采用共沉淀法在不同母盐溶液浓度条件下合成出Gd_2Ti_2O_7:Ce纳米粒子;用XRD、SEM、TG-DTA等测试手段分析了样品的物相、形貌及发光性能;用热分析动力学计算不同升温速率下样品的活化能。结果表明:前驱体在升温过程的物相变化分3个阶段,...采用共沉淀法在不同母盐溶液浓度条件下合成出Gd_2Ti_2O_7:Ce纳米粒子;用XRD、SEM、TG-DTA等测试手段分析了样品的物相、形貌及发光性能;用热分析动力学计算不同升温速率下样品的活化能。结果表明:前驱体在升温过程的物相变化分3个阶段,用Doyle-Ozawa和Kissinger法分别对初始浓度为0.08和0.04 mol/L条件下各阶段表观活化能进行计算,其平均值为42.43、145.58、381.98 k J·mol^(-1)和51.28、161.51、446.30 k J·mol^(-1),晶粒生长活化能分别为12.58和19.54 k J·mol^(-1)。浓度为0.08 mol/L时,1173 K煅烧2 h制备出的纳米粒子表面活性较高,铈离子掺杂0.7%(摩尔分数)时发光强度最大。展开更多
Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TB...Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TBCs was designed based on the coefficient of thermal expansion and the coating functionality,and it was completed using atmospheric plasma spraying technique.The microstructure,mechanical properties,and thermal properties were analyzed.Results indicate that the adhesion of the prepared dual-layer composite TBCs is excellent,and no noticeable cracks appear at the interface.Compared with the MoSi_(2)coating with a low fracture toughness(0.88 MPa·m^(1/2)),the Gd_(2)Zr_(2)O_(7)coating exhibits higher fracture toughness(1.74 MPa·m^(1/2))and stronger resistance to crack propagation.The prepared MoSi_(2)-Gd_(2)Zr_(2)O_(7)composite coatings have a high porosity(39%),low thermal conductivity(1.020 W·(m·K)^(−1),1200℃),and low thermal diffusivity(0.249 mm^(2)/s,1200℃).Additionally,they possess a high oxygen-vacancy concentration,which ensures excellent insulation performance.展开更多
Photocatalysis uses solar energy to convert nitrogen and water directly into ammonia,helping reduce dependence on fossil fuels and offering a way to integrate the nitrogen cycle into a clean energy network.Ohmic junct...Photocatalysis uses solar energy to convert nitrogen and water directly into ammonia,helping reduce dependence on fossil fuels and offering a way to integrate the nitrogen cycle into a clean energy network.Ohmic junctions between metals and semiconductors have demonstrated significant advantages in enhancing stability and reducing carrier recombination,but their application in photocatalytic nitrogen fixation is limited due to the difficulty of work function matching and the complexity of fabrication processes.In this study,density functional theory(DFT) calculations were used to confirm the work function matching between Bi and Bi_(2)Ti_(2)O_(7)(BTO),ensuring the formation of an Ohmic junction.A Bi-Bi_(2)Ti_(2)O_(7)(B-BTO) composite was successfully synthesized via a one-step hydrothermal method,using bismuth nitrate and titanium sulfate as precursors.Compared to pure BTO,the B-BTO heterojunction,driven by dual electron injection from both metal Bi and BTO,significantly increased the ammonia synthesis rate to 686.95 μmol g^(-1)h^(-1),making it the most active nitrogen fixation material among similar pyrochlorebased catalysts to date.The differential charge density calculations,photocurrent(i-t) measurements,and photoluminescence(PL) tests further validate the role of Ohmic contacts in enhancing charge transfer and prolonging carrier lifetimes.This research provides valuable insight into the application of Ohmic junctions in photocatalytic nitrogen fixation and contributes to advancements in this field.展开更多
TiNb_(2)O_(7)represents an up-and-coming anode material for fast-charging lithium-ion batteries,but its practicalities are severely impeded by slow transfer rates of ionic and electronic especially at the low-temperat...TiNb_(2)O_(7)represents an up-and-coming anode material for fast-charging lithium-ion batteries,but its practicalities are severely impeded by slow transfer rates of ionic and electronic especially at the low-temperature conditions.Herein,we introduce crystallographic engineering to enhance structure stability and promote Li+diffusion kinetics of TiNb_(2)O_(7)(TNO).The density functional theory computation reveals that Ti^(4+)is replaced by Sb^(5+)and Nb^(5+)in crystal lattices,which can reduce the Li+diffusion impediment and improve electronic conductivity.Synchrotron radiation X-ray 3D nano-computed tomography and in situ X-ray diffraction measurement confirm the introduction of Sb/Nb alleviates volume expansion during lithiation and delithiation processes,contributing to enhancing structure stability.Extended X-ray absorption fine structure spectra results verify that crystallographic engineering also increases short Nb-O bond length in TNO-Sb/Nb.Accordingly,the TNO-Sb/Nb anode delivers an outstanding capacity retention rate of 89.8%at 10 C after 700 cycles and excellent rate performance(140.4 mAh g^(−1) at 20 C).Even at−30℃,TNO-Sb/Nb anode delivers a capacity of 102.6 mAh g^(−1) with little capacity degeneration for 500 cycles.This work provides guidance for the design of fast-charging batteries at low-temperature condition.展开更多
Direct regeneration is considered a sustainable solution to the issue of resource recycling and the environmental pollution caused by discarded lithium-ion batteries(LIBs).However,the direct regeneration of spent LiFe...Direct regeneration is considered a sustainable solution to the issue of resource recycling and the environmental pollution caused by discarded lithium-ion batteries(LIBs).However,the direct regeneration of spent LiFePO_(4)cathode materials still faces a formidable challenge that the irregular strains induced by the irreversible FePO_(4)phase after several charge and discharge cycles hinder the regenerative replenishment of Li^(+).This work proposes a lattice stress modulation strategy that reduces FePO_(4)phase into Fe_(2)P_(2)O_(7)phase(reduction of unit cell volume from 271.7 to 122.6Å^(3)),which releases the residual stress,paving continuous transport channels for Li^(+).In addition,the phase transformation reconstructs the FeO6 octahedra,significantly decreasing the migration energy barrier of ions within the lattice.Ultimately,the steric effect is synergistically weakened,facilitating the replenishment of Li^(+)and the elimination of Li-Fe anti-site defects.The regenerated LiFePO_(4)cathodes outperform commercial cathodes(80.2%capacity retention after 1000 cycles at 2 C).This work establishes fundamental principles for the pretreatment stage of the direct regeneration process and provides a paradigm shifting solution for sustainable LIBs recycling technology.展开更多
The limited redox capability of photocatalysts often leads to harmful NO_(2) byproduct formation during photocatalytic NO oxidation.Herein,Bi_(4)Ti_(3)O_(12) nanosheets modified with plasmonic metallic bismuth and abu...The limited redox capability of photocatalysts often leads to harmful NO_(2) byproduct formation during photocatalytic NO oxidation.Herein,Bi_(4)Ti_(3)O_(12) nanosheets modified with plasmonic metallic bismuth and abundant oxygen vacancies were synthesized via an in-situ reduction method.The optimized catalyst(BTOR2,with a molar ratio of 40%NaBH_(4) to Bi_(4)Ti_(3)O_(12))achieved a maximum NO removal efficiency of 62.3%,significantly higher than pristine Bi_(4)Ti_(3)O_(12)(40.5%) while minimizing NO_(2) production.The results reveal that the synergistic effects of Bi’s plasmonic resonance and oxygen vacancies enhanced visible light absorption and charge separation.The density functional theory(DFT)analysis showed electrons can transfer from Bi_(4)Ti_(3)O_(12)to Bi,promoting O_(2)activation to·O_(2)^(-)radicals.In-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)confirmed that light-induced H2O adsorption was strengthened,improving·OH radical generation.These radicals promoted the selective conversion of activated NO-to NO_(3)^(-),rather than NO_(2).This work provides valuable insights for advancing research into efficient photocatalysts for air pollution control.展开更多
文摘采用共沉淀法在不同母盐溶液浓度条件下合成出Gd_2Ti_2O_7:Ce纳米粒子;用XRD、SEM、TG-DTA等测试手段分析了样品的物相、形貌及发光性能;用热分析动力学计算不同升温速率下样品的活化能。结果表明:前驱体在升温过程的物相变化分3个阶段,用Doyle-Ozawa和Kissinger法分别对初始浓度为0.08和0.04 mol/L条件下各阶段表观活化能进行计算,其平均值为42.43、145.58、381.98 k J·mol^(-1)和51.28、161.51、446.30 k J·mol^(-1),晶粒生长活化能分别为12.58和19.54 k J·mol^(-1)。浓度为0.08 mol/L时,1173 K煅烧2 h制备出的纳米粒子表面活性较高,铈离子掺杂0.7%(摩尔分数)时发光强度最大。
基金Supported by Scientific and Technological Innovation of Shaanxi Provincial State-Owned Capital Operation Budget(2022-056)Institute's Self-Developed Technology Program(0801YK2317)+4 种基金Qin Chuangyuan Cites High-Level Innovation and Entrepreneurship Talent Program(QCYRCXM-2023-120)Qin Chuangyuan Industry Cluster Zone“Four Chains”Integration Program(2024CY-JJQ-46)National Natural Science Foundation of China(52071274)Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TBCs was designed based on the coefficient of thermal expansion and the coating functionality,and it was completed using atmospheric plasma spraying technique.The microstructure,mechanical properties,and thermal properties were analyzed.Results indicate that the adhesion of the prepared dual-layer composite TBCs is excellent,and no noticeable cracks appear at the interface.Compared with the MoSi_(2)coating with a low fracture toughness(0.88 MPa·m^(1/2)),the Gd_(2)Zr_(2)O_(7)coating exhibits higher fracture toughness(1.74 MPa·m^(1/2))and stronger resistance to crack propagation.The prepared MoSi_(2)-Gd_(2)Zr_(2)O_(7)composite coatings have a high porosity(39%),low thermal conductivity(1.020 W·(m·K)^(−1),1200℃),and low thermal diffusivity(0.249 mm^(2)/s,1200℃).Additionally,they possess a high oxygen-vacancy concentration,which ensures excellent insulation performance.
基金supported by the Natural Science Foundation of China (NSFC,No.52372212)。
文摘Photocatalysis uses solar energy to convert nitrogen and water directly into ammonia,helping reduce dependence on fossil fuels and offering a way to integrate the nitrogen cycle into a clean energy network.Ohmic junctions between metals and semiconductors have demonstrated significant advantages in enhancing stability and reducing carrier recombination,but their application in photocatalytic nitrogen fixation is limited due to the difficulty of work function matching and the complexity of fabrication processes.In this study,density functional theory(DFT) calculations were used to confirm the work function matching between Bi and Bi_(2)Ti_(2)O_(7)(BTO),ensuring the formation of an Ohmic junction.A Bi-Bi_(2)Ti_(2)O_(7)(B-BTO) composite was successfully synthesized via a one-step hydrothermal method,using bismuth nitrate and titanium sulfate as precursors.Compared to pure BTO,the B-BTO heterojunction,driven by dual electron injection from both metal Bi and BTO,significantly increased the ammonia synthesis rate to 686.95 μmol g^(-1)h^(-1),making it the most active nitrogen fixation material among similar pyrochlorebased catalysts to date.The differential charge density calculations,photocurrent(i-t) measurements,and photoluminescence(PL) tests further validate the role of Ohmic contacts in enhancing charge transfer and prolonging carrier lifetimes.This research provides valuable insight into the application of Ohmic junctions in photocatalytic nitrogen fixation and contributes to advancements in this field.
基金supported by the National Natural Science Foundation of China(22279026,2247090373)the Natural Science Foundation of Chongqing(CSTB2022NSCQ-MSX1401)+2 种基金the China Postdoctoral Science Foundation(2024M764198)the National Natural Science Foundation of China(22509044)the Fundamental Research Funds for the Central Universities(grant no.HIT.OCEF.2022017).
文摘TiNb_(2)O_(7)represents an up-and-coming anode material for fast-charging lithium-ion batteries,but its practicalities are severely impeded by slow transfer rates of ionic and electronic especially at the low-temperature conditions.Herein,we introduce crystallographic engineering to enhance structure stability and promote Li+diffusion kinetics of TiNb_(2)O_(7)(TNO).The density functional theory computation reveals that Ti^(4+)is replaced by Sb^(5+)and Nb^(5+)in crystal lattices,which can reduce the Li+diffusion impediment and improve electronic conductivity.Synchrotron radiation X-ray 3D nano-computed tomography and in situ X-ray diffraction measurement confirm the introduction of Sb/Nb alleviates volume expansion during lithiation and delithiation processes,contributing to enhancing structure stability.Extended X-ray absorption fine structure spectra results verify that crystallographic engineering also increases short Nb-O bond length in TNO-Sb/Nb.Accordingly,the TNO-Sb/Nb anode delivers an outstanding capacity retention rate of 89.8%at 10 C after 700 cycles and excellent rate performance(140.4 mAh g^(−1) at 20 C).Even at−30℃,TNO-Sb/Nb anode delivers a capacity of 102.6 mAh g^(−1) with little capacity degeneration for 500 cycles.This work provides guidance for the design of fast-charging batteries at low-temperature condition.
基金supported by the National Natural Science Foundation of China(52433002)Key projects of Shaanxi Province(2023GXLH-001)+2 种基金Key R&D Program of Shandong Province(2022TSGC2569)New Energy Material Innovation Consortium Projects of Yunnan Province(202302AB080018)Natural Science Basic Research Program of Shaanxi(2022TD-27)。
文摘Direct regeneration is considered a sustainable solution to the issue of resource recycling and the environmental pollution caused by discarded lithium-ion batteries(LIBs).However,the direct regeneration of spent LiFePO_(4)cathode materials still faces a formidable challenge that the irregular strains induced by the irreversible FePO_(4)phase after several charge and discharge cycles hinder the regenerative replenishment of Li^(+).This work proposes a lattice stress modulation strategy that reduces FePO_(4)phase into Fe_(2)P_(2)O_(7)phase(reduction of unit cell volume from 271.7 to 122.6Å^(3)),which releases the residual stress,paving continuous transport channels for Li^(+).In addition,the phase transformation reconstructs the FeO6 octahedra,significantly decreasing the migration energy barrier of ions within the lattice.Ultimately,the steric effect is synergistically weakened,facilitating the replenishment of Li^(+)and the elimination of Li-Fe anti-site defects.The regenerated LiFePO_(4)cathodes outperform commercial cathodes(80.2%capacity retention after 1000 cycles at 2 C).This work establishes fundamental principles for the pretreatment stage of the direct regeneration process and provides a paradigm shifting solution for sustainable LIBs recycling technology.
基金supported by the Natural Science Foundation of Chongqing(Nos.CSTB2024NSCQ-MSX1278,CSTB2023NSCQ-MSX0006)Technology Innovation Project of Shapingba District,Chongqing(No.2024004)+2 种基金Science and Technology Research Program of Chongqing Municipal Education Commission(Nos.KJZD-K202403102,KJQN202103110,KJQN202400512,KJQN202403107)National Natural Science Foundation of China(No.22406014)China Postdoctoral Science Foundation(No.2023MD744137).
文摘The limited redox capability of photocatalysts often leads to harmful NO_(2) byproduct formation during photocatalytic NO oxidation.Herein,Bi_(4)Ti_(3)O_(12) nanosheets modified with plasmonic metallic bismuth and abundant oxygen vacancies were synthesized via an in-situ reduction method.The optimized catalyst(BTOR2,with a molar ratio of 40%NaBH_(4) to Bi_(4)Ti_(3)O_(12))achieved a maximum NO removal efficiency of 62.3%,significantly higher than pristine Bi_(4)Ti_(3)O_(12)(40.5%) while minimizing NO_(2) production.The results reveal that the synergistic effects of Bi’s plasmonic resonance and oxygen vacancies enhanced visible light absorption and charge separation.The density functional theory(DFT)analysis showed electrons can transfer from Bi_(4)Ti_(3)O_(12)to Bi,promoting O_(2)activation to·O_(2)^(-)radicals.In-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)confirmed that light-induced H2O adsorption was strengthened,improving·OH radical generation.These radicals promoted the selective conversion of activated NO-to NO_(3)^(-),rather than NO_(2).This work provides valuable insights for advancing research into efficient photocatalysts for air pollution control.
