Controllable Electrochemical Preparation Of Graphene/Polyaniline Composite

Owing to graphene’s unique properties such as superior electrical conductivity,excellent mechanical flexibility, large surface area, and high thermal and chemicalstability, the development of graphene based functional composites are attractingintense interest, of which graphene/conducting polymers (graphene/CPs) hasreceived much attention. The graphene/CPs material is typically prepared through insitu polymerizing the monomers in a graphene suspension, where the graphene ispre prepared by chemical reduction of graphene oxide (GO) obtained from ultrasonicexfoliation of oxidized graphite. Alterative methods include polymerizing themonomers in a GO dispersion followed by chemical reduction of GO,(electro)polymerizing aniline on a graphene paper, and direct solution phase mixingof CPs and graphene. In all the cases, the graphene and CPs are prepared step by step,which is time consuming. Additionally, the chemical reduction of GO usually requiretoxic reductants, and also, conventional chemical polymerization of aniline inducesimpurities which decrease the inherent properties of the materials. Thus, searching forsimple, fast,“green”, and scalable methods to “clean” graphene/PANI composites ishighly desirable.Herein, we report one step synthesis of graphene/PANI composite byelectrodeposition technique. Electrochemical deposition is such a method that hasmany advantages, such as simpleness, speediness, environmental benignity, scalablity,and moreover controllability.Details are shown as follows:(1) Preparation of GO aniline solution: The one pot electrochemical synthesisof graphene/PANI from GO and aniline requires that GO and aniline form a stabledispersion. Therefore, to achieve the electrochemical synthesis, the dispersity ofoxidized graphite, in the presence of aniline was first examined at pH1.012.0. Wealso discussed the reason for the pH dependent stability of GO in the presence ofaniline.(2) One Step Electrochemical Synthesis of Graphene/Polyaniline CompositeFilms: electrodeposition synthesis of graphene/PANI composite films by cyclicvoltammetric (CV) electrolysis with a stable dispersion of GO and aniline, alternatelayered graphene–PANI films are obtained, with the topmost layer being PANI particles (LP) or graphene sheets(LG) just by changing the initial scan directions.(3) Structural Characterization: Evidences for the two graphene PANI bilayerswere directly obtained from scanning electron microscopy(SEM) and cross sections、Transmission electron microscopy(TEM). Raman spectroscopy was used to determinethe microstructures of LPand LG. Interestingly, a difference in Raman spectra isobserved between LPand LG: LPshows more distinct spectrum features of polyanilinethan LG.(4) Electrical and electrochemical properties Characterization: electrochemicalimpedance spectroscopy (EIS) revealed a significant difference in charge transferresistance between LGand LPin a neutral medium. Nevertheless, LGshows itsconductivity higher than that of LP. Also, We found that as the film thicknessincreased, charge transfer in LGand LPchanged little. It is thus suggested that thetopmost layer that directly communicates with the electrolyte plays a key role for thecharge transfer. Also, the electrochemical activity of graphene/PANI composites wasinvestigated by cyclic voltammetry. The obtained graphene/PANI composite filmsshow high electrical conductivity and electroactivity in acidic and even in neutral andalkaline media. In comparison, LGshows its electrical and electrochemical behaviorsbetter than that of LP.In conclusion, we have developed a simple electrochemical route forgraphene/PANI composites and particularly unveiled two types of LbL structures inthe composite films, as well as revealed their excellent but different electrical andelectrochemical properties. We believe that the proposed method opens a way toone step synthesize graphene/polymer composites, not just graphene/PANI, and couldbe developed as a universal method for layered assemblies. The resultinggraphene based layered composite materials, with variable functional spacers,controllable surfaces, and2D cavities, are unique, which have great potential invarious applications such as sensors, catalysis, and energy source systems.