The Fabrication And Properties Of Ultra-flexible Porous Graphene Films

Due to its particular crystal structure,graphene has a great specific surface area,and excellent mechanical properties,electrical and thermal conductivity,which makes it an attractive material.As an important form of macro assembly materials of graphene,flexible graphene films keep the excellent properties of single layer graphene well,which makes it a broad application in energy storage materials,electromagnetic shielding materials,thermal conductive materials,sensors and so on.Developing a flexible and foldable graphene films are of overreaching importance to meet the requirements of modern society for flexible materials.Nowadays,the fabrication of graphene films can be generalized into two categories:One is directly constructing films from graphene sheets,and the other is to reduce graphene oxide(GO)films.The former,mainly on physical processing,and the obtained graphene films always show poor mechanical properties.Although the present flexible graphene films could be bent,but mostly could not be folded or folded with plastic deformation even breaking.Meanwhile,most of graphene films stacked together compactly with lamellar structure which damaged to its applications in energy storage.Herein,inspired by the voids toughening of polymer,a pristine graphene porous film with ultra-flexibility was prepared via a simple reduction and leavening treatment of GO film.The detail works are as follows:Firstly,we use alumina ceramic chips as clamps to apply a force along the thickness direction of GO films,which limit the expansion of graphene films during the hydrazine hydrate reduction process.The obtained porous graphene films have smooth surfaces,and can be double folded or crumbled like polymer films and papers,but quickly recovered to the initial shapes without plastic deformations or creases.Moreover,by coating reducing regents on the surfaces of the films can decrease the usage of the toxic regents which pollute the environment.Secondly,when used the free standing ultra-flexible reduced graphene oxide(UFRGO)films as the electrodes of supercapacitors,any other conductive agents or adhesives are used.The supercapacitor can be double folded without any loss in energy density.The results of three electrodes electrochemical test system certified that the UFRGO films can be used in energy storage with excellent cycle stability.In addition,by a simple filling of the graphene films with phase change materials,the composite films can be used as shape memory like materials.Finally,we further add the single layers molybdenum disulfide(MoS2)to GO solutions to fabricate the MoS2/GO composite films,and through the above reduction method,flexible MoS2/RGO composite films with honeycomb holes are made.The flexible composite films can be folded without breaking,and can be used as the electrodes of flexible supercapacitors.