Density Functional Theory Mechanistic Insight into the Peroxidase- and Oxidase-like Activities of Nanoceria

Nanoceria have been widely applied in biosystems because of their peroxidase- and oxidase-like catalytic activities. However, the atomistic mechanisms of these activities are still open questions. Using density functional theory calculations, we propose the mechanisms for these catalytic processes. The results suggest that oxygen vacancies present in nanoceria play vital roles in the catalysis. Specifically, oxygen vacancies located in the third layer are essential to form the kinetically feasible catalytic cycles. In contrast, nanoceria without oxygen vacancies are predicted to have the weak activities because of its weak affinity for H2O2 and O-2. Instead, the O-v-free nanoceria can directly oxidize protonated TMB under an acidic condition. The intermediate formed by the one-electron reduction of O-2 during the oxidase-like catalysis is active to produce the electron paramagnetic resonance signal of O-2(center dot-). The results provide atomistic level insight into the enzyme-like catalytic activities of nanoceria, which explains the experimental findings and may help the future design of nanoceria-based enzyme mimics.