Preparation Of Graphene By Liquid Exfoliation Method And Its Application In Electrochemistry

Graphene,as the newest form of carbon nanomaterials,has attracted great attention in a wide range of applications,owing to its excellent mechanical,electrical,optical and thermal properties.However,no practical methods were achieved for massive producing high-quality graphene to date.Liquid-phase exfoliation of graphite provides a promising approach to produce defect-free,unoxidized graphene.It was unfortunately that rather low exfoliation efficiency presented when only pure solvents,such as NMP?DMF?DMSO,were used as exfoliation medium.In this thesis,we developed a new approach to improve exfoliation efficiency dramatically using several cheap organic salts as efficient and universal assistants.Charge/electron transfer behaviours of as-obtained graphene as well as its composites were investigated.Such obtained high-quality graphene were then applied in the fields of supercapacitors and electrocatalysis on alcohol electro-oxidation.The contents of the thesis are given as follows:1,Four types of common organic salts,i.e,,potassium sodium tartrate,sodium tartrate,sodium citrate and edetate disodium were used as assistants for various exfoliation medium,including NMP?DMF?DMSO?IPA and so on.Obviously improvement on exfoliation efficiency for all these solvents was demonstrated.Physical characterizations such as TEM,SAED,FTIR,Raman,EDX,AFM,TGA,UV-Vis,and electrochemical studies shown that graphene flakes were successfully obtained,and the graphene nanosheets have perfect conjugated ?-bonding system,clean surfaces and are free of doped heteroatoms?2,The good charge transfer performance of PG was tested?Furthermore,a simple and excellent carbon-based electrode material with very fast charge transfer performance based on PG hybridized with GO was prepared.Electrode made of such GO/PG composite shows Nernstien behavior and very fast charge-transfer kinetics for electrochemical reactions of Fe(CN)63-/4-.This electrochemical performance can be comparable to that of multiwalled CNT reported in literature.The enhancement of charge transfer in GO/PG can be explained by unique inner sphere reaction mechanism originated from acetylacetone-like structures of GO alonging with PG patched ? conjugation systems of GO.3,Pristine graphene(PG)prepared by organic salt-assisted liquid-phase exfoliation of graphite in DMSO was used as a catalyst support of palladium nanoparticles(PdNPs).PdNPs with a unified diameter of about 4 nm were loaded on such PG sheets through simply reducing palladium acetate with NaBH4 in organic solvent system.The obtained Pd/PG catalyst exhibited an excellent activity(the more negative offset potential and anodic peak potential)for the extrooxidation of alcohol in 1 M NaOH electrolyte.The enhanced electrochemical activity of Pd-NPs/PG catalyst toward alcohol oxidation can be mainly ascribed to PG's enhanced conductivity originated from its defect-free basal plane.On the other hand,Water-processable PG/GO composites were prepared through mixing PG/DMSO dispersion and GO/H2O suspension.The PG/GO composites were then modified on glassy carbon electrode for testing their capacitive performance.Improved capacitive properties and better cyclability were observed comparing to individual components,owing to effectively utilizing the pseudo-capacitive and good wetting properties of GO component,and the excellent electrical conductivity and good cyclability of PG component.