Graphene /TiO2 Composite Electrode: Synthesis and Application towards the Oxygen Reduction Reaction

A graphene oxide (GO) was prepared from a commercial graphite nano-crystals using Hummers' method. Later, GO powder was reduced either by placing it under a H2 gas flow in a controlled gas reactor at 450 oC or using a hydrazine hydrate solution (HH) in a 1000-Watt microwave oven. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction patterns (XRD) confirmed that both of the oxidation and reduction processes of graphite and GO powders, respectively, were incomplete. Also, the surface area of the H2 gas - reduced GO powder was found to be higher than the case where HH was used to reduce the same powder. Fourier transform infrared spectroscopy (FT-IR) and XPS have revealed that GO surface consists mainly of hydroxyl, epoxy, carbonyl and carboxylic groups. The electrocatalytic properties of (i) glassy carbon (GC), (ii) commercial TiO2 (P25-TiO2/GC), (iii) TiO2-supported GO (GO/TiO2/GC), (iv) TiO2 - supported HH - reduced GO (HHRGO/TiO2/GC) and (v) TiO2 - supported H2 gas - reduced GO (H2RGO/TiO2/GC) electrodes towards the oxygen reduction reaction (ORR) in acidic solution in presence and absence of UV radiation were examined. The results have shown that the H2RGO/TiO2/GC electrode has the best electrocatalytic activity in terms of current at a certain potential but glassy carbon electrode (GC) was found to be the best in terms of the onset potential of the ORR.