Controllable synthesis of substitutional and interstitial nitrogen-doped ceria: The effects of doping sites on enhanced catalytic ozonation of organic pollutants

Nitrogen doping sites greatly affected the electronic structure of catalysts. However, identification of nitrogen doping sites in CeO2 and their effects on catalytic ozonation have never been addressed. Herein, nitrogen was selectively doped at substitutional (Ns) or interstitial sites (Ni) in CeO2 by simply controlling the heat treatment conditions. The obtained NCe2–400 with 100% Ni significantly enhanced the elimination of sulfamethoxazole to 93.7 ± 1.9% within 30 min at the initial solution pH of 6.2. The first-order rate constant reached 8.77 × 10−2 min−1, 2.1 and 4.1 times that of 50.1%Ns-doped CeO2 and ozonation, respectively. The experimental and DFT calculation results demonstrate that compared to Ns, Ni favors the formation of oxygen vacancies (OVs). Both Ni and OVs significantly decreased the energy barrier of the adsorption and activation of ozone. This study provides a simple site-tunable N-doping method and gains a new insight into the roles of Ni and Ns in catalytic ozonation.