In situ formation of red/black phosphorus-modified SiO2@g-C3N4 multi-heterojunction for the enhanced photocatalytic degradation of organic contaminants.

Abstract

A new heterojunction material BP/RP-g-C3N4/SiO2 was obtained by a one-step ball milling method, and its photocatalytic capacity was researched by the degradation of Rhodamine B (RhB) and ofloxacin (OFL) in simulated sunlight. The construction of an in situ BP/RP heterojunction can achieve perfect interface contact between different semiconductors and effectively promote the separation of photogenerated carriers. The composite material was well characterized, which proved that the multi-heterogeneous structure was prepared. Furthermore, the type II heterojunction was formed between the g-C3N4 and BP/RP interface, playing an important role in the degradation and promoting electron transfer. The degradation effect of BP/RP-g-C3N4/SiO2 on RhB reached 90% after 26 min of simulated solar irradiation, which was 1.8 times that of g-C3N4/SiO2. The degradation of OFL by BP/RP-g-C3N4/SiO2 reached 85.3% after illumination for 50 min, while the degradation of g-C3N4/SiO2 was only 35.4%. The mechanisms were further discussed, and ˙O2 - and h+ were found to be the main active substances to degrade RhB. The catalyst also revealed distinguished stability of catalyst and recyclability, and the degradation effect of RhB can still realize 85% after 4 runs of experiment. Thus, this study provided a novel method for the design and preparation of multi-heterojunction catalysts in the removal of organic pollutants from wastewater.