Polymer electrolyte membrane fuel cells (PEMFC) are one of the most efficient energy conversion systems for portable, stationary and automotive applications. In spite of the tremendous progress in PEMFC in terms of research and applications, there are still significant barriers to their commercialization mainly due to high cost of Pt catalyst and durability issues. Additionally, the sluggish oxygen reduction reaction (ORR) is another problem of PEMFC. Platinum (Pt) nanoparticles extensively used as catalyst in PEMFC have not only high cost and performance problems but also have low abundance. The electrocatalytic activities of the Pt based catalysts depend on several parameters such as catalyst support, catalyst preparation technique, accessibility of the metal on the support, and testing conditions. Catalyst support materials are of great importance in regulating the properties of catalyst nanoparticles such as shape, size, and dispersion. Carbon black, the most commonly used commercial catalyst support, has several limitations which cause the degradation of catalyst activity and performance. Graphene is an increasingly important material with distinct properties such as high electrical conductivity, high contact surface area and enormous stability. Here we aim to use of graphene and its hybrids as the catalyst support in PEMFC due to their high surface area, high conductivity and chemical stability [1]. In this regard, graphene nanoplatelets, reduced graphene oxide, functionalized graphenes and graphene based hybrids. Graphene based hybrid supports were prepared by mechanical mixing of graphene at varying ratios of other carbon materials including carbon black (CB), CNT, carbon nanopowder (CNP) and carbon nanofibers. Graphene supported Pt nanoparticles were prepared by means of impregnation-reduction, supercritical carbon dioxide deposition, electrospinning/electrospraying, electrophoresis and photodeposition. Highly dispersed and uniformly decorated Pt nanoparticles with a small particle size (1-2 nm) were obtained. Moreover, remarkably enhanced electrocatalytic activity for oxygen reduction reactions and fuel cell performances for graphene based hybrids were achieved [1-3]. Best results in terms of electrocatalytic activity towards oxygen reduction reaction, fuel cell performance and power output were obtained with Pt/GO-CNT, Pt/GO-CB and Pt/GO-CNP hybrid catalysts. It seems that carbon materials added to graphene effectively modify the array of graphene and provide synergistic effect.

Acknowledgements

The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 696656 (Graphene Flagship)

References

1. Quesnel et al., 2D Mater., 2017, 2, 030204.
2. Daş, S. Alkan Gürsel, L. Işikel Şanli, A. Bayrakçeken Yurtcan, Int. J. Hydrogen Energy,2017, 42, 19246.
3. Işıkel Şanlı, V. Bayram, S. Ghobadi, N. Düzen, S. Alkan Gürsel, Int. J. Hydrogen Energy, 2017, 42,1085.