Design and characterization of bi-functional electrocatalytic layers for application in PEM unitized regenerative fuel cells

Results concerning the development and characterization of bi-functional electrocatalytic layers for application in unitized regenerative fuel cells (URFCs) based on proton exchange membrane (PEM) technology are reported. Carbon-supported hydrophobic (10 wt.% of PTFE) Pt catalysts (40 wt.% of Pt), and Pt and Ir black powders of large specific areas have been synthesized. Their structure, morphology and electrochemical properties have been investigated using SEM, TEM, XRD analysis, and by measurements of polarization curves and cyclic voltammograms. Current–voltage curves have been recorded during water electrolysis and H2/O2 fuel cell experiments to evaluate their performances at the lab-scale (7 cm2 active area). Results show that, among various Pt–Ir compositions, the best URFC current–voltage performances are obtained with anodic electrocatalytic structures made of two adjacent porous layers, a first one made of Ir (50 wt.%) in direct contact with the polymer membrane and a second one made of Pt (50 wt.%) coated over the first one.