Facile fabrication of novel Ag₂S/K-g-C₃N₄ composite and its enhanced performance in photocatalytic H₂ evolution

This work synthesized a novel Ag₂S/K-g-C₃N₄ photocatalyst which was effective in photocatalytic hydrogen production under simulated sunlight and visible light. Systematic investigation including TG, XRD, FT-IR, DRS, XPS, N₂-adsorption, SEM, TEM, PL, and photoelectrochemical analyses was executed to examine the structure, optical property and charge separation efficiency of the as-prepared photocatalysts. Result indicated that potassium was successfully doped into the g-C₃N₄ framework via direct heating the mixture of melamine and potassium iodide at 520 °C, which increases the BET surface area, broadens the visible light response region, and elevates the separation efficiency of electron-hole pairs. The modification of Ag₂S nanoparticles on the optimal K-g-C₃N₄ sample further improves the surface charge separation efficiency via a type-II mechanism, which was believed to be the key role in photocatalytic reaction. The best Ag₂S/K-g-C₃N₄ hybrid shows a photocatalytic H₂ generation rate of 868 and 96 μmol·g^-1·h^-1 under simulated sunlight and visible light, respectively. This value is 2.7 and 1.3 times greater than that of g-C₃N₄ and K-g-C₃N₄, respectively. Meanwhile, the Ag₂S/K-g-C₃N₄ displayed high photocatalytic stability. A probable mechanism of the synthesized photocatalyst was also suggested.