Tailor-Made Charged Catechol-Based Polymeric Ligands to Build Robust Fuel Cells Containing Antioxidative Nanoparticles

Abstract

Cerium oxide nanoparticles (CNPs) are investigated as radical scavengers to increase the durability of polymer electrolyte membrane fuel cells (PEMFCs). However, the practical application of CNPs in PEMFCs is hindered by the low stability of the CNPs during cell operation and the low compatibility of the CNPs with PEM. In this study, as effective antioxidants for PEMs, surface-engineered CNPs, passivated with dopamine-based copolymer ligands containing multidentate catechol pendant groups (CNP@DPLs), are reported. The DPLs provide enhanced colloidal and chemical stability in acidic and radical environments, thanks to the robust catechol binding groups and polymer backbone shielding. It is highlighted that they also improved the redox cycling ability of the CNPs, with catechol's additional radical scavenging. Using the CNP@DPLs as a model system, the effect of surface charge is also examined. Negatively charged sulfonic acid-functionalized CNPs (CNP@DSAs) exhibit the highest compatibility with PEMs. Coherently, the CNP@DSA-based reinforced composite membrane (CNP@DSA-RCM) shows the lowest disintegration rate in Fenton's test. The PEMFC based on the CNP@DSA-RCM outperforms previously reported antioxidant-based PEMFCs. Importantly, while the pristine PEMFC and Ce salt-based one undergoes degradation after 40 h, the CNP@DSA based PEMFC retains its performance even after 100 h.