Simultaneous polarization engineering and selectivity regulation achieved using polymeric carbon nitride for promoting NOx photo-oxidation

Abstract

Sluggish charge kinetics and high NO2 selectivity are still the bottleneck issues that restrict the efficient NOx photo-oxidation and removal using polymeric carbon nitride (PCN). Herein, approximately 2 times higher NOx-removal performance and almost complete NO2-inhibition can be synchronously achieved by maximizing the versatility of the coupled hydroxyl groups. The experimental and computational results reveal the roles of different types of coupled-hydroxyl groups in PCN in the enhancement of photocatalytic activity in terms of NOx removal and product selectivity. The spontaneous polarization effect caused by the introduction of the structural hydroxyl into the C6N7 framework accounts for the improved separation efficiency of the carriers. The mediated role of product selectivity was attributed to the process of surface hydroxyl grafting. Different conversion pathways for NOx photo-oxidation over pristine and hydroxylated-PCN were proposed. These findings provide molecular-level insight into the multiple roles of the coupled hydroxyls and can help design efficient NOx-removal photocatalysts.