Self-Phosphorylated Polybenzimidazole: An Environmentally Friendly and Economical Approach for Hydrogen/Air High-Temperature Polymer-Electrolyte Membrane Fuel Cells

The development of phosphorylated polybenzimidazoles (PBI) for high-temperature polymer-electrolyte membrane (HT-PEM) fuel cells is a challenge and can lead to a significant increase in the efficiency and long-term operability of fuel cells of this type. In this work, high molecular weight film-forming pre-polymers based on N-1,N-5-bis(3-methoxyphenyl)-1,2,4,5-benzenetetramine and [1,1 & PRIME;-biphenyl]-4,4 & PRIME;-dicarbonyl dichloride were obtained by polyamidation at room temperature for the first time. During thermal cyclization at 330-370 & DEG;C, such polyamides form N-methoxyphenyl substituted polybenzimidazoles for use as a proton-conducting membrane after doping by phosphoric acid for H-2/air HT-PEM fuel cells. During operation in a membrane electrode assembly at 160-180 & DEG;C, PBI self-phosphorylation occurs due to the substitution of methoxy-groups. As a result, proton conductivity increases sharply, reaching 100 mS/cm. At the same time, the current-voltage characteristics of the fuel cell significantly exceed the power indicators of the commercial BASF Celtec(& REG;) P1000 MEA. The achieved peak power is 680 mW/cm(2) at 180 & DEG;C. The developed approach to the creation of effective self-phosphorylating PBI membranes can significantly reduce their cost and ensure the environmental friendliness of their production.