Polypyrrole for Mitigating Platinum Catalyst Poisoning in Phosphoric Acid

As a green energy technology, high-temperature proton exchange membrane fuel cells have attracted significant attention due to their simplified water-heat management and improved impurity tolerance. The core of PEMFCs is phosphoric acid-doped polybenzimidazole membranes. Nevertheless, the occupation of active sites on noble-metal catalysts by phosphoric acid molecules results in an increased consumption of noble metals. In this work, a Pt/C/polypyrrole cathode catalyst is prepared by chemical reduction, doping polypyrrole into carbon black, and then loading platinum nanoparticles, with its mass activity and specific activity exceeding those of commercial Pt/C by approximately 67 and 93%, respectively. Density functional theory calculations indicate that the adsorption energies of H3PO4 and H2PO4– on the polypyrrole surface are about 2.7 and 1.4 times stronger, respectively, while the adsorption energies with H2PO4– and PO43– were weaker than those on the Pt (111) surface. Along with the lack of a P 2p signal at 133.5 eV, it is demonstrated that the resistance of platinum to phosphoric acid poisoning results from an electronic modulation. This outcome helps address the long-standing issue of phosphoric acid poisoning of noble-metal catalysts in high-temperature proton exchange membrane fuel cells.