Application of a new lignin/cellulose carbon xerogel/ZnO/Bi2O3/Bi° composite photocatalyst for the degradation of bisphenol-A under sunlight

This work proposed the study of a new lignin/cellulose carbon xerogel/ZnO/Bi2O3/Bi° composite photocatalyst for the degradation of bisphenol-A under sunlight. The reasoning behind the application of each component is based on the formation of multiple heterojunctions (p-n heterojunction between semiconductors, metal-semiconductor heterojunction, and carbon-semiconductor heterojunction) to hinder the recombination of photogenerated charges during the photocatalytic process. The lignin/cellulose carbon xerogel was employed as both a solid electron mediator and a reducing agent, promoting the reduction of the bismuth oxide into metallic bismuth. The results obtained from the characterization tests confirm the formation of all the intended phases in the hybrid photocatalyst. Furthermore, the inclusion of the carbon xerogel led to morphological modifications such as the formation of plate-like particles and the increase of specific surface area. The efficient formation of the heterojunctions between the composing phases of the hybrid composite led to an enhanced photocatalytic activity for the degradation of the bisphenol-A (BPA) molecule, under both simulated sunlight and visible light. The optimized composite achieved 84% degradation of the BPA under simulated sunlight and 27% under visible light irradiation, which is a great improvement in comparison to the pure ZnO, which obtained 55% degradation under simulated sunlight and 19% degradation under visible light. The enhanced photocatalytic activity of the lignin/cellulose carbon xerogel/ZnO/Bi2O3/Bi° composite was further verified by chronoamperometry tests, which evidenced its greater photocurrent generation capabilities.