H₃PO₄ incorporated microporous hydrogel frameworks for intermediate temperature proton exchange membrane fuel cells

Abstract

Microporous polyacrylamide/chitosan (PAAm/CS) matrix is employed as a placeholder for proton conductor H₃PO₄ benefiting from the adsorption of hydrogel material to H₃PO₄ aqueous solution. Prior to fabrication, closed microporous structure of PAAm/CS matrix is opened by a freeze drying process, following by being immersed three-dimensional PAAm/CS in concentrated H₃PO₄ aqueous solutions. Anhydrous H₃PO₄ incorporated PAAm/CS membranes are obtained after a dehydration process, which are used as intermediate-temperature proton exchange membranes (PEMs). The microporous structure, loading of H₃PO₄, proton conductivity, electrochemical behaviors, and fuel cell performances are systematically evaluated. Due to high H₃PO₄ loading in per volume unit of PEM and rapid proton migration, an impressive proton conductivity as high as 0.173 S cm⁻¹ at 165°C under anhydrous condition is recorded. A fuel cell using a thick PEM shows a peak power density of 615 mW cm⁻² with O₂ and H₂ as the oxidant and fuel respectively.

Keywords:

• Proton exchange membrane
• Fuel cell
• Hydrogel material
• Three-dimensional framework
• Proton conductivity
• Microporous structure