Experimental and ab initio studies of enhance photocatalytic efficiency of La-doped ZnO/g-C₃N₄ nanocomposites for bromothymol blue dye degradation

The ability of photocatalysis to clean up environmental contamination, notably in the treatment of water and air, has received extensive research. The composite materials synthesized by the coprecipitation method were made of ZnO and graphitic carbon nitride (g-C₃N₄) with various concentrations of lanthanum doping (La-ZnO). It was discovered that La metal ions were evenly distributed throughout the layered stacking structures of ZnO nanosheet, which had an impact on the band structure and increased the rate of electron-hole separation and visible light absorption. First-principles calculations show that La-doped ZnO-gC₃N₄ possesses a direct band gap and a type-II band structure with the conduction band minimum and the valence band maximum located in separate layers. A built-in electric field from the gC₃N₄ to the La-doped ZnO has been established through an analysis of charge density difference, Bader charge, work function, and band alignment. The electron-hole pair becomes spatially separated as a result, which increases the photodegradation activity. High interfacial charge transfer, efficient charge separation and migration, and high visible light optical absorbance were caused by the direct coating of ZnO on an ultra-thin g-C₃N₄ layer. The 0.6 % La-doped ZnO-gC₃N₄ degraded 97 % of the bromothymol blue (BB) dye, which was four times higher than the bulk ZnO, which could remove only about 21 % of the dye at the same time. The combined effects of lower photo corrosion, higher solar light usage owing to a hollow structure and heterostructured semiconductor photocatalysis contribute to this increased photocatalytic activity. The capacity of La-doped ZnO/g-C₃N₄ nanocomposite to effectively break down BB dye via photocatalysis suggests that it has the potential to address the problems associated with dye pollution in water systems.