An in situ annealing route to [Bi6O6(OH)2](NO3)4•2H2O/g-C3N4 heterojunction and its visible-light-driven photocatalytic performance

Known as incomplete hydrolysis products of Bi(NO3)(3)center dot 5H(2)O, basic bismuth nitrates (BBN), were commonly obtained via a solution route. Herein, BBN-CN ([Bi6O6(OH)(2)](NO3)(4)center dot 2H(2)O/g-C3N4) and Bi2O3-g-C3N4 hetero-junctions were prepared in situ by mixing g-C3N4 with baked Bi(NO3)(3)center dot 5H(2)O and subsequent calcining at 250 degrees C and 550 degrees C, respectively. The baked Bi(NO3)(3)center dot 5H(2)O as a bismuth source was crucial to the formation of highly crystalline BBN, and otherwise, the product was poor-crystalline and low photoactive. The as-prepared BBN-CN exhibited better photocatalytic activity for rhodamine B (RhB) degradation under visible light irradiation than BBN, g-C3N4, and Bi2O3-g-C3N4, although Bi2O3 is more visible-light-active. These could be attributed to higher surface areas and more negative conduction band potentials of BBN, which benefits for capturing the photo generated electrons to form active center dot O-2(-) radicals. Furthermore, the presence of g-C3N4 plays a crucial role in enlarging visible light response.