Magnesium hydride serves as a promising solid-state hydrogen storage material owing to its high potential.However,its practical applications are constrained by the high enthalpy of hydrogen absorption and slow kinetic...Magnesium hydride serves as a promising solid-state hydrogen storage material owing to its high potential.However,its practical applications are constrained by the high enthalpy of hydrogen absorption and slow kinetics.In this study,we prepared a Ni/Ti3O5@graphene oxide(GO)dual-heterojunction composite material via solvent heating,electrostatic adsorption,and calcination to improve the hydrogen storage capabilities of MgH2.Adding Ni/Ti3O5@GO to MgH2 lowered the initial dehydrogenation temperature of MgH2 to 183℃;at a dehydrogenation temperature of 275℃,6.4 wt.%of H2 escaped from the MgH2 bulk.In addition,the hydrogen storage material absorbed 1.8 wt.%H2 at 30℃ for 30 min.The calculated activation energy of dehydrogenation was 48.221±0.141 kJ·mol-1,which was significantly lower than that of the ball-milled MgH2(112.63±1.44 kJ·mol-1).Mechanistic analysis results revealed that the heterojunction constructed from the multiphase compound system provided a large number of active sites and hydrogen diffusion routes,resulting in a synergistic catalytic effect that enhanced the hydrogen storage capacity of MgH2.In this work,we clarified the compositions of fuzzy interfaces in heterostructured materials by conducting ultraviolet photoelectron spectroscopy tests and identified key composite materials for the formation of heterojunctions.展开更多
Change in valency of Nb-oxide in MnO-SiO_2-Nb_2O_5 system was studied with the electrochemical method using ZrO_2 as the solid electrolyte.Thermodynamic analysis has shown that the only possible reaction that could ta...Change in valency of Nb-oxide in MnO-SiO_2-Nb_2O_5 system was studied with the electrochemical method using ZrO_2 as the solid electrolyte.Thermodynamic analysis has shown that the only possible reaction that could take place at the working elec- trode is:2(Nb_2O_5)=2(Nb_2O_4)+O_2 with the a_0 values experimentally evaluated,values of a Nb_2O:/a Nb_2O:were calculated and isoactivity-ratio curves drawn in MnO-SiO_2-Nb_2O_5 triangles at 1418 and 1585K.The simultaneous existence of tetra-and penta-valent Nb mineral constituents in industrial Nb-bearing slags was thus verified experimentally.展开更多
构建准确可靠的热力学数据库对提钒过程优化以及钒酸盐材料的制备具有重要的应用价值和指导意义。采用封闭铂金坩埚,结合X射线衍射(XRD)与差热分析(DTA)技术,证实了K2O-V2O5体系中K3V5O14为稳定存在的化合物,并试验...构建准确可靠的热力学数据库对提钒过程优化以及钒酸盐材料的制备具有重要的应用价值和指导意义。采用封闭铂金坩埚,结合X射线衍射(XRD)与差热分析(DTA)技术,证实了K2O-V2O5体系中K3V5O14为稳定存在的化合物,并试验测定了K2V8O21和KVO3的熔化温度分别为532.4℃和516.5℃。随后采用修正的准化学模型(MQM),引入溶液中第二相邻阳离子短程有序对描述吉布斯自由能的变化。基于CALPHAD框架(CALculation of PHAse Diagram,相图计算),构建了Na2O-K2O-V2O5体系的热力学模型,重现了Na2O-K2O-V2O5体系全组分范围的实验数据和热力学性质,获得了该体系中所有物相一系列自洽的热力学模型参数,最终构建了可靠的热力学数据库。进一步探讨了当前数据库在钒渣钠化焙烧提钒中的应用,明确了含钒物相的迁移规律,确定了最佳的操作温度窗口。展开更多
Zn-based thermal charging devices,utilizing the synergistic effect of ion thermoextraction and thermodiffusion,are able to efficiently convert thermal energy into electrical energy and storage in the devices,making th...Zn-based thermal charging devices,utilizing the synergistic effect of ion thermoextraction and thermodiffusion,are able to efficiently convert thermal energy into electrical energy and storage in the devices,making them a highly promising technology for low-grade heat recovery and utilization.However,the low output power density and energy conversion efficiency resulted by the slow diffusion kinetics of Zn2+hinder their development.Herein,we present a highperformance thermal charging cell design using Zn2+/NH4+hybrid ion electrolyte,which not only maintains the high output voltage of the Zn-based thermoelectric system,but also significantly enhances the output power density due to the fast diffusion kinetics of NH4+.Based on this strategy,the thermal charging cell displays a high thermopower of 12.5 mV K-1and an excellent normalized power density of 19.6 mW m-2K-2at a temperature difference of 35 K.The Carnot-relative efficiency is as high as 12.74%.Moreover,it can operate continuously for over 72 h when the temperature difference persists,achieving a balance between thermoelectric conversion and output.This work provides a simple and effective strategy for the design of high-performance thermal charging cells for low-grade heat conversion and utilization.展开更多
Hexagonal porous Nb2O5 was synthesized for the first time via a facile solid-state reaction.The structure and electrochemical properties have been optimized through tuning heating temperature.X-ray diffraction results...Hexagonal porous Nb2O5 was synthesized for the first time via a facile solid-state reaction.The structure and electrochemical properties have been optimized through tuning heating temperature.X-ray diffraction results indicate that pseudo hexagonal Nb2O5(TT-Nb2O5)and orthorhombic Nb2O5 have been synthesized at different temperatures.Hexagonal sheet and porous structure of Nb2O5 were characterized by scanning electron microscopy and N2-adsorption-desorption isotherms.The as-prepared TT-Nb2O5(heated at 600℃)shows the best performance with a remarkable charge capacity of 178 mA∙h/g at 0.2C,which is higher than that of T-Nb2O5.Even at 20℃,TT-Nb2O5 offers unprecedented rate capability up to 86 mA∙h/g.The high rate capacity is due to pseudocapacitive Li+intercalation mechanism of TT-Nb2O5.The reported results demonstrate that Nb2O5 with good crystal structure and high specific surface area is a powerful composite design for high-rate and safe anode materials.展开更多
基金supported by the National Natural Science Foundation of China[grant number U24A2044]Science and Technology Major Program of Guangxi Province[grant number GUIKEAA24206007].
摘要Magnesium hydride serves as a promising solid-state hydrogen storage material owing to its high potential.However,its practical applications are constrained by the high enthalpy of hydrogen absorption and slow kinetics.In this study,we prepared a Ni/Ti3O5@graphene oxide(GO)dual-heterojunction composite material via solvent heating,electrostatic adsorption,and calcination to improve the hydrogen storage capabilities of MgH2.Adding Ni/Ti3O5@GO to MgH2 lowered the initial dehydrogenation temperature of MgH2 to 183℃;at a dehydrogenation temperature of 275℃,6.4 wt.%of H2 escaped from the MgH2 bulk.In addition,the hydrogen storage material absorbed 1.8 wt.%H2 at 30℃ for 30 min.The calculated activation energy of dehydrogenation was 48.221±0.141 kJ·mol-1,which was significantly lower than that of the ball-milled MgH2(112.63±1.44 kJ·mol-1).Mechanistic analysis results revealed that the heterojunction constructed from the multiphase compound system provided a large number of active sites and hydrogen diffusion routes,resulting in a synergistic catalytic effect that enhanced the hydrogen storage capacity of MgH2.In this work,we clarified the compositions of fuzzy interfaces in heterostructured materials by conducting ultraviolet photoelectron spectroscopy tests and identified key composite materials for the formation of heterojunctions.
摘要Change in valency of Nb-oxide in MnO-SiO_2-Nb_2O_5 system was studied with the electrochemical method using ZrO_2 as the solid electrolyte.Thermodynamic analysis has shown that the only possible reaction that could take place at the working elec- trode is:2(Nb_2O_5)=2(Nb_2O_4)+O_2 with the a_0 values experimentally evaluated,values of a Nb_2O:/a Nb_2O:were calculated and isoactivity-ratio curves drawn in MnO-SiO_2-Nb_2O_5 triangles at 1418 and 1585K.The simultaneous existence of tetra-and penta-valent Nb mineral constituents in industrial Nb-bearing slags was thus verified experimentally.
摘要构建准确可靠的热力学数据库对提钒过程优化以及钒酸盐材料的制备具有重要的应用价值和指导意义。采用封闭铂金坩埚,结合X射线衍射(XRD)与差热分析(DTA)技术,证实了K2O-V2O5体系中K3V5O14为稳定存在的化合物,并试验测定了K2V8O21和KVO3的熔化温度分别为532.4℃和516.5℃。随后采用修正的准化学模型(MQM),引入溶液中第二相邻阳离子短程有序对描述吉布斯自由能的变化。基于CALPHAD框架(CALculation of PHAse Diagram,相图计算),构建了Na2O-K2O-V2O5体系的热力学模型,重现了Na2O-K2O-V2O5体系全组分范围的实验数据和热力学性质,获得了该体系中所有物相一系列自洽的热力学模型参数,最终构建了可靠的热力学数据库。进一步探讨了当前数据库在钒渣钠化焙烧提钒中的应用,明确了含钒物相的迁移规律,确定了最佳的操作温度窗口。
基金supported by the Leading Edge Technology of Jiangsu Province(BK20222009-X.Z.,BK20202008-X.Z.)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)National Undergraduate Innovation Training Program of NUAA(202410287179Y).
摘要Zn-based thermal charging devices,utilizing the synergistic effect of ion thermoextraction and thermodiffusion,are able to efficiently convert thermal energy into electrical energy and storage in the devices,making them a highly promising technology for low-grade heat recovery and utilization.However,the low output power density and energy conversion efficiency resulted by the slow diffusion kinetics of Zn2+hinder their development.Herein,we present a highperformance thermal charging cell design using Zn2+/NH4+hybrid ion electrolyte,which not only maintains the high output voltage of the Zn-based thermoelectric system,but also significantly enhances the output power density due to the fast diffusion kinetics of NH4+.Based on this strategy,the thermal charging cell displays a high thermopower of 12.5 mV K-1and an excellent normalized power density of 19.6 mW m-2K-2at a temperature difference of 35 K.The Carnot-relative efficiency is as high as 12.74%.Moreover,it can operate continuously for over 72 h when the temperature difference persists,achieving a balance between thermoelectric conversion and output.This work provides a simple and effective strategy for the design of high-performance thermal charging cells for low-grade heat conversion and utilization.
基金Projects(51974137,51774150)supported by the National Natural Science Foundation of ChinaProject(2020M671361)supported by China Postdoctoral Science Foundation。
摘要Hexagonal porous Nb2O5 was synthesized for the first time via a facile solid-state reaction.The structure and electrochemical properties have been optimized through tuning heating temperature.X-ray diffraction results indicate that pseudo hexagonal Nb2O5(TT-Nb2O5)and orthorhombic Nb2O5 have been synthesized at different temperatures.Hexagonal sheet and porous structure of Nb2O5 were characterized by scanning electron microscopy and N2-adsorption-desorption isotherms.The as-prepared TT-Nb2O5(heated at 600℃)shows the best performance with a remarkable charge capacity of 178 mA∙h/g at 0.2C,which is higher than that of T-Nb2O5.Even at 20℃,TT-Nb2O5 offers unprecedented rate capability up to 86 mA∙h/g.The high rate capacity is due to pseudocapacitive Li+intercalation mechanism of TT-Nb2O5.The reported results demonstrate that Nb2O5 with good crystal structure and high specific surface area is a powerful composite design for high-rate and safe anode materials.