Phosphoric acid-doped polybenzimidazole with a leaf-like three-layer porous structure as a high-temperature proton exchange membrane for fuel cells

Abstract

Porous polybenzimidazole (PBI) membranes with a high ability to store phosphoric acid (PA) and transfer protons are promising materials as high-temperature proton exchange membranes (HT-PEMs) for fuel cell applications. However, porous PA-doped PBI membranes show poor mechanical properties due to porous structure and the PA plasticizing effect. Herein, a new leaf-like three-layer porous PA-doped PBI HT-PEM is designed and prepared, which contains an inside porous layer and two dense skin layers as the protected layers. Such a unique structure endows PA-doped PBI to reach a high PA-doping level, thus improving the proton exchange performance. The as-prepared three-layer HT-PEM exhibits the highest peak power density of 713 mW cm⁻², superior to that of a two-layer membrane (551.1 mW cm⁻²). Additionally, the durability of three-layer HT-PEM fuel cells is greatly enhanced through a cross-linking method, and only 0.064 mV h⁻¹ decay of load voltage is observed after 200 h. These results indicate that the introduction of a leaf-like three-layer porous structure is an effective strategy to design HT-PEMs with excellent performance for fuel cell applications.