Iron‐based pyrophosphates are attractive cathodes for sodium‐ion batteries due to their large framework,cost‐effectiveness,and high energy density.However,the understanding of the crystal structure is scarce and on...Iron‐based pyrophosphates are attractive cathodes for sodium‐ion batteries due to their large framework,cost‐effectiveness,and high energy density.However,the understanding of the crystal structure is scarce and only a limited candidates have been reported so far.In this work,we found for the first time that a continuous solid solution,Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2)(0≤α≤1,could be obtained by mutual substitution of cations at center‐symmetric Na3 and Na4 sites while keeping the crystal building blocks of anionic P_(2)O_(7) unchanged.In particular,a novel off‐stoichiometric Na_(3)Fe(2.5)(P_(2)O_(7))_(2)is thus proposed,and its structure,energy storage mechanism,and electrochemical performance are extensively investigated to unveil the structure–function relationship.The as‐prepared off‐stoichiometric electrode delivers appealing performance with a reversible discharge capacity of 83 mAh g^(−1),a working voltage of 2.9 V(vs.Na^(+)/Na),the retention of 89.2%of the initial capacity after 500 cycles,and enhanced rate capability of 51 mAh g^(−1)at a current density of 1600 mA g^(−1).This research shows that sodium ferric pyrophosphate could form extended solid solution composition and promising phase is concealed in the range of Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2),offering more chances for exploration of new cathode materials for the construction of high‐performance SIBs.展开更多
Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type mi...Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type microemulison region, so it is the proper system to prepare Ce0.6Zr0.4O2 solid solution ultrafine particle. Some physical-chemical techniques such as TG/DTA, XRD, BET, and HRTEM are used to characterize the resultant powders. The results show that the fluorite cubic Ce0.6Zr0.4O2 solid solution is obtained at 400 ℃. The surface area is （146.7 m^2·g^-1）, which is higher than the surface area for sol-gel prepared sample （59.5m^2·g^-1）. HRTEM images indicated that the Ce0.6Zr0.4O2 solid solution ultrafine particle is well-crystallized, narrow size distribution, less agglomeration, within mean size of 5 -7 nm.展开更多
The CeO_2-ZrO_2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface are...The CeO_2-ZrO_2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface area and XRD analysis. The studies indicate that the separation of the microemulsion phase during the preparation procedure can decrease the specific surface area of sample, adding hydrogen peroxide in the matrix solution can increase the specific surface area and stability of sample. The surface area of sample calcined at 550 ℃ for 5 h is 149 m^2·g^(-1), and that calcined at 900 ℃ for 6 h is 88 m^2·g^(-1). The sample with tetragonal symmetry Ce_(0.5)Zr_(0.5)O_2 phase has a higher stability.展开更多
A series of SnO2‐based catalysts modified by Mn, Zr, Ti and Pb oxides with a Sn/M （M=Mn, Zr, Ti and Pb） molar ratio of 9/1 were prepared by a co‐precipitation method and used for CH4 and CO oxidation. The Mn3＋, ...A series of SnO2‐based catalysts modified by Mn, Zr, Ti and Pb oxides with a Sn/M （M=Mn, Zr, Ti and Pb） molar ratio of 9/1 were prepared by a co‐precipitation method and used for CH4 and CO oxidation. The Mn3＋, Zr4＋, Ti4＋and Pb4＋cations are incorporated into the lattice of tetragonal rutile SnO2 to form a solid solution structure. As a consequence, the surface area and thermal stability of the catalysts are improved. Moreover, the oxygen species of the modified catalysts become easier to be reduced. Therefore, the oxidation activity over the catalysts was improved, except for the one modified by Pb oxide. Manganese oxide demonstrates the best promotional effects for SnO2. Using an X‐ray diffraction extrapolation method, the lattice capacity of SnO2 for Mn2O3 was 0.135 g Mn2O3/g SnO2, which indicates that to form stable solid solution, only 21%Sn4＋cations in the lattice can be maximally replaced by Mn3＋. If the amount of Mn3＋cations is over the capacity, Mn2O3 will be formed, which is not favorable for the activity of the catalysts. The Sn rich samples with only Sn‐Mn solid solution phase show higher activity than the ones with excess Mn2O3 species.展开更多
In order to reduce the oxidizing and volatilizing caused by Mg element in the traditional methods for synthesizing Mg2Sil-xSnx （x=0.2, 0.4, 0.6, 0.8） solid solutions, microwave irradiation techniques were used in pr...In order to reduce the oxidizing and volatilizing caused by Mg element in the traditional methods for synthesizing Mg2Sil-xSnx （x=0.2, 0.4, 0.6, 0.8） solid solutions, microwave irradiation techniques were used in preparing them as thermoelectric materials. Structure and phase composition of the obtained materials were investigated by X-ray diffraction （XRD）. The electrical conductivity, Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 750 K. It is found that Mg2Si1-xSnx solid solutions are well formed with excessive content of 5% （molar fraction） Mg from the stoichiometric MgESil.xSnx under microwave irradiation. A maximum dimensionless figure of merit, ZT, of about 0.26 is obtained for Mg2Si1-xSnx solid solutions at about 500 K for x=0.6.展开更多
CexZr1-xO2 complex oxides doped by transition metal(Fe, Mn, Cu) were prepared by precipitation method. Thermal stability of samples was characterized by XRD, surface areas were measured by BET method and reductive pro...CexZr1-xO2 complex oxides doped by transition metal(Fe, Mn, Cu) were prepared by precipitation method. Thermal stability of samples was characterized by XRD, surface areas were measured by BET method and reductive property was characterized by TPR. The results show that MnO2 can be dispersed in solid solution after calcined at 1273 K, when the loading is 12%, while Fe and Cu is easy to separate from samples at this temperature. Samples doped simultaneously by Fe, Mn or Fe, Cu demonstrated high reactive property at low temperature. The starting reduction temperature are 413 and 373 K, respectively. TPR results also show a broad range of reductive temperature exists in these bi-metal doped samples.展开更多
The three way catalysts (TWCs) promoters (Ce Zr)O 2, (Pr Ce Zr)O 2 and (Pr Zr)O 2 were prepared by sol gel like method. They were characterized by XRD, EXAFS and BET surface area determination. The reduction ...The three way catalysts (TWCs) promoters (Ce Zr)O 2, (Pr Ce Zr)O 2 and (Pr Zr)O 2 were prepared by sol gel like method. They were characterized by XRD, EXAFS and BET surface area determination. The reduction features of the promoters were measured by temperature programmed reduction (TPR) of H 2 to access the potential for the promoters containing praseodymia as oxygen storage component in three way catalyst. The (Pr Zr)O 2 cubic solid solution is formed at high temperature up to 800 ℃, which makes it more reducible than the (Ce Zr)O 2 solid solution. For the (Pr Ce Zr)O 2 samples, the ternary solid solution plays an important role in the reduction process. The performance of the three way catalysts with fully formulated Pt, Pd and Rh is proceeded by using both light off temperature under a stoichiometric gas composition and the conversion of CO, C 3H 6 and NO under changing air/fuel ratio at a constant reaction temperature 400 ℃ . The results indicate that a small amount of praseodymia doping into (Ce Zr)O 2 favors the light off temperature of C 3H 6 and NO, and all the catalysts containing praseodymia obviously exhibits enhanced width of S value for NO conversion at lean region ( S ≥1.00).展开更多
A series of three‐dimensionally ordered macroporous(3DOM)SnO2‐based catalysts modified by the cations Ce4+,Mn3+,and Cu2+have been prepared by using a colloidal crystal templating method and tested for soot combustio...A series of three‐dimensionally ordered macroporous(3DOM)SnO2‐based catalysts modified by the cations Ce4+,Mn3+,and Cu2+have been prepared by using a colloidal crystal templating method and tested for soot combustion under loose contact condition.XRD and STEM mapping results confirm that all the secondary metal cations have entered the lattice matrix of tetragonal rutile SnO2 to form non‐continuous solid solutions,thus impeding crystallization and improving the surface areas and pore volumes of the modified catalysts.In comparison with regular SnO2 nanoparticles,the 3DOM SnO2 displays evidently improved activity,testifying that the formation of the 3DOM structure can anchor the soot particulates in the macro‐pores,which ensures that the contact of the soot particles with the active sites on the 3DOM skeleton is more easily formed,thus benefiting the target reaction.With the incorporation of the secondary metal cations,the activity of the catalyst can be further improved due to the formation of more abundant mobile oxygen species.In summary,these effects are believed to be the major factors responsible for the activity of the catalyst.展开更多
The Ce_xTh_(1-x)O_2 solid solutions were prepared by citrate sol-gel method,and their structure and reduction properties were studied. XRD shows that solid solution with cubicphase formed in all the solid solutions (x...The Ce_xTh_(1-x)O_2 solid solutions were prepared by citrate sol-gel method,and their structure and reduction properties were studied. XRD shows that solid solution with cubicphase formed in all the solid solutions (x = 0.2, 0.5, 0.8) Ce_xTh_(1-x)O_2. Raman spectrum showsthat Ce-Th complex oxides can promote the formation of oxygen vacancies. Two reduction peaks appearin the TPR profiles of Ce_xTh_(1-x)O_2 solid solution. The a peak is attributed to the reduction ofCe^(4+) on the surface, and the β peak is attributed to the reduction of bulk CeO_2. Theincorporation of Th atom into CeO_2 improves the reduction of CeO_2. Ce_xTh_(1-x)O_2 mixed oxidesare promising materials for oxygen vacancies produced, as well as catalysts for many reactionsinvolved oxygen, such as the catalysts for three-way reactions for reducing the releasing pollutantsor combustion of VOCs.展开更多
Pentalithium aluminate（β-LiAlO） and the corresponding iron-containing solid solution(Li(AlFe)O)were synthetized by solid-state reaction. All the samples were characterized structural and microstructurally by X-ray ...Pentalithium aluminate（β-LiAlO） and the corresponding iron-containing solid solution(Li(AlFe)O)were synthetized by solid-state reaction. All the samples were characterized structural and microstructurally by X-ray diffraction, solid-state nuclear magnetic resonance, scanning electron microscopy, Nadsorption-desorption and temperature-programmed desorption of CO. Results showed that 30 mol% of iron can be incorporated into the β-LiAlOcrystalline structure at aluminum positions. Moreover, iron addition induced morphological and superficial reactivity variations. Li(AlFe)Osamples chemisorbed CObetween 200 and 700 °C, where the superficial chemisorption presented the highest enhancement,in comparison to β-LiAlO. Additionally, Li(AlFe)Osamples sintered at higher temperatures thanβ-LiAlO. Isothermal COchemisorption experiments of β-LiAlOand Li(AlFe)Owere fitted to a first order reaction model, corroborating that iron enhances the COchemisorption, kinetically. When oxygen was added to the gas flow, COchemisorption process was mainly enhanced between 400 and 600 °C for the Li(AlFe)Osample in comparison to β-LiAlO. Hence, Li(AlFe)Osolid solution presented an enhanced COchemisorption process, in the presence and absence of oxygen, in comparison to β-LiAlO.展开更多
To understand the effect of the doping amount of Cu^2+ on the structure and reactivity of SnO2 in NOx-SCR with NH3, a series of Sn-Cu-O binary oxide catalysts with different Sn/Cu ratios have been prepared and thoroug...To understand the effect of the doping amount of Cu^2+ on the structure and reactivity of SnO2 in NOx-SCR with NH3, a series of Sn-Cu-O binary oxide catalysts with different Sn/Cu ratios have been prepared and thoroughly characterized. Using the XRD extrapolation method, the SnO2 lattice capacity for Cu^2+ cations is determined at 0.10 g Cu O per g of SnO2, equaling a Sn/Cu molar ratio of 84/16. Therefore, in a tetragonal rutile SnO2 lattice, only a maximum of 16% of the Sn4+ cations can be replaced by Cu^2+ to form a stable solid solution structure. If the Cu content is higher, Cu O will form on the catalyst surface, which has a negative effect on the reaction performance. For samples in a pure solid solution phase, the number of surface defects increase with increasing Cu content until it reaches the lattice capacity, as confirmed by Raman spectroscopy. As a result, the amounts of both active oxygen species and acidic sites on the surface, which critically determine the reaction performance, also increase and reach the maximum level for the catalyst with a Cu content close to the lattice capacity. A distinct lattice capacity threshold effect on the structure and reactivity of Sn-Cu binary oxide catalysts has been observed. A Sn-Cu catalyst with the best reaction performance can be obtained by doping the SnO2 matrix with the lattice capacity amount of Cu^2+.展开更多
By X-ray powder diffraction technique and oxygen content analysis, a solid solution Sm1+xBa2-xCu3Oy has been determined in the range 0≤x≤0.4. When x<0.25. the Sm1+xBa2-xCu3Oy presents orthorhombic symmetry, and ...By X-ray powder diffraction technique and oxygen content analysis, a solid solution Sm1+xBa2-xCu3Oy has been determined in the range 0≤x≤0.4. When x<0.25. the Sm1+xBa2-xCu3Oy presents orthorhombic symmetry, and the orthorhombic-tetragonaJ transition ocCurs at x = 0.25. With the increase of x, TC decreases and finally breaks. The correlation between ox ygen content and phase structure at different quench temperatures related to Sm Ba2Cu3Oy has been investigated as well展开更多
Nanosized Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） solid solutions（x = 0.00-0.20） were synthesized by means of hydrothermal method.Then the solid solutions were ball milled with Mg2Ni and Ni powders for 20 h to get the...Nanosized Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） solid solutions（x = 0.00-0.20） were synthesized by means of hydrothermal method.Then the solid solutions were ball milled with Mg2Ni and Ni powders for 20 h to get the Mg2Ni–Ni–5 mol% Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） composites.The structures and spectrum characteristics of the Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） solid solutions catalysts were analyzed systemically.XRD results showed that the doped samples exhibited single phase of CeO2 fluorite structure.The cell parameters and cell volumes were increased with increasing the doped content.Raman spectrum revealed that the peak position of F^2g mode shift to higher wavenumbers and the peak corresponding to oxygen vacancies were observed distinctly for the doped samples.UV-Vis technique indicated that the absorption peaks of Eu^3＋ and Nd^3＋ ions appeared; the bandgap energy was decreased linearly.The electrochemical and kinetic properties of the Mg2Ni–Ni–5 mol% Ce1-x（Nd0.5Eu0.5xO2-δ composites were measured.The maximum discharge capacity was increased from 722.3 mA h/g for x = 0.00 to 819.7 mA h/g for x = 0.16,and the cycle stability S20 increased from 25.0%（x = 0.00） to 42.2%（x = 0.20）.The kinetic measurement proved that the catalytic activity of composite surfaces and the hydrogen diffusion rate were improved for the composites with doped catalysts,especially for the composites with x = 0.16 and x = 0.20.The catalysis mechanism was analyzed from the point of microstructure and spectrum features of the Ce1-x（Nd0.5Eu0.5）xO2-δ solid solutions.展开更多
Ion mobility in solid solutions of the fluorite structure 50Pb2–30BiF3–20KF (I) and 50Pb2–30BiF3–20NaF (II) was studied by NMR method. Analysis of 19F, 23Na NMR spectra made it possible to reveal the character of ...Ion mobility in solid solutions of the fluorite structure 50Pb2–30BiF3–20KF (I) and 50Pb2–30BiF3–20NaF (II) was studied by NMR method. Analysis of 19F, 23Na NMR spectra made it possible to reveal the character of ion motions in the fluoride and sodium sublattices with temperature variation, to determine the types and temperature ranges in which they took place. It was found that the dominant form of ionic mobility in the samples I and II above 380 K was the diffusion of fluoride and sodium ions. According to preliminary results of electro-physical studies, the conductivity reached values of ~ 2×10–2 – 10–3 S/cm above 500 K. The solid solutions I and II can be recommended as a basis for use in the development of new functional materials.展开更多
基金National Natural Science Foundation of China,Grant/Award Numbers:21972108,U20A20249,U22A20438Changzhou Science and Technology Bureau,Grant/Award Number:CM20223017Innovation and Technology Commission(ITC)of Hong Kong,The Innovation&Technology Fund(ITF)with Project No.ITS/126/21。
文摘Iron‐based pyrophosphates are attractive cathodes for sodium‐ion batteries due to their large framework,cost‐effectiveness,and high energy density.However,the understanding of the crystal structure is scarce and only a limited candidates have been reported so far.In this work,we found for the first time that a continuous solid solution,Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2)(0≤α≤1,could be obtained by mutual substitution of cations at center‐symmetric Na3 and Na4 sites while keeping the crystal building blocks of anionic P_(2)O_(7) unchanged.In particular,a novel off‐stoichiometric Na_(3)Fe(2.5)(P_(2)O_(7))_(2)is thus proposed,and its structure,energy storage mechanism,and electrochemical performance are extensively investigated to unveil the structure–function relationship.The as‐prepared off‐stoichiometric electrode delivers appealing performance with a reversible discharge capacity of 83 mAh g^(−1),a working voltage of 2.9 V(vs.Na^(+)/Na),the retention of 89.2%of the initial capacity after 500 cycles,and enhanced rate capability of 51 mAh g^(−1)at a current density of 1600 mA g^(−1).This research shows that sodium ferric pyrophosphate could form extended solid solution composition and promising phase is concealed in the range of Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2),offering more chances for exploration of new cathode materials for the construction of high‐performance SIBs.
文摘Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type microemulison region, so it is the proper system to prepare Ce0.6Zr0.4O2 solid solution ultrafine particle. Some physical-chemical techniques such as TG/DTA, XRD, BET, and HRTEM are used to characterize the resultant powders. The results show that the fluorite cubic Ce0.6Zr0.4O2 solid solution is obtained at 400 ℃. The surface area is （146.7 m^2·g^-1）, which is higher than the surface area for sol-gel prepared sample （59.5m^2·g^-1）. HRTEM images indicated that the Ce0.6Zr0.4O2 solid solution ultrafine particle is well-crystallized, narrow size distribution, less agglomeration, within mean size of 5 -7 nm.
文摘The CeO_2-ZrO_2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface area and XRD analysis. The studies indicate that the separation of the microemulsion phase during the preparation procedure can decrease the specific surface area of sample, adding hydrogen peroxide in the matrix solution can increase the specific surface area and stability of sample. The surface area of sample calcined at 550 ℃ for 5 h is 149 m^2·g^(-1), and that calcined at 900 ℃ for 6 h is 88 m^2·g^(-1). The sample with tetragonal symmetry Ce_(0.5)Zr_(0.5)O_2 phase has a higher stability.
基金supported by the National Natural Science Foundation of China (21263015,21567016 and 21503106)the Education Department Foundation of Jiangxi Province (KJLD14005 and GJJ150016)the Natural Science Foundation of Jiangxi Province (20142BAB213013 and 20151BBE50006),which are greatly acknowledged by the authors~~
文摘A series of SnO2‐based catalysts modified by Mn, Zr, Ti and Pb oxides with a Sn/M （M=Mn, Zr, Ti and Pb） molar ratio of 9/1 were prepared by a co‐precipitation method and used for CH4 and CO oxidation. The Mn3＋, Zr4＋, Ti4＋and Pb4＋cations are incorporated into the lattice of tetragonal rutile SnO2 to form a solid solution structure. As a consequence, the surface area and thermal stability of the catalysts are improved. Moreover, the oxygen species of the modified catalysts become easier to be reduced. Therefore, the oxidation activity over the catalysts was improved, except for the one modified by Pb oxide. Manganese oxide demonstrates the best promotional effects for SnO2. Using an X‐ray diffraction extrapolation method, the lattice capacity of SnO2 for Mn2O3 was 0.135 g Mn2O3/g SnO2, which indicates that to form stable solid solution, only 21%Sn4＋cations in the lattice can be maximally replaced by Mn3＋. If the amount of Mn3＋cations is over the capacity, Mn2O3 will be formed, which is not favorable for the activity of the catalysts. The Sn rich samples with only Sn‐Mn solid solution phase show higher activity than the ones with excess Mn2O3 species.
基金Project(2009BB4228) supported by the Natural Science Foundation of Chongqing City,ChinaProject(CK2010Z09) supported by the Research Foundation of Chongqing University of Science and Technology,China
文摘In order to reduce the oxidizing and volatilizing caused by Mg element in the traditional methods for synthesizing Mg2Sil-xSnx （x=0.2, 0.4, 0.6, 0.8） solid solutions, microwave irradiation techniques were used in preparing them as thermoelectric materials. Structure and phase composition of the obtained materials were investigated by X-ray diffraction （XRD）. The electrical conductivity, Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 750 K. It is found that Mg2Si1-xSnx solid solutions are well formed with excessive content of 5% （molar fraction） Mg from the stoichiometric MgESil.xSnx under microwave irradiation. A maximum dimensionless figure of merit, ZT, of about 0.26 is obtained for Mg2Si1-xSnx solid solutions at about 500 K for x=0.6.
文摘CexZr1-xO2 complex oxides doped by transition metal(Fe, Mn, Cu) were prepared by precipitation method. Thermal stability of samples was characterized by XRD, surface areas were measured by BET method and reductive property was characterized by TPR. The results show that MnO2 can be dispersed in solid solution after calcined at 1273 K, when the loading is 12%, while Fe and Cu is easy to separate from samples at this temperature. Samples doped simultaneously by Fe, Mn or Fe, Cu demonstrated high reactive property at low temperature. The starting reduction temperature are 413 and 373 K, respectively. TPR results also show a broad range of reductive temperature exists in these bi-metal doped samples.
文摘The three way catalysts (TWCs) promoters (Ce Zr)O 2, (Pr Ce Zr)O 2 and (Pr Zr)O 2 were prepared by sol gel like method. They were characterized by XRD, EXAFS and BET surface area determination. The reduction features of the promoters were measured by temperature programmed reduction (TPR) of H 2 to access the potential for the promoters containing praseodymia as oxygen storage component in three way catalyst. The (Pr Zr)O 2 cubic solid solution is formed at high temperature up to 800 ℃, which makes it more reducible than the (Ce Zr)O 2 solid solution. For the (Pr Ce Zr)O 2 samples, the ternary solid solution plays an important role in the reduction process. The performance of the three way catalysts with fully formulated Pt, Pd and Rh is proceeded by using both light off temperature under a stoichiometric gas composition and the conversion of CO, C 3H 6 and NO under changing air/fuel ratio at a constant reaction temperature 400 ℃ . The results indicate that a small amount of praseodymia doping into (Ce Zr)O 2 favors the light off temperature of C 3H 6 and NO, and all the catalysts containing praseodymia obviously exhibits enhanced width of S value for NO conversion at lean region ( S ≥1.00).
基金the Natural Science Foundation of China(21567016,21503106)the Natural Science Foundation of Jiangxi Province(20171BAB213013)+3 种基金the Education Department Foundation of Jiangxi Province(KJLD14005)National Key Research and Development Program of China(2016YFC0209302)the Innovation Fund Designated for Graduate Students of Jiangxi Province(YC2015-B017)the Innovation Fund Designated for Undergraduate Students of China(201701035)~~
文摘A series of three‐dimensionally ordered macroporous(3DOM)SnO2‐based catalysts modified by the cations Ce4+,Mn3+,and Cu2+have been prepared by using a colloidal crystal templating method and tested for soot combustion under loose contact condition.XRD and STEM mapping results confirm that all the secondary metal cations have entered the lattice matrix of tetragonal rutile SnO2 to form non‐continuous solid solutions,thus impeding crystallization and improving the surface areas and pore volumes of the modified catalysts.In comparison with regular SnO2 nanoparticles,the 3DOM SnO2 displays evidently improved activity,testifying that the formation of the 3DOM structure can anchor the soot particulates in the macro‐pores,which ensures that the contact of the soot particles with the active sites on the 3DOM skeleton is more easily formed,thus benefiting the target reaction.With the incorporation of the secondary metal cations,the activity of the catalyst can be further improved due to the formation of more abundant mobile oxygen species.In summary,these effects are believed to be the major factors responsible for the activity of the catalyst.
文摘The Ce_xTh_(1-x)O_2 solid solutions were prepared by citrate sol-gel method,and their structure and reduction properties were studied. XRD shows that solid solution with cubicphase formed in all the solid solutions (x = 0.2, 0.5, 0.8) Ce_xTh_(1-x)O_2. Raman spectrum showsthat Ce-Th complex oxides can promote the formation of oxygen vacancies. Two reduction peaks appearin the TPR profiles of Ce_xTh_(1-x)O_2 solid solution. The a peak is attributed to the reduction ofCe^(4+) on the surface, and the β peak is attributed to the reduction of bulk CeO_2. Theincorporation of Th atom into CeO_2 improves the reduction of CeO_2. Ce_xTh_(1-x)O_2 mixed oxidesare promising materials for oxygen vacancies produced, as well as catalysts for many reactionsinvolved oxygen, such as the catalysts for three-way reactions for reducing the releasing pollutantsor combustion of VOCs.
基金financially supported by the Project SENERCONACYT(251801)CONACYT for financial support through the CONACYT-SNI research assistant system and PNPC-CONACYT,respectively
文摘Pentalithium aluminate（β-LiAlO） and the corresponding iron-containing solid solution(Li(AlFe)O)were synthetized by solid-state reaction. All the samples were characterized structural and microstructurally by X-ray diffraction, solid-state nuclear magnetic resonance, scanning electron microscopy, Nadsorption-desorption and temperature-programmed desorption of CO. Results showed that 30 mol% of iron can be incorporated into the β-LiAlOcrystalline structure at aluminum positions. Moreover, iron addition induced morphological and superficial reactivity variations. Li(AlFe)Osamples chemisorbed CObetween 200 and 700 °C, where the superficial chemisorption presented the highest enhancement,in comparison to β-LiAlO. Additionally, Li(AlFe)Osamples sintered at higher temperatures thanβ-LiAlO. Isothermal COchemisorption experiments of β-LiAlOand Li(AlFe)Owere fitted to a first order reaction model, corroborating that iron enhances the COchemisorption, kinetically. When oxygen was added to the gas flow, COchemisorption process was mainly enhanced between 400 and 600 °C for the Li(AlFe)Osample in comparison to β-LiAlO. Hence, Li(AlFe)Osolid solution presented an enhanced COchemisorption process, in the presence and absence of oxygen, in comparison to β-LiAlO.
文摘To understand the effect of the doping amount of Cu^2+ on the structure and reactivity of SnO2 in NOx-SCR with NH3, a series of Sn-Cu-O binary oxide catalysts with different Sn/Cu ratios have been prepared and thoroughly characterized. Using the XRD extrapolation method, the SnO2 lattice capacity for Cu^2+ cations is determined at 0.10 g Cu O per g of SnO2, equaling a Sn/Cu molar ratio of 84/16. Therefore, in a tetragonal rutile SnO2 lattice, only a maximum of 16% of the Sn4+ cations can be replaced by Cu^2+ to form a stable solid solution structure. If the Cu content is higher, Cu O will form on the catalyst surface, which has a negative effect on the reaction performance. For samples in a pure solid solution phase, the number of surface defects increase with increasing Cu content until it reaches the lattice capacity, as confirmed by Raman spectroscopy. As a result, the amounts of both active oxygen species and acidic sites on the surface, which critically determine the reaction performance, also increase and reach the maximum level for the catalyst with a Cu content close to the lattice capacity. A distinct lattice capacity threshold effect on the structure and reactivity of Sn-Cu binary oxide catalysts has been observed. A Sn-Cu catalyst with the best reaction performance can be obtained by doping the SnO2 matrix with the lattice capacity amount of Cu^2+.
文摘By X-ray powder diffraction technique and oxygen content analysis, a solid solution Sm1+xBa2-xCu3Oy has been determined in the range 0≤x≤0.4. When x<0.25. the Sm1+xBa2-xCu3Oy presents orthorhombic symmetry, and the orthorhombic-tetragonaJ transition ocCurs at x = 0.25. With the increase of x, TC decreases and finally breaks. The correlation between ox ygen content and phase structure at different quench temperatures related to Sm Ba2Cu3Oy has been investigated as well
基金supported by the National Natural Science Foundations of China(51501095,51371094)the Natural Science Foundation of Inner Mongolia(2017MS(LH)0516)
文摘Nanosized Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） solid solutions（x = 0.00-0.20） were synthesized by means of hydrothermal method.Then the solid solutions were ball milled with Mg2Ni and Ni powders for 20 h to get the Mg2Ni–Ni–5 mol% Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） composites.The structures and spectrum characteristics of the Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） solid solutions catalysts were analyzed systemically.XRD results showed that the doped samples exhibited single phase of CeO2 fluorite structure.The cell parameters and cell volumes were increased with increasing the doped content.Raman spectrum revealed that the peak position of F^2g mode shift to higher wavenumbers and the peak corresponding to oxygen vacancies were observed distinctly for the doped samples.UV-Vis technique indicated that the absorption peaks of Eu^3＋ and Nd^3＋ ions appeared; the bandgap energy was decreased linearly.The electrochemical and kinetic properties of the Mg2Ni–Ni–5 mol% Ce1-x（Nd0.5Eu0.5xO2-δ composites were measured.The maximum discharge capacity was increased from 722.3 mA h/g for x = 0.00 to 819.7 mA h/g for x = 0.16,and the cycle stability S20 increased from 25.0%（x = 0.00） to 42.2%（x = 0.20）.The kinetic measurement proved that the catalytic activity of composite surfaces and the hydrogen diffusion rate were improved for the composites with doped catalysts,especially for the composites with x = 0.16 and x = 0.20.The catalysis mechanism was analyzed from the point of microstructure and spectrum features of the Ce1-x（Nd0.5Eu0.5）xO2-δ solid solutions.
文摘Ion mobility in solid solutions of the fluorite structure 50Pb2–30BiF3–20KF (I) and 50Pb2–30BiF3–20NaF (II) was studied by NMR method. Analysis of 19F, 23Na NMR spectra made it possible to reveal the character of ion motions in the fluoride and sodium sublattices with temperature variation, to determine the types and temperature ranges in which they took place. It was found that the dominant form of ionic mobility in the samples I and II above 380 K was the diffusion of fluoride and sodium ions. According to preliminary results of electro-physical studies, the conductivity reached values of ~ 2×10–2 – 10–3 S/cm above 500 K. The solid solutions I and II can be recommended as a basis for use in the development of new functional materials.
