M/g-C 3 N 4 (M=Ag, Au, and Pd) composite: synthesis via sunlight photodeposition and application towards the degradation of bisphenol A

Abstract

In this work, natural sunlight successfully induced the deposition of gold (Au), silver (Ag), and palladium (Pd) nanoparticles (NPs) with 17.10, 9.07, and 12.70 wt% onto the surface of graphitic carbon nitride (g-C₃N₄). The photocatalytic evaluation was carried out by adopting Bisphenol A (BPA) as a pollutant under natural sunlight irradiation. The presence of noble metals was confirmed by EDX, HRTEM, and XPS analysis. The deposition of Ag NPs (7.9 nm) resulted in the degradation rate which was 2.15-fold higher than pure g-C₃N₄ due to its relatively small particle size, contributing to superior charge separation efficiency. Au/g-C₃N₄ unveiled inferior photoactivity because the LSPR phenomenon provided two pathways for electron transfer between Au NPs and g-C₃N₄ further diminished the performance. The improved degradation lies crucially on the particle size and Schottky barrier formation at the interface of M/g-C₃N₄ (M=Au, Ag, and Pd) but not the visible light harvesting properties. The mechanism insight revealed the holes (h⁺) and superoxide radical (^• O₂⁻) radical actively involved in photocatalytic reaction for all composites.