Precursor dependent - Visible light-driven g-C₃N₄ coated polyurethane foam for photocatalytic applications

Photocatalysis has emerged as a highly effective method for eliminating organic pollutants from wastewater. The immobilization of photocatalysts on a suitable solid surface is highly desired to achieve enhanced photocatalytic activity. In this work, graphitic carbon nitride (g-C₃N₄) is synthesized with three different precursors (melamine, thiourea, and urea) via a simple thermal exfoliation method and successfully immobilized on a polyurethane (PU) foam using the facile dip coating method. The photocatalytic activity of g-C₃N₄ bulk and g-C₃N₄ nanosheets-coated PU foams are compared using methyl orange dye and tetracycline hydrochloride as a test pollutant under visible light irradiation. Our results show that the type of precursors and surface area of the sample have a significant role in photocatalytic dye degradation. The urea-based g-C₃N₄ - PU foam shows better photocatalytic activity than the melamine or thiourea based g-C₃N₄ - PU foam. The scavenger test unveils that superoxide radical (O₂^●-) and holes (h⁺) are the main reactive oxidative species responsible for MO dye and TcH degradations. The cycling experiments are also carried out to confirm the reusability of the g-C₃N₄ floating catalyst for practical applications. Furthermore, a possible reaction mechanism has also been proposed.