Facile synthesis of Bi2O3 nanocrystals for photocatalytic NO oxidation and its conversion pathway via in situ DRIFTS

In this work, the two different polymorphs of Bi2O3, including alpha-Bi2O3 and beta-Bi2O3, were fabricated by the post-calcined the precursor at 300 and 500 degrees C respectively. The pathway of photocatalytic NO oxidation over the asprepared photocatalyst (beta-Bi2O3) was explored. The results showed that NO removal ratio on as-synthesis samples followed the order: beta-Bi2O3(32 %) > the precursor (13 %) > alpha-Bi2O3(5 %). The ESR and in situ DRIFTS demonstrated that the superoxide (O-center dot(2)-), as the main radical, can react with the absorbed NO on the surface of alpha-Bi2O3 to generate the final products NO3- and NO2-. Therefore, such findings reveal the possible photocatalytic pathway of NO oxidation on beta-Bi2O3 based on in situ DRIFTS and give insight into understanding the polymorphism of Bi2O3 in efficient photocatalytic NO oxidation under the visible light.