Two-dimensional/two-dimensional heterojunction-induced accelerated charge transfer for photocatalytic hydrogen...

Regulating electron density at the active site by electronic directional transport from special channels is an effective strategy to accelerate the reaction rate in photocatalytic water splitting. Here, a novel two dimensional/two dimensional (2D/2D) Bi₅O₇Br/Ti₃C₂ heterojunction with special interfacial charge transfer channel was fabricated successfully via in-situ growth of Bi₅O₇Br on the surface of ultrathin Ti₃C₂ by using a convenient hydrolysis method. The electrostatic attraction between Bi³⁺ cations and electronegative Ti₃C₂ ensures the construction of 2D/2D heterojunction and a strong intimate interface contact between Ti₃C₂ and Bi₅O₇Br, which establishes an electronic transport channel, and shortens the charge transport distance, assuring excellent bulk-to-surface and interfacial charge transfer abilities. Meanwhile, X-ray photoemission spectroscopy (XPS) and density functional theory (DFT) calculation revealed that the local electron density at the Ti₃C₂ active sites is remarkably increased because of the transfer of interfacial electrons from Bi₅O₇Br to Ti₃C₂, which is a key factor for enhancing the photocatalytic performance. Thus, the resultant Bi₅O₇Br/Ti₃C₂ exhibits significant improvement on the performance of photocatalytic hydrogen evolution under visible light irradiation. The hydrogen evolution reaction rate obtained on the optimized Bi₅O₇Br/Ti₃C₂ composite is 1.97 times higher than that of pristine Bi₅O₇Br. This work provides a new protocol for the construction of 2D/2D heterojunction photocatalytic systems and regulating electron density by electronic directional transporting.