The development of active yet stable catalysts for oxygen reduction reaction(ORR)is still a major issue for the extensive permeation of fuel cells into everyday technology.While nanostructured Pt catalysts are to date...The development of active yet stable catalysts for oxygen reduction reaction(ORR)is still a major issue for the extensive permeation of fuel cells into everyday technology.While nanostructured Pt catalysts are to date the best available systems in terms of activity,the same is not true for stability,particularly under operating conditions.In this work,Pt_(Х)Y alloy nanoparticles are proposed as active and durable electrocatalysts for ORR.Pt_(Х)Y nanoalloys are synthesized and further optimized by laser ablation in liquid followed by laser fragmentation in liquid.The novel integrated laser-assisted methodology succeeded in producing Pt_(Х)Y nanoparticles with the ideal size(<10 nm)of commercial Pt catalysts,yet resulting remarkably more active with E_(1/2)=0.943 V vs.RHE,specific activity=1095μA cm^(-2) and mass activity>1000 A g^(-1).At the same time,the nanoalloys are embedded in a fine Pt oxide matrix,which allows a greater stability of the catalyst than the commercial Pt reference,as directly verified on a gas diffusion electrode.展开更多
P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phas...P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phases remains a necessity.Herein,we design a P2/O3-type Na_(0.76)Ni_(0.31)Zn_(0.07)Mn_(0.50)Ti_(0.12)0_(2)(NNZMT)with high chemical/electrochemical stability by enhancing the coupling between the two phases.For the first time,a unique Na*extraction is observed from a Na-rich O3 phase by a Na-poor P2 phase and systematically investigated.This process is facilitated by Zn^(2+)/Ti^(4+)dual doping and calcination condition regulation,allowing a higher Na*content in the P2 phase with larger Na^(+)transport channels and enhancing Na transport kinetics.Because of reduced Na^(+)in the O3 phase,which increases the difficulty of H^(+)/Na^(+) exchange,the hydrostability of the O3 phase in NNZMT is considerably improved.Furthermore,Zn^(2+)/Ti^(4+)presence in NNZMT synergistically regulates oxygen redox chemistry,which effectively suppresses O_(2)/CO_(2) gas release and electrolyte decomposition,and completely inhibits phase transitions above 4.0 V.As a result,NNZMT achieves a high discharge capacity of 144.8 mA h g^(-1) with a median voltage of 3.42 V at 20 mA g^(-1) and exhibits excellent cycling performance with a capacity retention of 77.3% for 1000 cycles at 2000 mA g^(-1).This study provides an effective strategy and new insights into the design of high-performance layered-oxide cathode materials with enhanced structure/interface stability forSIBs.展开更多
The effect of different molar ratios of Y2O3 and Y(NO3)3 on the microstructure and electrical response of ZnO-Bi2O3-based varistor ceramics sintered at 1 000 °C was investigated, and the mechanism by which this d...The effect of different molar ratios of Y2O3 and Y(NO3)3 on the microstructure and electrical response of ZnO-Bi2O3-based varistor ceramics sintered at 1 000 °C was investigated, and the mechanism by which this doping improves the electrical characteristics of ZnO-Bi2O3-based varistor ceramics was discussed. With increasing amounts of Y(NO3)3 or Y2O3 in the starting composition, Y2O3, Sb2O4 and Y-containing Bi-rich phase form, and the average grain size significantly decreases. The average grain size significantly decreases as the contents of rare earth compounds of Y(NO3)3 or Y2O3 increase. The maximum value of the nonlinear coefficient is found at 0.16% Y(NO3)3 or 0.02% Y2O3 (molar fraction) doped varistor ceramics, and there is an increase of 122% or 35% compared with the varistor ceramics without Y(NO3)3 or Y2O3. The threshold voltage VT of Y(NO3)3 and Y2O3 reaches at 1 460 V/mm and 1 035 V/mm, respectively. The results also show that varistor sample doped with Y(NO3)3 has a remarkably more homogeneous and denser microstructure in comparison to the sample doped with Y2O3.展开更多
Physical vapor deposition(PVD)can be used to produce high-quality Gd_(2)O_(3)-doped CeO2(GDC)films.Among various PVD methods,reactive sputtering provides unique benefits,such as high deposition rates and easy upscalin...Physical vapor deposition(PVD)can be used to produce high-quality Gd_(2)O_(3)-doped CeO2(GDC)films.Among various PVD methods,reactive sputtering provides unique benefits,such as high deposition rates and easy upscaling for industrial applications.GDC thin films were successfully fabricated through reactive sputtering using a Gd_(0.2)Ce_(0.8)(at%)metallic target,and their application in solid oxide fuel cells,such as buffer layers between yttria-stabilized zirconia(YSZ)/La0.6Sr0.4Co0.2Fe0.8O_(3−δ)and as sublayers in the steel/coating system,was evaluated.First,the direct current(DC)reactive-sputtering behavior of the GdCe metallic target was determined.Then,the GDC films were deposited on NiO-YSZ/YSZ half-cells to investigate the influence of oxygen flow rate on the quality of annealed GDC films.The results demonstrated that reactive sputtering can be used to prepare thin and dense GDC buffer layers without high-temperature sintering.Furthermore,the cells with a sputtered GDC buffer layer showed better electrochemical performance than those with a screen-printed GDC buffer layer.In addition,the insertion of a GDC sublayer between the SUS441 interconnects and the Mn-Co spinel coatings contributed to the reduction of the oxidation rate for SUS441 at operating temperatures,according to the area-specific resistance tests.展开更多
The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X...The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.展开更多
Based on selective volatilization taking place among elements in graphite furnace, a new method for direct determination of trace titanium in high purity yttrium oxide by fluorination electrothermal vaporization(FETV)...Based on selective volatilization taking place among elements in graphite furnace, a new method for direct determination of trace titanium in high purity yttrium oxide by fluorination electrothermal vaporization(FETV)/ICP AES has been proposed. The vaporization behavior of the analyte and matrix element was studied in detail. Various factors of influence on vaporization of analyte were also investigated. Under optimal experimental conditions, the detection limit(3 σ ) of Ti is 1 0 ng/ml, and the RSD is 2 3%( n =10, c =0 2 μg/ml). The proposed method is simple, rapid and sensitive, and pretreatment is not necessary. This method can be used to directly determine trace refractory impurity titanium in high purity powder sample(Y 2O 3). The recovery for sample analysis is more than 96%.展开更多
基金the P-DISC Grant PROMETEO(project number:P-DiSC#03NExuS_BIRD2021-UNIPD)DYNAMO(project number:P-P-DiSC#01BIRD2020-UNIPD)the financial support of the Fellowship in Applied Electrochemistry 2020。
文摘The development of active yet stable catalysts for oxygen reduction reaction(ORR)is still a major issue for the extensive permeation of fuel cells into everyday technology.While nanostructured Pt catalysts are to date the best available systems in terms of activity,the same is not true for stability,particularly under operating conditions.In this work,Pt_(Х)Y alloy nanoparticles are proposed as active and durable electrocatalysts for ORR.Pt_(Х)Y nanoalloys are synthesized and further optimized by laser ablation in liquid followed by laser fragmentation in liquid.The novel integrated laser-assisted methodology succeeded in producing Pt_(Х)Y nanoparticles with the ideal size(<10 nm)of commercial Pt catalysts,yet resulting remarkably more active with E_(1/2)=0.943 V vs.RHE,specific activity=1095μA cm^(-2) and mass activity>1000 A g^(-1).At the same time,the nanoalloys are embedded in a fine Pt oxide matrix,which allows a greater stability of the catalyst than the commercial Pt reference,as directly verified on a gas diffusion electrode.
基金supported by the National Natural Science Foundation of China (22169002)the Chongzuo Key Research and Development Program of China (20220603)the Counterpart Aid Project for Discipline Construction from Guangxi University(2023M02)
文摘P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phases remains a necessity.Herein,we design a P2/O3-type Na_(0.76)Ni_(0.31)Zn_(0.07)Mn_(0.50)Ti_(0.12)0_(2)(NNZMT)with high chemical/electrochemical stability by enhancing the coupling between the two phases.For the first time,a unique Na*extraction is observed from a Na-rich O3 phase by a Na-poor P2 phase and systematically investigated.This process is facilitated by Zn^(2+)/Ti^(4+)dual doping and calcination condition regulation,allowing a higher Na*content in the P2 phase with larger Na^(+)transport channels and enhancing Na transport kinetics.Because of reduced Na^(+)in the O3 phase,which increases the difficulty of H^(+)/Na^(+) exchange,the hydrostability of the O3 phase in NNZMT is considerably improved.Furthermore,Zn^(2+)/Ti^(4+)presence in NNZMT synergistically regulates oxygen redox chemistry,which effectively suppresses O_(2)/CO_(2) gas release and electrolyte decomposition,and completely inhibits phase transitions above 4.0 V.As a result,NNZMT achieves a high discharge capacity of 144.8 mA h g^(-1) with a median voltage of 3.42 V at 20 mA g^(-1) and exhibits excellent cycling performance with a capacity retention of 77.3% for 1000 cycles at 2000 mA g^(-1).This study provides an effective strategy and new insights into the design of high-performance layered-oxide cathode materials with enhanced structure/interface stability forSIBs.
基金Project(BK2011243) supported by the Natural Science Foundation of Jiangsu Province, ChinaProject(EIPE11204) supported by the State Key Laboratory of Electrical Insulation and Power Equipment, China+4 种基金Project(KF201104) supported by the State Key Laboratory of New Ceramic and Fine Processing, ChinaProject(KFJJ201105) supported by the Opening Program of State key Laboratory of Electronic Thin Films and Integrated Devices, ChinaProject(2011-22) supported by the State Key Laboratory of Inorganic Synthesis and Preparative Chemistry of Jilin University, ChinaProject(10KJD430002) supported by the Universities Natural Science Research Project of Jiangsu Province, ChinaProject(11JDG084) supported by the Research Foundation of Jiangsu University, China
文摘The effect of different molar ratios of Y2O3 and Y(NO3)3 on the microstructure and electrical response of ZnO-Bi2O3-based varistor ceramics sintered at 1 000 °C was investigated, and the mechanism by which this doping improves the electrical characteristics of ZnO-Bi2O3-based varistor ceramics was discussed. With increasing amounts of Y(NO3)3 or Y2O3 in the starting composition, Y2O3, Sb2O4 and Y-containing Bi-rich phase form, and the average grain size significantly decreases. The average grain size significantly decreases as the contents of rare earth compounds of Y(NO3)3 or Y2O3 increase. The maximum value of the nonlinear coefficient is found at 0.16% Y(NO3)3 or 0.02% Y2O3 (molar fraction) doped varistor ceramics, and there is an increase of 122% or 35% compared with the varistor ceramics without Y(NO3)3 or Y2O3. The threshold voltage VT of Y(NO3)3 and Y2O3 reaches at 1 460 V/mm and 1 035 V/mm, respectively. The results also show that varistor sample doped with Y(NO3)3 has a remarkably more homogeneous and denser microstructure in comparison to the sample doped with Y2O3.
基金financially supported by the National Key R&D Program of China (No. 2018YFB1502203-1)the Guangdong Basic and Applied Basic Research Foundation (No. 2021B1515120087)the Stable Supporting Fund of Shenzhen, China (No. GXWD20201230155427003-202007 28114835006)
文摘Physical vapor deposition(PVD)can be used to produce high-quality Gd_(2)O_(3)-doped CeO2(GDC)films.Among various PVD methods,reactive sputtering provides unique benefits,such as high deposition rates and easy upscaling for industrial applications.GDC thin films were successfully fabricated through reactive sputtering using a Gd_(0.2)Ce_(0.8)(at%)metallic target,and their application in solid oxide fuel cells,such as buffer layers between yttria-stabilized zirconia(YSZ)/La0.6Sr0.4Co0.2Fe0.8O_(3−δ)and as sublayers in the steel/coating system,was evaluated.First,the direct current(DC)reactive-sputtering behavior of the GdCe metallic target was determined.Then,the GDC films were deposited on NiO-YSZ/YSZ half-cells to investigate the influence of oxygen flow rate on the quality of annealed GDC films.The results demonstrated that reactive sputtering can be used to prepare thin and dense GDC buffer layers without high-temperature sintering.Furthermore,the cells with a sputtered GDC buffer layer showed better electrochemical performance than those with a screen-printed GDC buffer layer.In addition,the insertion of a GDC sublayer between the SUS441 interconnects and the Mn-Co spinel coatings contributed to the reduction of the oxidation rate for SUS441 at operating temperatures,according to the area-specific resistance tests.
基金financially supported by (i) Suranaree University of Technology,(ii) Thailand Science Research and Innovation,and (iii) National Science,Research and Innovation Fund(project codes 90464 and 160363)。
文摘The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.
文摘Based on selective volatilization taking place among elements in graphite furnace, a new method for direct determination of trace titanium in high purity yttrium oxide by fluorination electrothermal vaporization(FETV)/ICP AES has been proposed. The vaporization behavior of the analyte and matrix element was studied in detail. Various factors of influence on vaporization of analyte were also investigated. Under optimal experimental conditions, the detection limit(3 σ ) of Ti is 1 0 ng/ml, and the RSD is 2 3%( n =10, c =0 2 μg/ml). The proposed method is simple, rapid and sensitive, and pretreatment is not necessary. This method can be used to directly determine trace refractory impurity titanium in high purity powder sample(Y 2O 3). The recovery for sample analysis is more than 96%.
