The preserved S-scheme band structure of graphitic carbon nitride/bismuth oxobromide after the introduction of black phosphorus driven by an internal electric field: achieving significantly enhanced photocatalytic performance†
Abstract
This work presents a referential case in which the original efficient band structure of a binary composite remains intact when a third component is introduced. The spherical BiOBr (BOB) possesses good stability and a low valence band position, but its poor separation efficiency of photogenerated charge carriers limits its application. This limitation can be overcome by combining it with two-dimensional g-C3N4 nanosheets (CNs) in an appropriate proportion. The soft and lightweight texture of CNs ensures effective wrapping of BOB to form a tight integration. However, the limited visible light absorption of CNs/BOB hampers the overall catalytic effect. Black phosphorus nanosheets (BPs) exhibit outstanding light absorption over a wide range, and their incorporation into CNs/BOB can compensate for this deficiency. Additionally, new migration pathways can be formed to further enhance the spatial separation of photogenerated charge carriers. Furthermore, scavenging experiments and EPR tests confirmed that the presence of BPs did not alter the original S-scheme band structure between CNs and BOB, owing to proper band alignment and the effect of an internal electric field, allowing the useful photogenerated electrons and holes with strong redox ability to continue playing a pivotal role. As a result, 88.3% of tetracycline hydrochloride (TCH, 200 mL, 20 mg L−1) can be removed under visible light in 60 minutes using 50 mg of 6BPs/CNs/BOB1:2, with good reusability and adaptability to various pollutants. This work provides a valuable strategy for designing and preparing ternary composites with attractive photocatalytic performance driven by visible light.