Single near-infrared-laser driven Z-scheme photocatalytic H2 evolution on upconversion material@Ag3PO4@black phosphorus

Z-scheme composite is considered as a desirable photocatalyst because of its efficient separation of electron-hole pairs and enhanced redox ability. However, single near-infrared light activated Z-scheme photocatalysts have been rarely reported. In this paper, for the first time, black phosphorus (BP) decorated three-dimensional beta-NaYF4: Yb3+, Tm3+@Ag3PO4 (NYF@Ag3PO4@ BP) micro-rods are successfully synthesized. Under 980 nm laser light irradiation, NaYF4:Yb3+, Tm3+ up-conversion material transforms it to visible and ultraviolet light, which could be utilized by Ag3PO4 and BP. Due to appropriate energy level positions of Ag3PO4 and BP, a direct Z-scheme photocatalytic system could be constructed. Compared to control samples, NYF@Ag3PO4@ BP composites exhibit obviously enhanced photocatalytic activity in hydrogen evolution and their hydrogen production rates are about 10 times higher than that of pure BP. The improved photocatalytic activity is attributed to Z-scheme electron migration mechanism in composite, which is confirmed by surface redox reactions, and electron spin resonance spectra.