The role of exposed facets in the Fenton-like reactivity of CeO 2 nanocrystal to the Orange II

Recently, ceria-based Fenton-like reactions have been developing in wastewater treatment. Nevertheless, the effects of geometric (exposed facets) of the CeO2 on its Fenton-like reactivity have rarely been considered. In this work, shaped CeO2 nanocrystals with different exposed facets were synthesized and applied in the Fenton-like degradation of Orange II (AO7). Due to the relative low oxygen vacancy formation energy on {110} facet, H2O2 decomposition shows higher apparent activation energy with nanocubes ({100} facet) than that with nanorods ({110} and {100} facets). CeO2 nanorods calcined at 300 °C exhibits the maximal activity for the decomposition of H2O2, while that for the Fenton-like degradation of AO7 is achieved with CeO2 nanorods calcined at 500 °C. Calcination at higher temperature decreases the surface Ce(III) content of CeO2, thus lowers the H2O2 decomposition rate. On the contrary, the decrescent formation energy of oxygen vacancy, the decreased amount of surface hydroxyls, as well as reduced coordination status of surface Ce cations, play important roles in promoting the adsorption and Fenton-like degradation of AO7 for CeO2 nanorods calcined at 500 °C.