Low-Cost Nanomaterials for High-Performance Polymer Electrolyte Fuel Cells (PEMFCs) - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 374

Fig. 11 Molecular structures of plant hormones used in the present study. a 6-benzylamino
purine (BAP); b indole-3-butyric acid (IBA); c indole-3-acetic acid (IAA); d kinetin among
which (a) and (d) are cytokinins whereas (b) and (c) are auxins
has been investigated [ 122 ]. However, almost all of the bio-inspired strategies
discussed above, despite their fundamental interest, result in performance lower
than that of the conventional PEFCs. Nevertheless, the performance of bio-
inspired electrodes could be improved by choosing a different class of molecules
other than porphyrins, nucleobases and metalloenzymes, which take part in
physiological pathways more relevant to H 2 /O 2 fuel cells.
In this context, plant hormones constitute one of the least explored classes of
biomolecules for fuel cell applications probably due to the diversity in their
molecular structures and comparatively unknown biochemical pathways compared
to those in animal systems. Plant hormones are broadly classified as auxins, cyto-
kinins and gibberellins based on their physiological functions. Some of these plant
hormones could enhance proton transport in polymer membranes (Nafion for fuel
cell applications), due to their involvement in proton transport-related processes in
biological systems (Fig. 11 ). Accordingly, we have chosen two cytokinins, viz.
kinetin and 6-benzylaminopurine, and two auxins, viz. indole-3-acetic acid (IAA)
and indole-3-butyric acid (IBA), to test the above-said hypothesis [ 123 ].
A single cell with a geometric area of 5 cm 2 with Nafion 115 as the polymer
electrolyte membrane was tested for performance. The GDL was prepared by
brushing aslurry of Vulcan XC-72, PTFE, water and cyclohexane on a carbon
cloth until a carbon loading of 4 mg cm -2 was achieved. The GDL was heat
treated at 350 C for 30 min. Then the catalyst ink was prepared by mixing
20 wt% Pt/C, Nafion, water and isopropyl alcohol in a homogenizer for 2 min at
intervals of 20 s. The catalyst ink was then applied on the GDL by brushing so that
Pt and Nafion loading were 0.5 and 0.6 mg cm -2 respectively for both cathode as
well as anode. After applying a thin layer of Nafion over the catalyst layer for
achieving optimum Pt catalyst utilization and mass transport of reactants to the