Effects of different treatment atmospheres on CeO2/g-C3N4 photocatalytic CO2 reduction: good or bad?†
Abstract
Atmospheric treatment of a photocatalyst is of great significance to the activity. In this work, oxidizing, inert and reducing atmospheres were employed to treat CeO2/g-C3N4 photocatalysts, denoted as CeCN, CeCN-N2, and CeCN-H2. Interestingly, after N2 treatment, CeCN-N2 showed the best photoreduction CO2 performance, while the poorest activity was observed on CeCN-H2. The obvious reversal of activities was explored. The H2 treatment with stronger reducibility resulted in too many defects, and then bulk defects led to the charge recombination and poor CO2 activation. On the other hand, moderately inert N2 treatment introduced both the surface oxygen defects of CeO2 and amino groups in CN heterocycles, which synergistically enhanced the photoinduced electron–hole separating efficiency and medium base sites for the CO2 activation. Furthermore, a Z-scheme photocatalytic system instead of type II (CeCN) was formed on CeCN-N2, which was provided with stronger redox, and the generated overpotential was beneficial for CO2 photoreduction.