| Polyoxometalates(POMs), which are nanoscale transition metal-oxygen clusters,have received considerable attention in recent years due to their structural diversity,outstanding redox properties,electron and proton transfer/storage abilities, thermal stability, solubility and lability of their lattice oxygen. As a two-dimensional monolayer nano-materials of sp2-bonded carbon atoms, graphene with its large surface area and unparalleled electrical characteristics,have been employed in electrochemical,energy conversion and storage and electronics and so on. Composites based on polyoxometalates(POMs) and graphene have attracted widespread attention as they combine the unique chemical reactivity with the structural features to realize the synergistic effect of the nanohybrids.The composites have shown great potential in energy conversion and storage, sensor devices, adsorption, catalysis, aerospace and other fields of cutting-edge technologies.In this thesis, we report a rational design and the synthesis of POM(H4[PMo11VO40]·32.5H2O)-coupled reduced graphene oxide(RGO) through a simple anion exchange in which a polymeric ionic liquid(PIL), poly(1-vinyl-3-ethylimidazolium bromide), is employed as a linker to bridge two components. The POM/PIL/RGO materials were further characterized by scanning electron microscopy,transmission electron microscopy, FT-IR and thermogravimetric analyses. The resulting materials were employed as electrode materials for Supercapacitors(SCs),the specific capacitance of the PIL-15% are 208 F/g, which is two-fold higher than that of POM/RGO electrode(106 F/g). The adoption of PIL enables a uniform distribution of discrete POM molecules over the high surface area of the RGO and improved electrochemical performance of the composites. As a result, POM or PIL contents and drying method influence the capacitive behavior of the POM/PIL/RGO electrode. As the POM contents decrease, the capacitance of the composite PIL-15%-1, POM-55% and POM-35% increase gradually; the capacitance of the composite PIL-15%, PIL-10%, PIL-5% and PIL-15%-1, PIL-10%-1, PIL-5%-1increase first, then decrease. Vacuum-driedcan enhance significantly electrochemicalperformance of the composites compared to freeze-dried. From this data, the optimized composition of PIL was chosen to be 10% of the GO’s mass, and the specific capacitances reach 243 F/g, representing one time improvement over that of the supercapacitor made from pure graphene electrodes(117 F/g). |
