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 metal-free 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 more efficient and facile transfer of photogenerated charge carriers for the degradation reaction.