Cerium oxide catalyzed disproportionation of hydrogen per-oxide: a closer look at the reaction intermediate

Cerium oxide nanoparticles (CNPs) have recently gained increasing interest as redox enzyme-mimetics to scavenge the intracellular excess of reactive oxygen species, including hydrogen peroxide (H2O2). Despite the extensive exploration of CNP scavenging activity, there remains a notable knowledge gap regarding the fundamental mechanism underlying the CNP catalyzed disproportionation of H2O2. In this Letter, we present evidence demonstrating that H2O2 ad-sorption at CNP surface triggers the formation of stable intermediates known as cerium-peroxo complexes (Ce-O22-). The cerium-peroxo complexes can be resolved by Raman scatter-ing and UV-Visible spectroscopy. We further demonstrate that the catalytic reactivity of CNPs in the H2O2 disproportionation reaction increases with the Ce(III) fraction. The developed ap-proach using UV-Visible spectroscopy for the characterization of Ce-O22- complexes can poten-tially serve as a foundation for determining the catalytic reactivity of CNPs in the dispropor-tionation of H2O2.