Polymer fuel cell components modified by graphene: Electrodes, electrolytes and bipolar plates

In this review paper we summarize recent research trends for polymer fuel cells (PEMFCs) that utilize various graphene materials described in articles published since 2007. We propose to analyze the influence of graphene in PEMFCs in three aspects: (i) as an electrode (anode or cathode), (ii) as an additive to polymer electrolyte and (iii) as a filler to bipolar plates along with some discussions on future research directions. In Section 2 of this review, we shortly present the fundamental processes of fuel cells along with important parameters such as hydrogen oxidation and oxygen reduction reactions, polarization losses, exchange current density, open circuit voltage and efficiency for fuel cells. Additionally, with curt description of various kinds of fuel cells and types of polymers applied in PEMFCs. Moreover, we discuss briefly different synthetic routes of graphene and describe selected graphene properties (Section 3). In Section 4, we analyze in detail the possibilities of applied graphene or its derivatives in various places in PEMFCs. Graphene applied to PEMFCs has a significant contribution on the increased electrical or ionic conductivity, better mechanical durability and corrosion resistance, and higher electrochemical surface area, depending on the fuel cell component that is modified. For instance, taking into consideration the function of graphene in polymer fuel cells and based on the current review, the highest value of maximum power density of 0.742 W cm−2 was found for PEMFC with graphene utilized as an anode support. The promising results open the way for the usage of graphene as a prospective material for application in fuel cells. However, the main difficulty of graphene application is the fact that this material has to be sufficiently separated by additional compounds to prevent restacking of graphene sheets.