Graphene is a competitive electrode material for supercapacitors due to its unique two-dimensional structure,large surface area,high conductivity,and good physicochemical stability.However,random agglomeration and res...Graphene is a competitive electrode material for supercapacitors due to its unique two-dimensional structure,large surface area,high conductivity,and good physicochemical stability.However,random agglomeration and restacking of graphene sheets result in a reduced surface area and a loose structure with low density,which severely restricts the application for high gravimetric/volumetric energy density devices.Rational design of the layered-stacking structure of graphene assemblies can effectively prevent the restacking of graphene sheets,construct efficient ion transport channels,and improve spatial utilization,demonstrating the huge potential for developing advanced electrode materials.Herein,from the aspect of improving the electrochemical kinetics through designing efficient electron and ion transport paths,we first highlight the advantages of layered-stacking graphene assemblies,describe some common routes for preparing graphene building units,and then summarize the novel methods to design layered-stacking structures.A comprehensive review of the typical structure including nanocarbon pillared graphene,porous graphene blocks,and graphene ribbon films is provided with a focus on the mechanisms behind the performance improvements.Finally,critical challenges and some general ideas for future development are proposed,which may open up new opportunities for material chemistry and device innovation.展开更多
Hierarchical layer-stacking Mn-Ce composite oxide with mesoporous structure was firstly prepared by a simple precipitation/decomposition procedure with oxalate precursor and the complete catalytic oxidation of VOCs(b...Hierarchical layer-stacking Mn-Ce composite oxide with mesoporous structure was firstly prepared by a simple precipitation/decomposition procedure with oxalate precursor and the complete catalytic oxidation of VOCs(benzene, toluene and ethyl acetate) were examined. The Mn-Ce oxalate precursor was obtained from metal salt and oxalic acid without any additives. The resulting materials were characterized by X-ray diffraction(XRD), Brunauer-Emmett-Teller(BET), scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDX), hydrogen temperature programmed reduction(H2-TPR) and X-ray photoelectron spectroscopy(XPS). Compared with Mn-Ce composite oxide synthesized through a traditional method(Na2CO3 route), the hierarchical layer-stacking Mn-Ce composite oxide exhibited higher catalytic activity in the complete oxidation of volatile organic compounds(VOCs). By means of testing, the data revealed that the hierarchical layer-stacking Mn-Ce composite oxide possessed superior physiochemical properties such as good low-temperature reducibility, high manganese oxidation state and rich adsorbed surface oxygen species which resulted in the enhancement of catalytic abilities.展开更多
基金This work was supported by the National Natural Science Foundation of China(Nos.51972342,51872056,and 52062046)Taishan Scholar Project of Shandong Province(ts20190922)+1 种基金Key Basic Research Projects of Natural Science Foundation of Shandong province(ZR2019ZD51)the Natural Science Foundation of Xinjiang Autonomous Region(2020D01C019).
文摘Graphene is a competitive electrode material for supercapacitors due to its unique two-dimensional structure,large surface area,high conductivity,and good physicochemical stability.However,random agglomeration and restacking of graphene sheets result in a reduced surface area and a loose structure with low density,which severely restricts the application for high gravimetric/volumetric energy density devices.Rational design of the layered-stacking structure of graphene assemblies can effectively prevent the restacking of graphene sheets,construct efficient ion transport channels,and improve spatial utilization,demonstrating the huge potential for developing advanced electrode materials.Herein,from the aspect of improving the electrochemical kinetics through designing efficient electron and ion transport paths,we first highlight the advantages of layered-stacking graphene assemblies,describe some common routes for preparing graphene building units,and then summarize the novel methods to design layered-stacking structures.A comprehensive review of the typical structure including nanocarbon pillared graphene,porous graphene blocks,and graphene ribbon films is provided with a focus on the mechanisms behind the performance improvements.Finally,critical challenges and some general ideas for future development are proposed,which may open up new opportunities for material chemistry and device innovation.
基金supported by Strategic Project of Science and Technology of Chinese Academy of Sciences(XDB05050000)the National Natural Science Foundation of China(51272253)
文摘Hierarchical layer-stacking Mn-Ce composite oxide with mesoporous structure was firstly prepared by a simple precipitation/decomposition procedure with oxalate precursor and the complete catalytic oxidation of VOCs(benzene, toluene and ethyl acetate) were examined. The Mn-Ce oxalate precursor was obtained from metal salt and oxalic acid without any additives. The resulting materials were characterized by X-ray diffraction(XRD), Brunauer-Emmett-Teller(BET), scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDX), hydrogen temperature programmed reduction(H2-TPR) and X-ray photoelectron spectroscopy(XPS). Compared with Mn-Ce composite oxide synthesized through a traditional method(Na2CO3 route), the hierarchical layer-stacking Mn-Ce composite oxide exhibited higher catalytic activity in the complete oxidation of volatile organic compounds(VOCs). By means of testing, the data revealed that the hierarchical layer-stacking Mn-Ce composite oxide possessed superior physiochemical properties such as good low-temperature reducibility, high manganese oxidation state and rich adsorbed surface oxygen species which resulted in the enhancement of catalytic abilities.