Phosphoric Acid Doped Polybenzimidazole and Sulfonated Polyether Ether Ketone Composite Membrane for Hydrogen Production in High-Temperature Copper Chloride Electrolysis

Abstract

A composite membrane of polybenzimidazole (PBI) and sulfonated polyether ether ketone (SPEEK) based electrolyzer that operates at higher working temperature above 80 °C is advantageous for faster electrochemical kinetics, higher current exchange density and more resistance to fuel impurities. A high-temperature copper chloride-based composite membrane electrolysis is proposed to overcome the issue of fuel diffusivity, membrane’s thermal and mechanical stability in hydrogen production. The phosphoric acid (PA) functionalized composite PBI and SPEEK membranes were synthesized by a standard method followed with immersion in 85 wt% phosphoric acid at different temperatures for 80 minutes. The composite membranes have been characterized for water uptake, tensile strength, thermal stability by thermogravimetric (TGA) analysis, permeability by Cu diffusion cell and ionic exchange capacity (IEC). From the result, the PA doped PBI membrane (100 °C, 80 min) shows significant improvement in tensile strength (92.23 MPa) with PA doped PBI membrane (40 °C, 80 min) exhibited the lowest Cu diffusion at 5.56 x 10−8 cm2 s−1. The composite PBI/ZrP has the advantage of the most thermally stable membrane and excellent ionic exchange capacity at 3.20 x 10−3 mol g−1.