In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles a...In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles are studied by soft x-ray absorption spectroscopy in total electron（TEY） and fluorescence（TFY） detection modes, which provide surface and bulk information, respectively. The spectra of Co L2,3-edge indicate that Co contributes to charge compensation below 4.4 V.Combining with the spectra of O K-edge, it manifests that only O contributes to electron compensation above 4.4 V with the formation of local O 2 p holes both on the surface and in the bulk, where the surficial O evolves more remarkably. The evolution of the O 2 p holes gives an explanation to the origin of O2^-or even O2. A comparison between the TEY and TFY of O K-edge spectra of LiCoO2 cycled in a range from 3 V to 4.6 V indicates both the structural change in the bulk and aggregation of lithium salts on the electrode surface are responsible for the capacity fading. However, the latter is found to play a more important role after many cycles.展开更多
We report a study of the roles of gadolinium(lll)(Gd3+)dopants in influencing the catalytic activity of gadolinium-doped ceria nanoparticles towards the pro-oxidation of hydrogen peroxide to hydroxyl radicals.These do...We report a study of the roles of gadolinium(lll)(Gd3+)dopants in influencing the catalytic activity of gadolinium-doped ceria nanoparticles towards the pro-oxidation of hydrogen peroxide to hydroxyl radicals.These doped ceria nanoparticles with dopant concentrations of 0.6 wt.%,3 wt.%,and 6 wt.%Gd^3+were synthesized using an ozone-mediated method for tuning their catalytic activities.The Gd dopants were found to foster an increase in the percentage of Ce^3+ions in the doped ceria nanoparticles.Our reaction kinetic study revealed that the relationship between the overall reaction rates and the Gd dopant concentrations in our doped materials followed a volcano-like trend.In contrast,the apparent activation energy values of these Gd-doped ceria nanoparticles were found to be positively associated with the concentrations of Gd dopants.The overall catalytic activity trend was attributed to the interplay between the promotion and degradation effects of the Gd dopants on the properties of doped ceria nanoparticles.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21503263,U1632269,21473235,and 11227902)
文摘In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles are studied by soft x-ray absorption spectroscopy in total electron（TEY） and fluorescence（TFY） detection modes, which provide surface and bulk information, respectively. The spectra of Co L2,3-edge indicate that Co contributes to charge compensation below 4.4 V.Combining with the spectra of O K-edge, it manifests that only O contributes to electron compensation above 4.4 V with the formation of local O 2 p holes both on the surface and in the bulk, where the surficial O evolves more remarkably. The evolution of the O 2 p holes gives an explanation to the origin of O2^-or even O2. A comparison between the TEY and TFY of O K-edge spectra of LiCoO2 cycled in a range from 3 V to 4.6 V indicates both the structural change in the bulk and aggregation of lithium salts on the electrode surface are responsible for the capacity fading. However, the latter is found to play a more important role after many cycles.
基金C.L.C.,A.B.,and T.J.F.gratefully acknowledge the financial support from the National Science Foundation(No.CHE-1362916)Y.G.and D.W.Z.were supported by the CASShanghai Science Research Center(No.CAS-SSRC-YJ-2015-01)the National Natural Science Foundation of China(Nos.11574340 and 21773287).
文摘We report a study of the roles of gadolinium(lll)(Gd3+)dopants in influencing the catalytic activity of gadolinium-doped ceria nanoparticles towards the pro-oxidation of hydrogen peroxide to hydroxyl radicals.These doped ceria nanoparticles with dopant concentrations of 0.6 wt.%,3 wt.%,and 6 wt.%Gd^3+were synthesized using an ozone-mediated method for tuning their catalytic activities.The Gd dopants were found to foster an increase in the percentage of Ce^3+ions in the doped ceria nanoparticles.Our reaction kinetic study revealed that the relationship between the overall reaction rates and the Gd dopant concentrations in our doped materials followed a volcano-like trend.In contrast,the apparent activation energy values of these Gd-doped ceria nanoparticles were found to be positively associated with the concentrations of Gd dopants.The overall catalytic activity trend was attributed to the interplay between the promotion and degradation effects of the Gd dopants on the properties of doped ceria nanoparticles.
