Understanding the Effect of Saturated Gases on Catalytic Performance of Graphitic Carbon Nitride (g-C₃N₄) for H₂O₂ Generation and Dye Degradation in the Presence of Ultrasound

In this article, the effect of saturated gases on H ₂O ₂ generation and dye degradation is examined using graphitic carbon nitride (g-C ₃N ₄) as a piezoelectric catalyst. A detailed catalytic evaluation is carried out using a double-bath sono-reactor, where the performance of g-C ₃N ₄ for H ₂O ₂ production and degradation of rhodamine B and indigo carmine dyes is evaluated for a range of catalyst dosage levels and saturated gases. Specific gases are selected to understand their role in the sonochemical production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) and to elucidate the catalytic mechanism. The use of an Ar–O ₂ gas mixture leads to the highest yield for H ₂O ₂ production and dye degradation due to the positive effect of argon and oxygen in the generation of H ₂O ₂ and ROS, respectively. The presence of nitrogen in both air and in an Ar–air mixture increases H ₂O ₂ generation since RNS improves the conversion of ^•OH into H ₂O ₂. In contrast, air and Ar–air negatively influences the generation of ROS, which results in a low rate of dye degradation. In this work, new insights of the mechanisms of sonochemical and piezocatalytic processes in the use of graphitic carbon nitride in catalytic applications are provided.