thin GO membranes, while slits formed by GO stacking （less than 1.42 nm in width） become dominant only in thick membranes. By grafting PEG molecules to the lateral plane of GO sheets, membranes with enlarged interlayer spacing were engineered, which showed drastically increased ion transport rates and lower distinction among the two ruthenium complex ions, consistent with the prediction by the slit-dominant steric hindered diffusion model.
基金supported by the National Key Research and Development Program of China(2018YFA0209303)the National Natural Science Foundation of China(22025202 and 51972165)Natural Science Foundation of Jiangsu Province(BK20202003)。
文摘Large-scale single crystals have potential applications in many fields,such as in ferroelectric and photoelectric energy conversion devices.Perovskite oxynitrides have also attracted attention in photoelectrochemical water splitting systems because of their high theoretical solar-to-hydrogen efficiencies.Nevertheless,the synthesis of perovskite oxynitride single crystals requires the coupling of cation exchange and ammonization processes,which is exceptionally challenging.The present study demonstrates an inorganic vapor method that provides,for the first time ever,high-quality epitaxial perovskite SrTaO_(2)N single crystals on the centimeter scale.Assessments using Raman spectroscopy,crystal structure analysis and density functional theory determined that the conversion mechanism followed a topotactic transition mode.Compared with conventional SrTaO_(2)N particle-assembled films,the SrTaO_(2)N single crystals made in this work were free of interparticle interfaces and grain boundaries,which exhibited extremely high performance during photoelectrochemical water oxidation.In particular,these SrTaO_(2)N single crystals showed the highest photocurrent density at 0.6 V vs.RHE(1.20 mA cm^(−2)) and the highest photocurrent filling factor(47.6%)reported to date,together with a low onset potential(0.35 V vs.RHE).This onset potential was 200 mV less than that of the reported in situ SrTaO_(2)N film,and the photocurrent fill factor was improved by 2 to 3 times.
