The Effect Of Tunable Graphene Oxide Sheet Size On The Structures And Properties Of Three Dimensional Graphene Sponge

By the look of graphene's development,it is of fundamental and practical significance to translate the novel physicochemical properties of individual graphene sheets into the macroscale by the assembly of graphene building blocks into macroscopic architectures with structural specialities and functional novelties.Graphene,reduced from graphene oxide(GO),can be well used as the building block for the preparation of grapheme based macroscopic materials.The lateral dimensions of GO sheets play an important role in determining the structures and properties of graphene-based macroscopic materials.The relationship between GO sheet size and the structures and properties of three dimensional grapheme(3DG)sponge was established.Then the catalytic properties and mechanical properties of 3DG sponge was researched by optimizing the three dimensional structure with uniform and controlled GO sheets.1.The preparation of controlled grapheme oxide sheets and the the relationship between sheet size and structure/catalytic property of 3DG spongeBased on the selective precipitation of GO sheets,three kinds of tunable GO sheets with narrow size distributions were prepared.Uniform GO sheets size would be narrowed and controlled by adjusting the time and speed of centrifugation.This size selection principle was used to investigate accurately the influence of tunable GO sheets size on dispersion,structure,and stacking behavior of GO sheets.SGO solution with more oxygen containing groups had higher solubility.LGO and MGO sponge had interconnected 3D porous network as imaged by SEM.GO sponge prepared by larger GO sheets had larger layer spacing with a lot of spaces.A cylinder was shown by LGO and MGO sponge and a obvious collapse of structure was exhibited by SGO sponge.Consequently,the macrostructure of resulting materials was strongly related to the GO sheets size.The 3DG sponge prepared with large,medium and small GO sheets also had differences both in specific surface area,structures and catalytic properties.The specific surface area increased with the growing GO sheets size,measured by the standard method of methylene blue absorption.3DG sponge showed clearly and relatively ordered pore structure.The pore size of 3DG sponge increased with the increasing dimension of GO sheets.The composite catalyst prepared with SGO solution had the best catalytic activity because of the highest loading and the smallest size distribution of Pt.The optimal catalytic activity was due to a lot of oxygen containing functional groups existing in SGO.2.The preparation of liquid crystals of controlled GOSs and the relationship between ordering and structure/mechanical property of 3DG spongeBase on the relationship between GO sheets size and the structures of 3DG sponge,the properties of 3DG sponge prepared by LGO was researched further.In the case of using uniform MGO and LGO,the nematic liquid crystals(LCs)phases are formed at low concentration.After chemical reduction,the LCs of GO solution are converted to 3DG sponges with a high degree of orientation,offering a new methodology to regulate the controlled large GO sheets.The orientation of GO solution can be inherited by 3DG sponge,making the sponge to have a large-scale ordered network structure.The network is strengthened by one more step-freeze drying before chemical reduction.The 3D elastic graphene sponges have low density and GOod elasticity,promising for the applications in strain sensing,shock damping,and energy cushioning.This work provides a new method for the preparation of 3DG materials constructed using the LCs of controlled large GO sheets and may shed new light on the relationship between the microstructures and mechanical properties of 3DG sponge.