Platinum on pyridine-polybenzimidazole wrapped carbon nanotube supports for high temperature proton exchange membrane fuel cells

• Higher –N: content of polymer wrapped on CNT enhances Pt loading on CNT.
• Higher –N: content of polymer wrapped on CNT enhances H3PO4 doping in catalyst layer.
• Higher –N: content of polymer wrapped on CNT enhances fuel cell performance.

We synthesize polybenzimidazole (PBI) and pyridine-modified PBIs (Py-m-PBIs) from 3,3′-diamino benzidine (DAB), isophthalic acid (IPA), and 2,6-pyridinedicarboxylic acid (PyDA). Six polymers are obtained, in which the molar ratios of [PyDA]/[IPA] are 1/0, 8/2, 6/4, 5/5, 4/6, 0/1 and the molar ratio of [DAB]/([PyPA] + [IPA]) is fixed at 1/1. These modified PBIs are used to wrap the multiwall carbon nanotubes (MWCNTs) as supports for depositing Pt nano-particles. Pt on CNTs wrapped with Py-m-PBIs (i.e., Pt-Py-m-PBI/CNTs) are used as cathode catalysts for PBI/H3PO4 based membrane electrode assemblies, on which fuel cell tests are conducted at 160 °C with non-humidified H2/O2. We show that Pt-Py-m-PBI/CNTs give better fuel cell performance than Pt/C (Pt on XC-72 carbon support) catalyst and the performance increases with the increase in the [PyDA]/[IPA] molar ratio of the Py-m-PBIs wrapped on CNTs.