Making Metal-Carbon Nitride Heterojunctions for Improved Photocatalytic Hydrogen Evolution with Visible Light

Gold nanoparticles were deposited on the surface of a g-C3N4 semiconductor by deposition-precipitation, photodeposition, and impregnation methods to make metal-semiconductor junctions for photocatalytic hydrogen evolution from aqueous solution containing an electron donor with visible light illumination. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV/Vis, and transmission electron microscopy (TEM). Results show that the Au/g-C3N4 prepared by the deposition-precipitation method possessed the best photocatalytic activity, due to the formation of tight Au-semiconductor heterojunctions effectively promoting the transfer of charge from light-excited g-C3N4. Surface modification of the Au/g-C3N4 with a second metal further improved the activity of the photocatalytic system, which was explained by simultaneous optimization of electron transfer by the gold and chemical reactivity by the secondary metal.