Efficient Organic Dyes Photodegradation Catalyzed by Nickel-Species Loaded Graphitic Carbon Nitride

Bismuth-doped g-C3N4/ZIF-8 heterojunction photocatalysts with enhanced photocatalytic performance under visible light illumination

In this work, g-C₃N₄/ZIF-8 heterojunction photocatalysts were synthesised by the process by which the metal-organic framework ZIF-8 nanoparticles were grown onto the g-C₃N₄ layer in situ. Bismuth element was doped into the as-prepared g-C₃N₄/ZIF-8 material and a new type of Bi@g-C₃N₄/ZIF-8 composite photocatalysts was manufactured, in which the doping element acts in adjusting the bandgap in the photocatalysts. The prepared photocatalysts were characterised by XRD, FESEM, TEM, FTIR, XPS, UV-VIS DRS, photoluminescence and photo-electrochemical experiments. The results show that the ZIF-8 nanoparticles grown in situ were well-formed onto the g-C₃N₄ layer, and bismuth was evenly doped into the gaps of the g-C₃N₄/ZIF-8 framework. The degradation rate of methylene blue by CNZ-1.5(Bi)-12, which was a photocatalyst composed of 12% Bi-doped with g-C₃N₄/ZIF-8 material (the mass ratio of g-C₃N₄: ZIF-8 = 1:1.5), reached 86.6% under visible light irradiation within 60 min. The free radical scavenging experiment and electron spin resonance spectroscopy showed that ∙OH was the main active substance. Bismuth doping into the photocatalytic system promotes the excitation of electrons from the valence band to the conduction band and provides a good channel for the transmission of photogenerated carriers as well. It is achieved that intensive visible light absorption, the enhanced separation efficiency of photogenerated carriers, and excellent thermal stability and high recyclability in the novel composite photocatalyst, owing to the synergistic effect of the introduced bismuth with the heterostructure of g-C₃N₄/ZIF-8. Therefore, the synthesised Bi@g-C₃N₄/ZIF-8 heterojunction photocatalysts may be used as a good photocatalyst for purifying and degrading organic matter in sewage.