Effects of solution pH and preparation conditions on the electrochemical behaviors of Pt(111)-Nafion interface

Abstract

The Nafion ionomer is one of the important components in the membrane electrode assemblies of proton exchange membrane fuel cells, and acts as both the proton conductor and the binder for nanocatalysts and carbon supports. To gain a better understanding of the structure-performance relationship for the membrane electrode assemblies, Pt(111)-Nafion model interfaces are fabricated, and factors affecting their electrochemical behaviors, especially the adsorption and poisoning behavior of sulfonic acid groups, have been systematically investigated using electrochemical cyclic voltammetry. Experiments show that the adsorption amount and potential of sulfonic acid groups at the interface can be influenced by solution pH and processing conditions (heat treatment, solvent type, and membrane thickness). It can be inferred that the adsorption process of sulfonate groups involves the participation of protons, and thus the number of protons, sulfonate groups and water molecules at the interface will affect the adsorption process. Additionally, our results indicate that heat treatment can regulate the poisoning effect of sulfonic acid groups at the interface, thus improving ORR activity. These findings have important implications for optimizing the preparation conditions of catalyst layers in fuel cells, improving fuel cell performance, and enhancing our understanding of the electrode-Nafion interface.