Enhanced visible-light degradation of organic dyes via porous g-C₃N₄

Abstract

Graphitic carbon nitride (g-C₃N₄) was prepared by reduction of melamine by adapting a pyrolysis method. Porous g-C₃N₄ (P-g-C₃N₄) was synthesized by altering the surface as well as the morphology of g-C₃N₄ by treating with oxidizing acids (chemical protonation). The photocatalytic activity of g-C₃N₄ and P-g-C₃N₄ are estimated by degrading various organic dyes namely methyl blue (MB), crystal violet (CV), and rhodamine B (Rh-B) irradiated under sunlight. The optical absorption edge of g-C₃N₄ was found to be blue-shifted from 2.7 eV to 3 eV on protonation. The g-C₃N₄ shows superior photocatalytic degradation efficiency in comparison with pristine g-C₃N₄. The P-g-C₃N₄ shows enhanced photocatalytic degradation efficiency of 98%, 99%, and 90% for MB, CV, and Rh-B, respectively, in 180 mins under sunlight irradiation with a rate of the reaction of about 4.046 min⁻¹, 5.951 min⁻¹, and 2.260 min⁻¹. Reactive oxygen species experiments revealed that the production of^. ·OH radicals are responsible for the deterioration of dyes. The boosted degradation efficacy of P-g-C₃N₄ is attributed to an increase in the surface area thereby exposing a large number of active sites for dye degradation.

GRAPHICAL ABSTRACT

Keywords:

• Dye degradation
• sunlight irradiation
• photocatalyst
• rhodamine B
• reactive oxidation species (ROS)