Benzoic acid as additive: A route to inhibit the formation of cracks in catalyst layer of proton exchange membrane fuel cells

Abstract

Cracks are a common defect in the catalyst layers (CLs) of proton exchange membrane fuel cells (PEMFCs), deteriorating their performance. This study proposes benzoic acid as a cracking inhibitor in the catalyst ink. The additive strengthens the network of catalyst particles by promoting attractive interaction within them. Molecular dynamics simulations demonstrate that the inhibitor facilitates the desorption of ionomer from the Pt/carbon surface, weakening the repulsion force within catalyst particles. Rheology experiments indicate that the addition of benzoic acid transforms the catalyst ink from a sol-like to a gel-like, improving its viscosity and storage modulus. The stronger attractive interactions within the inhibitor-added ink impart anti-cracking ability, preventing stress release during the drying process. Furthermore, optical microscopy reveals a significant decrease in both the crack area and the maximum length of cracks in the CL after incorporating the inhibitor. Specifically, the crack area decreases from 13% to 2%, while the maximum crack length decreases from nearly 400 μm to 150 μm. Single cell tests show that the inhibitor-added sample exhibits a higher peak power density of 0.893 W/cm² compared to the standard sample's 0.873 W/cm². Overall, this study presents an effective method for manufacturing high-quality CLs in PEMFCs, ensuring improved performance.