Redistribution of charge in a 2D/1D BiOBr/Bi2O2S heterojunction for the photoelectrocatalytic oxidation of organic pollutants in water

Abstract

This study presents the design of a 2D/1D BiOBr/Bi₂O₂S p–n heterojunction developed for the degradation of organic pollutants in water, addressing the issue of water contamination caused by pharmaceutical compounds. In an in situ hydrothermal synthesis method, the BiOBr nanosheets were synthesised on Bi₂O₂S nanorods in varying ratio to form a heterojunction that maximises charge separation and suppressed charge recombination. At an optimal 20% Bi₂O₂S ratio, BiOBr/Bi₂O₂S heterojunction achieved 88% degradation efficiency of ciprofloxacin and TOC removal of 60%, when compared with the pristine BiOBr and Bi₂O₂S. The wider application of the photoanode was investigated by degrading other pollutants like tetracycline and sulfamethoxazole. Comprehensive structural, optical, and electrochemical analyses confirmed the increased surface area and active sites, enhanced light properties and better charged separation. The radical trapping studies identified the hydroxyl radical as a primary contributor to the degradation process, indication the p–n heterojunction facilitated by the formation of a space charge region. This study establishes the BiOBr/Bi₂O₂S as an effective photoanode for PEC water treatment and provides a promising approach to mitigate organic pollutant detection in water.