Marked Enhancement of Radical Scavenging on N-Doped CeO2 Nanocubes

Abstract

Cerium oxide (CeO₂) nanoparticles are promising radical scavengers for polymer electrolyte membrane fuel cells (PEMFCs). Metal cation doping has been extensively studied to enhance their performance, with improvements primarily attributed to increased redox-active oxygen vacancy concentration. However, heteroatom anion doping of CeO₂ remains largely unexplored. Herein, nitrogen (N)- and phosphorus (P)-doped CeO₂ nanocubes with {100} facets were synthesized and systematically evaluated using kinetic model analysis across multiple temperatures. N-doped CeO₂ exhibited radical scavenging activity 40-fold higher than pristine CeO₂ and three orders of magnitude higher than Al₂O₃ at 316 K. Kinetic modeling revealed that this enhancement arises primarily from a ~17% reduction in activation energy (from 74.6 to 62.0 kJ mol⁻¹) rather than from increased oxygen vacancy concentration. Notably, activation energy proved to be a more critical factor than oxygen vacancy concentration for CeO2 radical scavenging performance, a mechanistic insight not previously established through quantitative kinetic analysis. In contrast, P-doping showed limited enhancement due to surface passivation at high loading. These results establish activation energy tuning as an effective strategy for rational design of high-performance CeO₂-based radical scavengers for PEMFC durability and antioxidant applications.