Fabrication of Z-scheme heterojunction of UCN/BWO for selective photocatalytic benzylamine oxidation

Abstract

Nanosheet materials have larger specific surface area and more active sites than bulk materials. In this paper, ultrathin graphite carbon nitride (UCN) nanosheets were first prepared by a multi-step calcination method, and then Bi2WO6 nanoflowers were grown in-situ on the surface of UCN by a simple hydrothermal method to synthesize ultrathin graphite carbon nitride and bismuth tungstate composite (UCN/BWO). The synthesized catalyst was applied to the photocatalytic oxidative coupling of benzylamine (BA). After reacted 5 h under light in air atmosphere, BA was almost completely converted into N-benzylidenebenzylamine, which was 3.8 times higher than that of bulk graphite carbon nitride (BCN). The enhanced photocatalytic activity was not only attributed to the thin nanosheet structure of UCN which shortened the migration distance of photogenerated electrons, but also because the construction of Z-scheme heterojunction that inhibited the recombination of photogenerated carriers and improved the oxidation ability of the catalyst. Based on density functional theory (DFT) calculation and photoelectric performance test, the existence of Z-scheme heterojunction was proved. Combined with the active species capture experiments, the pathway of electron transfer in the reaction process and the possible reaction mechanism were proposed.