Abstract
The importance of carbonaceous catalyst support materials in polymer electrolyte membrane (PEM) fuel cell is well known. In this study, we used two different types of commercial graphene nanoplatelets (GNPs) that have respectively 181 m2/g (G1) and 745 m2/g (G2) surface areas and their pyrolyzed forms with and without melamine as platinum (Pt) catalyst support. The GNPs pyrolyzed with melamine were called as M-G1, M-G2; while pyrolyzed without melamine were called as P-G1, P-G2 through the study. Solely, M-G2 sample was nitrogen (N)-doped (2.3%) via pyrolysis by means of melamine. Pt nanoparticles (NPs) were loaded on these support materials by using microwave irradiation technique. PEM fuel cell performance tests were conducted in order to determine the electrochemical activity of the Pt/GNPs catalysts along with polydimethylsiloxane (PDMS) polymer as catalyst binder. Pt/G2 and Pt/M-G2 provided the better PEM fuel cell performance results according to the Pt/G1 and Pt/M-G1 with PDMS polymer. Both of Pt/M-G1/PDMS and Pt/M-G2/PDMS composites gave the lower performance values compared to their pristine cases. Beside, conventional Nafion solution was also used as catalyst binder in the content of catalyst inks of the best two catalysts (Pt/G2, Pt/M-G2). PDMS and Nafion were compared with each other in terms of PEM fuel cell performance. Based on the results (@0.6 V), Pt/G2/PDMS (531.8 mA/cm2) prevailed the Pt/G2/Nafion (473.7 mA/cm2). However, performance sequence changed inversely for the Pt/M-G2/PDMS (62.6 mA/cm2) and Pt/M-G2/Nafion (329.9 mA/cm2). The highest current density value belongs to the Pt/G2/PDMS composite. The higher surface area (for the well distribution of Pt NPs) and the larger pore volume (for the better transfer of reactant gases) provided by the G2 are effective in its superiority. Under catalyst binder mission, the high oxygen permeability and hydrophobicity of the PDMS polymer is also thought to be beneficial for the improved PEM fuel cell performance. Consequently, Pt/G2/PDMS composite is the best candidate for being high-performance catalyst/binder couple in order to be used in the cathode catalyst layer (CL) of PEM fuel cell.
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