Interaction-determined sensitization photodegradation of dye complexes by boron nitride under visible light irradiation: experimental and theoretical studies

Abstract

In this paper, the sensitization photodegradation of single and mixed dyes by wide band gap boron nitride (BN, 3.94 eV) under visible light irradiation has been investigated for the first time. The obtained results show that the sensitization degradation of rhodamine B (RhB) most easily occurs (45.2%), followed by methylene blue (MB, 12.2%) and methyl orange (MO, 7.4%). This may occur because the photo-induced electron is the easiest to transfer from dyes to BN via hydrogen bonding (interaction between RhB and BN) and then π⋯π stacking (interaction between MB and BN). MO is an anion and BN has a negative surface, which may result in the sensitization photodegradation of MO being the worst among RhB, MB and MO. The sensitization photodegradation results of RhB–MB and RhB–MO by BN under visible light irradiation are very interesting. For the RhB–MB mixture, the photodegradation of RhB decreased to 9.2% from 45.2%, but the photodegradation of MB increased to 45.4% from 12.2%. This may occur because the MB moiety in the RhB–MB complex faces BN, and MB is less stable than RhB, leading to the increased photodegradation of MB. When RhB interacted with MO to form the RhB–MO complex, the photodegradation of RhB decreased to 2.6% from 45.2%, and the photodegradation of MO increased only to 10.7% from 7.4%. This may be due to the MO moiety in the RhB–MO complex facing BN and the transfer of the photo-induced electron from the negative MO to the negative surface of BN not being easy. This work can help facilitate a deeper understanding of the sensitization phenomena during wastewater treatment.