Improving built-in electric fields for effective photocatalytic activity in the rationally designed electron transfer pathway of TiO2@MoS2/Bi2S3

Abstract

The efficiency of photocatalytic activity relies on rationally controlling the rapid charge transfer channel and the interfacial electric field. In this article, a ternary TiO₂@MoS₂/Bi₂S₃ is proposed, in which TiO₂ hierarchical microspheres are assembled with MoS₂ nanosheets and Bi₂S₃ NPs. This assembly generates a substantial surface electrostatic potential difference at the interface, thereby strengthening the built-in electric field. The interfacial potential difference intensity of TiO₂@MoS₂/Bi₂S₃ is 5.6 and 1.8 times greater than that detected in TiO₂ and TiO₂@MoS₂, respectively. This considerable increase in the internal electric field significantly speeds up the migration of out-of-plane electrons at the TiO₂/MoS₂ and MoS₂/Bi₂S₃ interfaces. Driven by this enhanced field, TiO₂@MoS₂/Bi₂S₃ exhibits dramatically improved photocatalytic activity under visible light irradiation that is 8.3 times and 2.7 times higher than that of pristine TiO₂ and TiO₂@MoS₂ on the degradation rate of tetrachlorophenol (4-CP), respectively, along with 6% of incident photon-to-electron conversion efficiency (IPCE). In addition, a mechanism investigation demonstrated that the Schottky barrier is established due to the Fermi level equilibrium and the bending of the energy band, effectively inhibiting the electron backflow. Furthermore, DFT calculations and mechanism investigation revealed that the photo-induced electron transfer route in the direction of MoS₂ efficiently suppressed the electron–hole recombination process, ultimately facilitating the generation of reactive oxygen species (ROS). This work provides a comprehensive understanding of the mechanism for enhancing the built-in electric field via the formation of a dual heterostructure, constituting a promising strategy to design photocatalysts for realizing high-efficiency photocatalytic activity.