Li_2Ni Ti O_4是一种岩盐结构的层状锂电正极材料,该材料能够嵌脱2个Li离子,首次充电比容量大,但不可逆容量也很大。本研究通过掺杂Mo元素,优化电化学性能,提高了可逆比容量。通过柠檬酸溶胶凝胶法,以Li NO_3、Ni(NO_3)_2·6H_2O和...Li_2Ni Ti O_4是一种岩盐结构的层状锂电正极材料,该材料能够嵌脱2个Li离子,首次充电比容量大,但不可逆容量也很大。本研究通过掺杂Mo元素,优化电化学性能,提高了可逆比容量。通过柠檬酸溶胶凝胶法,以Li NO_3、Ni(NO_3)_2·6H_2O和钛酸四丁酯为原料,以四水钼酸铵为钼源,合成了Li_2Ni Ti O_4和Li_(2.4)Ni_(0.67)Ti_(0.67)Mo_(0.26)O_4,可逆比容量从85 m Ah/g提高到162 m Ah/g,通过和炭黑复合,优化导电性,可逆比容量进一步提升到210 m Ah/g。展开更多
As a promising hydrogen storage material,the practical application of magnesium is obstructed by the stable thermodynamics and sluggish kinetics.In this paper,three kinds of NiTiO3catalysts with different mole ratio o...As a promising hydrogen storage material,the practical application of magnesium is obstructed by the stable thermodynamics and sluggish kinetics.In this paper,three kinds of NiTiO3catalysts with different mole ratio of Ni to Ti were successfully synthesized and doped into nanocrystalline Mg to improve its hydrogen storage properties.Experimental results indicated that all the Mg-NiTiO3composites showed prominent hydrogen storage performance.Especially,the Mg-NiTiO3/TiO2composite could take up hydrogen at room temperature and the apparent activation energy for hydrogen absorption was dramatically decreased from 69.8±1.2(nanocrystalline Mg)k J/mol to 34.2±0.2 k J/mol.In addition,the hydrogenated sample began to release hydrogen at about 193.2℃and eventually desorbed 6.6 wt%H2.The desorption enthalpy of the hydrogenated Mg-NiTiO3-C was estimated to be 78.6±0.8 k J/mol,5.3 k J/mol lower compared to 83.9±0.7 k J/mol of nanocrystalline Mg.Besides,the sample revealed splendid cyclic stability during 20 cycles.No obvious recession occurred in the absorption and desorption kinetics and only 0.3 wt%hydrogen capacity degradation was observed.Further structural analysis demonstrates that nanosizing and catalyst doping led to a synergistic effect on the enhanced hydrogen storage performance of Mg-NiTiO3-C composite,which might serve as a reference for future design of highly effective hydrogen storage materials.展开更多
A H_(2)O_(2)-modified layered titanate H_(1.07)Ti_(1.73)O_(4)(H_(2)O_(2)-HTO)is an excellent precursor for topochemical synthesis but its exfoliation reaction is unclear.Herein,we report the first study on the exfolia...A H_(2)O_(2)-modified layered titanate H_(1.07)Ti_(1.73)O_(4)(H_(2)O_(2)-HTO)is an excellent precursor for topochemical synthesis but its exfoliation reaction is unclear.Herein,we report the first study on the exfoliation reaction of H_(2)O_(2)-HTO and applications of H_(2)O_(2)-HTO and its nanosheets in the synthesis of NiTiO_(3)/TiO_(2) nanocomposites as anode materials for lithium-ion batteries(LIBs).H_(2)O_(2) in the interlayer space of H_(2)O_(2)-HTO can enhance ion-exchange capacity and exfoliation reaction kinetics.By reaction with Ni^(2+)solution,H_(2)O_(2)-HTO nanosheets were assembled into a HTO/Ni(OH)_(2) sandwich layered structurewhich could be transformed into a polycrystalline NiTiO_(3)/TiO_(2) nanocomposite with a sheetlike morphology and high NiTiO_(3) content by heattreatment.A mesocrystalline NiTiO_(3)/TiO_(2) nanocomposite with a plate-like morphology was obtained by heat-treatment of a Ni^(2+)-exchanged H_(2)O_(2)-HTO.The electrochemical results suggested that these NiTiO_(3)/TiO_(2) nanocomposites exhibit a synergistic effect of TiO_(2) and NiTiO_(3) for the enhanced reversible discharge–charge specific capacity as anode materials for LIBs.Furthermore,the NiTiO_(3) nanocrystals in the mesocrystalline NiTiO_(3)/TiO_(2) nanocomposite show a much larger capacity than those in the polycrystalline one due to the fast passage for the Li+migration in the mesocrystalline nanocomposite,namely the mesocrystalline effect.展开更多
Electrochemically stable nanostructured nickel titanate （NiTiO3） was prepared by sol-gel method and the structural and electrochemical properties were studied in the presence of H2SO4 ＋ CH3OH electrolyte. XRD and R...Electrochemically stable nanostructured nickel titanate （NiTiO3） was prepared by sol-gel method and the structural and electrochemical properties were studied in the presence of H2SO4 ＋ CH3OH electrolyte. XRD and Raman studies confirmed the single phase of NiTiO3 with the rhombohedral structure. Thermal stability was studied by TGA. Microstructure analysis by SEM confirmed the uniformly distributed spherical shaped NiTiO3 particles, and TEM studies showed the spherical shaped particles with an average size of 90 nm. The UV-Vis analysis shows the absorption spectrum of NiTiO3, while the FTIR spectrum showed the vibrations related to Ni-O and Ti-O stretching. Electrochemical tests were carried out by cyclic voltammetry （CV） and polarization studies. The CV measurements were made at room temperature as well as at 60℃： at room temperature, the NiTiO3 did not show any activity towards methanol oxidation whereas there observed an activity at the potential of 0.69 V at the operating temperature of 60℃. The ilmenite structured NiTiO3 has oxygen vacancies, most probably on the surface, which could have also contributed to the methanol oxidation. Thus the nanostructured NiTiO3 is proposed to be an active support material for metal electrocatalysts.展开更多
文摘Li_2Ni Ti O_4是一种岩盐结构的层状锂电正极材料,该材料能够嵌脱2个Li离子,首次充电比容量大,但不可逆容量也很大。本研究通过掺杂Mo元素,优化电化学性能,提高了可逆比容量。通过柠檬酸溶胶凝胶法,以Li NO_3、Ni(NO_3)_2·6H_2O和钛酸四丁酯为原料,以四水钼酸铵为钼源,合成了Li_2Ni Ti O_4和Li_(2.4)Ni_(0.67)Ti_(0.67)Mo_(0.26)O_4,可逆比容量从85 m Ah/g提高到162 m Ah/g,通过和炭黑复合,优化导电性,可逆比容量进一步提升到210 m Ah/g。
基金financial support from the National Natural Science Foundation of China(Grant No.51801078)the Natural Science Foundation of Jiangsu Province(Grant No.BK20180986)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(SJCX19_0614)。
文摘As a promising hydrogen storage material,the practical application of magnesium is obstructed by the stable thermodynamics and sluggish kinetics.In this paper,three kinds of NiTiO3catalysts with different mole ratio of Ni to Ti were successfully synthesized and doped into nanocrystalline Mg to improve its hydrogen storage properties.Experimental results indicated that all the Mg-NiTiO3composites showed prominent hydrogen storage performance.Especially,the Mg-NiTiO3/TiO2composite could take up hydrogen at room temperature and the apparent activation energy for hydrogen absorption was dramatically decreased from 69.8±1.2(nanocrystalline Mg)k J/mol to 34.2±0.2 k J/mol.In addition,the hydrogenated sample began to release hydrogen at about 193.2℃and eventually desorbed 6.6 wt%H2.The desorption enthalpy of the hydrogenated Mg-NiTiO3-C was estimated to be 78.6±0.8 k J/mol,5.3 k J/mol lower compared to 83.9±0.7 k J/mol of nanocrystalline Mg.Besides,the sample revealed splendid cyclic stability during 20 cycles.No obvious recession occurred in the absorption and desorption kinetics and only 0.3 wt%hydrogen capacity degradation was observed.Further structural analysis demonstrates that nanosizing and catalyst doping led to a synergistic effect on the enhanced hydrogen storage performance of Mg-NiTiO3-C composite,which might serve as a reference for future design of highly effective hydrogen storage materials.
基金supported by the Grants-in-Aid for Scientific Research(C)(No.21K04832)from the Japan Society for the Promotion of Sciencesponsored by the China Scholarship Council(CSC)(No.202008050202)for his study at Kagawa University.
文摘A H_(2)O_(2)-modified layered titanate H_(1.07)Ti_(1.73)O_(4)(H_(2)O_(2)-HTO)is an excellent precursor for topochemical synthesis but its exfoliation reaction is unclear.Herein,we report the first study on the exfoliation reaction of H_(2)O_(2)-HTO and applications of H_(2)O_(2)-HTO and its nanosheets in the synthesis of NiTiO_(3)/TiO_(2) nanocomposites as anode materials for lithium-ion batteries(LIBs).H_(2)O_(2) in the interlayer space of H_(2)O_(2)-HTO can enhance ion-exchange capacity and exfoliation reaction kinetics.By reaction with Ni^(2+)solution,H_(2)O_(2)-HTO nanosheets were assembled into a HTO/Ni(OH)_(2) sandwich layered structurewhich could be transformed into a polycrystalline NiTiO_(3)/TiO_(2) nanocomposite with a sheetlike morphology and high NiTiO_(3) content by heattreatment.A mesocrystalline NiTiO_(3)/TiO_(2) nanocomposite with a plate-like morphology was obtained by heat-treatment of a Ni^(2+)-exchanged H_(2)O_(2)-HTO.The electrochemical results suggested that these NiTiO_(3)/TiO_(2) nanocomposites exhibit a synergistic effect of TiO_(2) and NiTiO_(3) for the enhanced reversible discharge–charge specific capacity as anode materials for LIBs.Furthermore,the NiTiO_(3) nanocrystals in the mesocrystalline NiTiO_(3)/TiO_(2) nanocomposite show a much larger capacity than those in the polycrystalline one due to the fast passage for the Li+migration in the mesocrystalline nanocomposite,namely the mesocrystalline effect.
文摘Electrochemically stable nanostructured nickel titanate （NiTiO3） was prepared by sol-gel method and the structural and electrochemical properties were studied in the presence of H2SO4 ＋ CH3OH electrolyte. XRD and Raman studies confirmed the single phase of NiTiO3 with the rhombohedral structure. Thermal stability was studied by TGA. Microstructure analysis by SEM confirmed the uniformly distributed spherical shaped NiTiO3 particles, and TEM studies showed the spherical shaped particles with an average size of 90 nm. The UV-Vis analysis shows the absorption spectrum of NiTiO3, while the FTIR spectrum showed the vibrations related to Ni-O and Ti-O stretching. Electrochemical tests were carried out by cyclic voltammetry （CV） and polarization studies. The CV measurements were made at room temperature as well as at 60℃： at room temperature, the NiTiO3 did not show any activity towards methanol oxidation whereas there observed an activity at the potential of 0.69 V at the operating temperature of 60℃. The ilmenite structured NiTiO3 has oxygen vacancies, most probably on the surface, which could have also contributed to the methanol oxidation. Thus the nanostructured NiTiO3 is proposed to be an active support material for metal electrocatalysts.
