Microwave heating preparation of phosphorus doped g-C_3N_4 and its enhanced performance for photocatalytic H_2 evolution in the help of Ag_3PO_4 nanoparticles

摘要

This paper synthesized a novel Ag3PO4/P-g-C3N4 via a two-step chemical route i.e. microwave-assisted heating and ion-exchange procedures. The as-synthesized hybrid presented high efficiency for photocatalytic hydrogen production. Systematic investigation indicated that phosphorus was successfully doped into the g-C3N4 framework through microwave heating the mixture of melamine and NH4H2PO4 for 40 min, which increases the BET surface area, broadens the visible light response region, and elevates the separation efficiency of electron-hole pairs. The Ag3PO4 nanoparticles were decorated on the optimal P-g-C3N4 sample via an ion-exchange process. Due to the instability of Ag3PO4, the formed composite is actually Ag/Ag3PO4/P-g-C3N4 photocatalyst. The introduced Ag3PO4 nanoparticles further improves the charge separation efficiency of P-g-C3N4, but slightly affects the surface area and optical property, which highlights the key role of the separation efficiency of electron-hole pairs in photocatalytic reaction. The best Ag3PO4/P-g-C3N4 hybrid shows a photocatalytic H-2 production rate of 1221 and 90.2 mu mol g(-1)h(-1) under simulated sunlight and visible light, respectively. This value is 2.1 and 1.4 times greater than that of g-C3N4 and P-g-C3N4, respectively. Meanwhile, the Ag3PO4/P-g-C3N4 displayed high photocatalytic stability. A probable photocatalytic mechanism of the hybrid was also suggested. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.