Spray Dried Cerium Oxide/Graphene/Polyaniline Composite for Supercapacitor Applications

Abstract

Supercapacitor materials can be broadly classified into three types: carbon based, metal oxide based and conductive polymers. Though, each of these materials has their own advantages, they also have unique drawbacks, like poor cycle life for conductive polymers, inherently low conductivity for most metal oxides and low energy density for carbon based material. In the study, a composite of these three materials is synthesized through an easily scalable process to yield a supercapacitor material with high specific capacitance, excellent rate capability and cycle life. Micron sized cerium oxide (CeO 2 )/graphene/polyaniline (PANI) composites are synthesized using spray-drying and chemical reduction. First, graphene oxide/PANI composites are prepared by an in-situ polymerization technique. A hydrothermally one-step process is used synthesized CeO 2 nanoparticles. These raw materials are then thoroughly mixed through ultrasonication and spray dried at 200°C. The use of PANI has two benefits. One, it acts as a binder between the inorganic CeO 2 nanoparticles and GO during the spray dried process to yield micron sized spherical particles. Second, PANI also forms a uniform highly conductive layer, which boosts the electronic transmission and thereby the supercapacitance of the composite. The CeO 2 improves the poor cycle life of PANI. The random stacking and agglomerating of GO and CeO 2 during the spray drying process produces numerous channels which acts as pathways for the electrolytic ions. Thus the individual elements work synergistically to improve the supercapacitor performance. The synthesized composites have been structurally characterized using XRD, FTIR and SEM. The electrochemical properties have been evaluated in standard three-electrode set-up with 3M KOH electrolyte using cyclic voltammetry, galvanostatic charge discharge curves and impedance analysis. The results from the electrochemical analysis show that the spray dried composite material show high specific capacitance, energy density and long cycle life.