Bi4TaO8Cl/Graphene nanocomposite for photocatalytic water splitting

Sillen-Aurivillius structures like Bi₄NbO₈Cl, Bi₄TaO₈Cl, and Bi₄TaO₈Br have been expected as efficient visible light active photocatalysts thanks to their narrow band gaps less than 2.5 eV and suitable negative conduction band potential for hydrogen production reaction, 0.0 V vs NHE. However, despite their excellent potential the photocatalytic hydrogen generation efficiency of them under visible light has remained low. The low activity is usually attributed to the shallow defect levels near the conduction band, causing fast recombinations of photoexcited electrons and holes. In this study, a nanocomposite of Bi₄TaO₈Cl and graphene is proposed for overcoming this issue. The excellent electron conductivity and abundant delocalized electrons from the conjugated sp²-bonded carbon networks in graphene can facilitate the transfer of electrons from Bi₄TaO₈Cl conduction band and increase the photocatalytic efficiency. Bi₄TaO₈Cl/graphene nanocomposite was successfully prepared by a hydrothermal method, and photocatalytic activity enhanced both under UV and visible light.