Solvent-free facile fabrication of gold nanoparticles loaded carbon nitride and their photocatalytic performance under visible light illumination

Abstract

A direct and simple one-step procedure was applied to prepare gold (Au) nanoparticles (NPs) embedded in graphitic carbon nitride (g-C3N4) sheets. Four samples with different Au contents (from 0.5% to 5% wt) were prepared via thermal polymerization of melamine at 550 °C in the presence of commercial Au NPs after careful mixing using a ball mill. The prepared samples were characterized by XRD, DR-UV-Vis, Raman spectroscopy, XPS, SEM and HR-TEM. Characterization data confirmed the presence of zero-valent gold nanoparticles (Au0 NPs) on the g-C3N4 lattice without any chemical changes after the synthesis. The lattice constraints were found to vary with varying Au content; however, they were very close to those of the pure g-C3N4 sample. Moreover, as the Au content increased, the band gap calculation showed no significant shift, and the band gap did not change. The photocatalytic activity of the prepared samples was investigated in the decolourization reaction of Arsenazo III dye (ArIII) dye aqueous solution under visible light illumination (420 < λ < 600 nm). The sample containing 2.5 wt% gold exhibited the best catalytic performance; the pseudo first-order rate constant of the sample was almost 2.5 times higher than that of the pure g-C3N4 sample. Moreover, the reusability study showed that Au@g-C3N4 samples were stable for up to five consecutive runs without significant changes in the photocatalytic performance.