A novel strategy to construct a visible-light-driven Z-scheme (ZnAl-LDH with active phase/g-C3N4) heterojunction catalyst via polydopamine bridge (a similar "bridge" structure)

A novel strategy to construct a visible-light-driven Z-scheme heterojunction catalyst was employed by crosslinking ZnAl-layered double hydroxide (ZnAl-LDH) nanosheets with the active phase on carbon nitride (g-C 3 N 4 ) substrates via a polydopamine bridge (a similar "bridge" structure). In this paper, multiple optical and electrochemical detection methods indicated that the 0.5P-LDH_500CN photocatalyst demonstrated excellent visible-light absorption properties, photo-generated electron-hole separation ability and photocatalytic activity for p-nitrophenol under visible-light (> 420 nm), etc. A Z-scheme charge transfer mechanism via PDA bridge was proposed to achieve heterojunction charge separation. This mechanism involved the recombination of photo-induced electrons directly on the ZnAl-LDH_500 valence band through the PDA channel and the holes were captured at the conduction band energy level of the g-C 3 N 4 . The detection of active species, including O 2 -, h + and OH, further proofed the Z-scheme charge transfer mechanism, which could be speculated that all active species affected the photocatalytic reaction with the order of h + > OH > O 2 -. Meanwhile, this work also exposed that the formation of active phase in ZnAl-LDH could synergize with PDA to promote the application of visible-light-active photocatalysts based on g-C 3 N 4 materials in high-efficiency energy.