Fabrication Of Metal Phthalocyanine/Graphene Composites And Their Application For Oxygen Reduction

Over the past few years, the rapid development of renewable energy has increased the need for sustainable energy storage technologies in order to address the challenges of increasing energy demand and the cyclic nature of renewable energy sources. Direct methanol fuel cells(DMFCs) are promising technologies for portable electronics applications. The oxygen reduction reaction(ORR) at the cathode is of great importance for the overall performance of fuel cells. However, Pt-based materials, the best and most effectively used catalysts for ORR to date, have present major challenges hindering DMFCs from widespread commercial application. These challenges include the catalysts,high price, scarcity, poor tolerance to crossover effect, and especially slow kinetics of the oxygen-reduction reaction(ORR). Therefore, it is eagerly necessary to develop new nonprecious-metal electrocatalysts with high activity, practical durability, insensitive methanol-tolerance, and low cost. In this dissertation, two metal macrocycles/graphene composite catalysts,(2,5-bis(3,4-dicyanophenyl) aminopyridine iron( ?) polyphthalocyanine/grapheme and 2,5-bis(3,4-dicyanophenyl) aminopyridine cobalt( ?) polyphthalocyanine/grapheme, marked as PFePc/Gr and PCoPc/Gr respectively), have been successfully synthesized by a solvothermally assisted ?–? assembling method. The morphology of the as-prepared was characterized using scanning electron microscopy(SEM), transmission electron microscopy(TEM). The ?–? interaction between polyphthalocyanine and graphene was conformed by Ultraviolete visible(UV-vis) spectroscopy, Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS). The electrocatalytic activity of the hybrid composites for ORR was evaluated by Cyclic voltammetry(CV), rotating disk electrode(RDE), rotating ring-disk electrode(RRDE) and chronoamperometric measurements. The experimental results show that, the obtained composites exhibited relatively better electrocatalytic performance towards the ORR in alkaline media, such as more positive onset potential and half wave potential, larger limiting current, and higher value of electron transfer number, which catalyze oxygen to H2 O via a nearly direct four-electron transfer pathway. In addition, the as-prepared catalysts possess good tolerance to methanol crossover and high stability, comparable to the commercial Pt/C catalyst. The improvement in catalytic acticity could be ascribed to fast electron transfer rate of Gr and the synergistic effect between the polyphthalocyanine moieties and the Gr sheets.