Combined experimental and molecular simulation study of arginine/PBI composite membranes for high-temperature fuel cells

High-temperature proton exchange membranes (HTPEMs) based on arginine-modified phosphoric acid-doped polybenzimidazole (Arginine-PBI-PA) and poly(tetrafluoroethylene) phosphoric acid-doped polybenzimidazole (PTFE-Arginine-PBI-PA) were fabricated and characterized for fuel cell applications. Arginine as filler was used to prepare HTPEMs for the first time, and the Arginine-PBI-PA membrane exhibited an excellent proton conducting ability with 24.1 mS cm −1 at 160 °C while maintaining mechanical strength. Furthermore, Arginine-PBI-PA composite membrane was also appropriate for membrane electrode assemblies (MEAs), and it exhibited better fuel cell performances (0.68 V@400 mA cm −2 ) compared with the PBI-PA membranes prepared. Molecular dynamics (MD) simulation revealed that the better electrochemical properties of Arginine-PBI-PA membranes over PBI-PA membranes were ascribed to the strong interactions between the basic sites and carboxyl groups of arginine and PA molecules, respectively. In addition, the higher proton conductivity for Arginine-PBI-PA membranes was attributed to the formation of a tighter H-bonding network and the interaction between arginine non-protonated oxygen (O) and PA protons (HPA). Graphical Abstract Experimental investigation and molecular dynamics simulation of novel arginine/PBI composite membranes for high temperature PEM fuel cells