Photodegradation of Rhodamine B and Methyl Orange over Boron-Doped g-C₃N₄ under Visible Light Irradiation

TLDR

The study proposes photodegradation mechanisms for rhodamine B and methyl orange based on comparison experiments. Graphitic carbon nitride and boron‑doped g‑C₃N₄ were synthesized by thermal condensation of melamine (with or without boron oxide), characterized by XRD, XPS, UV‑vis, and EPR to identify active species in dye photodegradation. Photodegradation of Rh B proceeds mainly by direct hole oxidation, while MO degradation is dominated by electron‑driven reduction; boron doping enhances Rh B degradation through improved adsorption and light absorption.

Abstract

Graphitic carbon nitride (g-C3N4) and boron-doped g-C3N4 were prepared by heating melamine and the mixture of melamine and boron oxide, respectively. X-ray diffraction, X-ray photoelectron spectroscopy, and UV−vis spectra were used to describe the properties of as-prepared samples. The electron paramagnetic resonance was used to detect the active species for the photodegradation reaction over g-C3N4. The photodegradation mechanisms for two typical dyes, rhodamine B (Rh B) and methyl orange (MO), are proposed based on our comparison experiments. In the g-C3N4 photocatalysis system, the photodegradation of Rh B and MO is attributed to the direct hole oxidation and overall reaction, respectively; however, for the MO photodegradation the reduction process initiated by photogenerated electrons is a major photocatalytic process compared with the oxidation process induced by photogenerated holes. Boron doping for g-C3N4 can promote photodegradation of Rh B because the boron doping improves the dye adsorption and light absorption of catalyst.