Phosphoric acid doped polybenzimidazole membrane for high temperature PEM fuel cell

Abstract

In the present study, phosphoric acid doped polybenzimidazole (PBI) membranes with potential applications in high temperature PEM fuel cells were investigated. PBI was synthesized by polycondensation of 3,3 0 -diaminobenzidine and isophtalic acid in polyphosphoric acid. The formation of PBI was validated by H 1 -NMR and elemental analysis. PBI membranes were prepared by solution casting method and immersed in phosphoric acid in order to provide ionic conductivity. The phosphoric acid doped membranes were used to prepare membrane electrode assemblies (MEA) for PEMFC operation. Gas diffusion layer (GDL) spraying method was used to prepare the electrodes. In order to determine optimum electrode structure, the effect of electrode preparation technique on fuel cell performances was studied. Two methods were applied in which the binder differs in the catalyst ink. In the first method, 5 wt % PBI solution was used as the binder. In the second method, polyvinylidene fluoride (PVDF) was used in addition to PBI as the binder in the catalyst ink. The MEA were tested in a single cell operating at 100 C without need for humidification of reactant gases. The observed maximum power output was increased considerably from 0.015 to 0.072 W/cm 2 at 150 C when the binder of the catalyst was changed from PBI to PBI and PVDF mixture (PVDF : PBI ¼ 3 : 1). A single cell was operated up to 160 C and the power outputs of 0.032 and 0.063 W/cm 2 were obtained at operating temperatures of 125 and 160 C, respectively.

Effect of membrane electrode assembly fabrication method on the single cell performances of polybenzimidazole-based high temperature polymer electrolyte membrane fuel cells

“…Even though the effect of PTFE addition will be similar for cathodes and anodes, the influence on cell performance will mainly depend on the overpotential variation in the cathodes, since the cathodic overpotential is more dominant in hydrogen-fueled PEMFCs. 19 In Figure 2, Nyquist plots of the electrochemical impedance data are presented for MEAs with varying PTFE concentrations. In the case of F45, a sloped line is clearly observed at high frequencies, along with the typical semicircular shape at lower frequencies.…”

“…Various materials are currently being used as binders for HTPEMFCs. 18,19 Among them, polytetrafluoroethylene (PTFE) are most commonly used. [20][21][22][23][24] HTPEMFC electrodes composed of Pt/C and PTFE have the ability to transfer protons by receiving phosphoric acid from the acid-doped PBI electrolyte membrane.…”

Effect of polyvinylidene difluoride in the catalyst layer on high-temperature PEMFCs

“…However, because of its low hydrogen and oxygen permeability, hydrophilic PBI is not a suitable binder in CLs. Meanwhile, Ergun et al [20] have demonstrated that with the use of a binder containing a mixture of PBI and PVDF (PVDF/PBI ¼ 3:1), the maximum power output considerably increases as compared with that by using only PBI. Moreover, Liu et al [21] have used a mixture of PBI (5%w/w) and PVDF (1% w/w) as the binder and reported 600 h life test for an HT-PEMFC based on H 3 PO 4 -doped PBI; and Li et al [22,23] have investigated the performance of composite membranes in HT-PEMFCs.…”

Mass Transfer in the HT-PEM Fuel Cell Electrode

“…This fuel cell not only has the advantages of the conventional PEM fuel cell, but also overcomes the shortages of the conventional PEM fuel cell. Therefore, HT-PEM fuel cell is paid more and more attention [1]. Sren Juhl Andreasen et al [2] and Kaserer, Sebastian et al [3] studied respectively the effect of H 3 PO 4 and CO as a poison in HT-PEM fuel cells using polybenzimidazole (PBI) membranes.…”