Two-dimensional/two-dimensional heterojunction-induced accelerated charge transfer for photocatalytic hydrogen evolution over Bi5O7Br/Ti3C2: Electronic directional transport

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.