Removal of methyl mercaptan with highly-mobile silver on graphitic carbon-nitride (g-C3N4) photocatalyst

• Ag was easily deposited on graphitic carbon nitride (g-C3N4) by shear mixing.
• Ag ultrafine crystallites with high mobility were formed.
• Ag/g-C3N4 revealed a high adsorption capacity for methyl mercaptan.
• Ag/g-C3N4 had a high photocatalytic degradation activity under visible light.
• Morphology change of Ag in the adsorption was confirmed by TEM and XPS.

Modification of graphitic carbon nitride (g-C3N4) with silver metal significantly improved the adsorption capacity and the photocatalytic degradation activity for methyl mercaptan, which is a typical sulfurous compound, under visible light. These improvements were easily obtained by the shear mixing method. The ultrafine crystallites of metallic silver were formed on surface of carbon nitride by shear mixing of HT-g-C3N4 (Hydrothermal treated g-C3N4) in aqueous solution of silver acetate. One atom of the silver captured ca. 0.6 molecule of methyl mercaptan on average, while a silver atom deposited on TiO2 captured only 0.03 molecule. The migration of silver crystallites over the g-C3N4 surface and the formation of silver thin-layer during the adsorption of methyl mercaptan were observed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The silver crystallite on g-C3N4 seemed to have higher mobility than that on TiO2 to form the coordination suitable for the adsorption of methyl mercaptan. This coordination of Ag also enhanced the photocatalytic degradation of methyl mercaptan to dimethyl disulfide.

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