Polyoxometalates-Graphene oxide Hybrids : Synthesis, Structure and Electrochemical applications

Abstract

The deposition of POM on chemically reduced graphene oxide sheets was carried out through electron transfer interaction and electrostatic interaction between POM and graphene sheets to make heterogeneous catalyst in aqueous media. Well dispersed individual PMo clusters were observed by the electron microscopy and atomic force microscopy measurements. The interaction between polyoxometalate and the graphene oxide sheet was confirmed by using various spectroscopic methods such as FT-IR, UV-VIS, and Raman. The UV-Visible, IR and cyclic voltammetry results revealed the alteration of electronic structure of deposit-ed PMo as a result of strong interaction with the graphene surface. Electrochemical properties of PMo-rGO catalyst was investigated in an aqueous acidic electrolyte. The hybrid catalyst showed enhanced electro-oxidation of nitrite compared with pure homogeneous PMo and rGO. Further, POMs were investigated for high proton conductive membranes composited with Nafion for polymer electrolyte membrane fuel cell (PEMFC) under low relative humidity. (The investment of POMs is performed to contain lots of water molecules through hydrogen bond.) POMs were immobilized by modified graphene oxide to prevent it from leaching out during operation. A Nafion/PW-mGO composite membrane provided high amount of bound water so that the proton conductivity was shown higher than Nafion 212 membrane. Fuel cell performance of Nafion/PW-mGO composite membrane exhibited the higher power density of 841 mW cm -2, operating at a temperature of 80 °C under 18% RH in contrast with Nafion 212 and recast Nafion, operating under identical conditions, a peak power density of 210 mW cm-2 and 208 mW mW mW cm -2 were observed. The composite membrane could be a potential membrane for fuel cell operating under low relative humidity. ⓒ 2014 DGIST