Photocatalytic Nitrogen Oxide Removal Activity Improved Step-by-Step through Serial Multistep Cu Modifications.

Previous research has evidenced the insufficient efficiency in a one-step modified photocatalyst for NO removal. In this article, a serial multistep modification was explored to improve the NO removal activity of g-CN. In the experiment, a g-CN photocatalyst has been successfully modified by Cu elements three times on one continuous process. Meanwhile, results showed that the serial multistep modifications could improve NO removal activity by g-CN step by step. The main active species in the g-CN system were h and O but they were h and OH in the three-modified g-CN systems. Moreover, different mechanisms of activity improvement caused by the modified Cu in the serial-modified samples were identified. In the first modified sample, Cu can decompose HO molecules into OH via a Fenton-like reaction. In the second modified sample, the HO molecule is activated by Cu and decomposed into OH by the generated photoelectrons. After the third modification, the synergistic effects of the N vacancy and Cu were identified, which significantly enhanced the photocatalytic NO removal activity of g-CN. This study proposed that the serial multistep modification can be a promising method to improve the NO removal activity of g-CN stage-by-stage.