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 CeO 2 and their effects on catalytic ozonation have never been addressed. Herein, nitrogen was selectively doped at substitutional (N s ) or interstitial sites (N i ) in CeO 2 by simply controlling the heat treatment conditions. The obtained NCe2–400 with 100% N i 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%N s -doped CeO 2 and ozonation, respectively. The experimental and DFT calculation results demonstrate that compared to N s , N i favors the formation of oxygen vacancies (OVs). Both N i 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 N i and N s in catalytic ozonation.