Acid-activated carbon nitrides as photocatalysts for degrading organic pollutants under visible light

Abstract

Three-dimensional (3D) carbon nitride (C₃N₄) can be used as a promising platform for visible-light-active photocatalysts because of its suitable band positions. This study reports that HNO₃ activation improves the photocatalytic activity of 3D melamine-derived C₃N₄ (MCN) materials, which degrade the organic pollutant rhodamine B (RhB). HNO₃ treatment under reflux removes the carbonaceous impurities in MCN and introduces oxygen-containing functional groups on its surface. Under visible light irradiation, the nitric acid treated MCN (NT-MCN) completely degrades RhB within 30 min. Photophysical characterizations and control experiments with radical scavengers reveal that MCN and NT-MCN follow different reaction mechanisms. Because NT-MCN exhibits a longer photoluminescence lifetime, smaller electrochemical resistance, and larger photocurrent than those of MCN, it enables a better transfer of charge carriers during the catalytic reaction.

Keywords: C impurities; Carbon nitrides; Photocatalysis; RhB degradation; Visible light.