Synthesis of Poly (2,2′‐(1,4‐phenylene) 5,5′‐bibenzimidazole) (para‐PBI) and Phosphoric Acid Doped Membrane for Fuel Cells

Abstract

A detailed investigation of the polymerisation conditions for poly(2,2′‐(1,4‐phenylene)5,5′‐bibenzimidazole) (para‐PBI) in polyphosphoric acid (PPA) led to the preparation of high molecular weight polymer. The polymer solutions could be used directly to produce phosphoric acid (PA)‐doped PBI membranes by the PPA process. These membranes showed very high PA doping levels, i.e., up to ∼30 moles of PA per mole of PBI repeat unit. The ionic conductivity of the membranes was 0.24 S cm–1 at 160 °C. Fuel cell performance was measured at various operating conditions by changing temperature, pressure and gases and verified the high carbon monoxide (CO) tolerance of fuel cells operating at this temperature.

Effects of geometry/dimensions of gas flow channels and operating conditions on high-temperature PEM fuel cells

“…Although the membrane must have a limit of operating temperature due to material safety, it is clear that high operating temperature allows for a higher voltage output under the same other conditions. Experimental tests conducted by Yu et al [50] reported similar results on the effect of fuel cell temperatures on the voltagecurrent performance [51] as shown in Fig. 8b.…”

“…The width of the current collection ribs is 1.0 mm. Figure 5 shows the simulated results in comparison with experimental results reported by Yu et al [50]. The results in Fig.…”

“…The present validation work takes the fuel cell properties, operating conditions, and current density from experimental work in literature [50] as input for the modeling simulation. The voltage of the fuel cell is then predicted using the model.…”

“…Yu et al [50] reported the experimental results for a high temperature PEM fuel cell with a PA-doped PBI membrane under an operation condition of 1.0 atm (absolute) and a temperature of 180°C with stoichiometric coefficients of hydrogen and oxygen of 1.2 and 2.0, respectively. They also reported experimental results which were tested using pure oxygen instead of air with the same stoichiometric coefficients of hydrogen and oxygen, respectively.…”

“…They also reported experimental results which were tested using pure oxygen instead of air with the same stoichiometric coefficients of hydrogen and oxygen, respectively. The present simulation took the fuel cell properties and parameters from the work of Yu et al [50] for simulation. The dimensions of anode flow channels are 1.0 mm in depth and 1.0 mm in width, and that for cathode channels are 1.5 mm in depth and 1.0 mm in width.…”