Platinum Supported on Electrochemically-Exfoliated Graphene Oxide As a Catalyst for Improving the Performance of the Hydrogen Fuel Cell

Abstract

With the increasing contamination and depletion problems of fossil fuel, an alternative technology, the proton exchange membrane fuel cells (PEMFCs), has been considered as the most promising power source of the future in the field of the portable electrics and vehicles. The hydrogen fuel cell is expected to be the excellent choice because of its zero-carbon emission and high power density among variable fuel cells. Platinum (Pt) nanoparticles are the most widely used catalyst in the hydrogen fuel cell as it has high activity and selectivity for the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR). However, the utilization of precious platinum catalyst also has many shortcomings such as Pt agglomeration, which decrease the life time of the PEMFC, and the high cost of this material. Decreasing the loading of Pt on electrodes, cathode and anode, is one of the most important challenges for this field. Catalyst support materials with high surface area, high electrical conductivity and good catalyst interaction may decrease the amount of catalyst needed and improve the catalytic efficiency. With this aim, many carbon materials such as carbon black, Vulcan XC-72, mesoporous carbon and carbon nanotubes have been investigated as a catalyst support in the hydrogen fuel cell [1, 2]. Graphene, a two-dimensional (2D) structure of honeycomb lattice material, exhibits excellent electrical conductivity (104.36 S·cm-1), large specific surface area (~2630 m2·g-1), good thermal and mechanical stability, has recently attracted great attention as a catalyst support [3]. Several publications have successfully developed Pt catalyst supported on reduced graphene oxide (rGO) to improve the PEMFCs performance. This process of synthesizing Pt-graphene based catalyst mostly starts from graphene oxide (GO) produced by Hummers method, which leads to environmental and safety issues (use KMnO4, strong oxidizing agents and concentrated H2SO4), takes a long time and costly [4]. This work presents an alternative to Hummer’s method to produce GO and rGO by the Electrochemical Exfoliation of Graphite. A simple two electrodes configuration, counter electrode in different electrolyte solutions (NH4NO3 or (NH4)2SO4) has been carried out to produce high quality exfoliated graphene oxide (EGO) in a fast, efficient and environmental friendly way, producing also high yield in comparison with the traditional Hummer’s method. Additionally, the functional groups of nitrogen and sulphur coming from the electrolyte solution are able to be introduced into EGO, which influence the local electronic structure as well as improve polarization of the graphene network [5, 6]. Therefore, this study presents an environmentally friendly and a cost-effective approach to prepare. Pt nanoparticles supported on EGO, which were synthesized by a modified polyol reduction method to compare with the traditional Pt supported on carbon black (Pt-CB) and rGO produced by Hummers’ method (Pt-GO) to improve the efficiency and the long time performance of a PEMFCs. Successful preliminary results can be observed in Fig 1, which shows that Pt-EGO can improve the electrochemical surface area (ECSA) over Pt-CB and Pt-GO. Meanwhile, Pt-EGO can influence the durability of the catalyst with chrono amperometry measurement. This study will discuss the characterisation of developed catalysts and their efficacy in a working fuel cell system.