Modification And Application Of Chemical Vapor Deposition Growth Graphene

As a two-dimensional material with zero band gap,graphene has excellent optical,electrical,mechanical and thermal properties and has a wide application prospect.Among various graphene materials,the graphene film prepared by the chemical vapor deposition(CVD)has the advantages of large area,high quality,controllable number of layers,and is closer to perfect graphene,and can be used as a raw material for electronic devices.However,the zero-gap property of graphene makes itself insufficiently applicable in the semiconductor industry,and the chemical inertness of graphene due to its robust structure is suitable to chemical-related applications.Modification of CVD graphene is an effective way to increase its application flexibity.The main methods for the modification of CVD graphene are substitution doping,covalent,non-covalent modification and so on.In the research,we modified the surface of CVD graphene by mildly O2 plasma,and then hydrothermally grew a layer of platinum nanoparticles with approximately uniform size on the film.Due to the single layer characteristics of CVD graphene,the mass loading of Pt in the Pt NPs/CVD graphene composite film is higher than 80 wt.%,which is much higher than that of the conventional Pt/C catalyst(20 wt.%).At the same time,the ultra-thin hybrid films we obtained can be transferred to any substrates like CVD graphene for a variety of applications.Electrochemical testing of methanol oxidation reaction(MOR)is accomplished by transferring the sample to a glassy carbon electrode,exhibiting an ultra-high electrochemically active surface area(ECSA)and efficient MOR activity.By further depositing Ru onto the Pt NPs/Graphene surface the current density of the PtRu/CVD graphene catalyst film in methanol oxidation is increased by 2.5 times at the Ru coverage about 32%,and shows 0.20 V lower over-potential at the onset for MOR.We believe that the excellent conductivity of CVD graphene and the preferred orientation of fcc(100)of Pt NPs modified on the surface of CVD graphene and the good dispersion of Ru and Pt are the reasons for the improved MOR activity.According to our statistics of Pt NPs with a diameter of about 3 nm,the ECSA and mass specific current density of Pt in the sample are superior to most Pt-based nanostructures.According to the experimental and simulation results in the early literatures,the surface of the two-layer or multi-layer graphene can be covalently modified by functional groups(hydrogen,hydroxyl,etc.)to facilitate the conversion of sp2 into sp3 hybridization bonds between graphene layers.Wec all this continuous single layer diamond film from multilayer graphene“diamane”.We used diamond anvil cells to press the suspended CVD bilayer graphene obtained by transfer onto Au grids,used water as pressure transmitting medium(PTM),and characterized it by in-situ Raman spectroscopy.We obtained evidence of formation of diamane through the evolution of the G-band of the Raman spectrum with pressure changes.When silicone oil was used as the PTM,Raman spectroscopy showed no significant change in the structure,demonstrating that water plays an important role in it.Among them,the CVD double-layer graphene is attached with a hydroxyl group or a hydrogen group on the surface in a high-pressure-inducing manner,so that water provides the necessary group coverage,and the double-layer graphene layer is bonded to form a diamane.