Facet-Dependent Photocatalytic N₂ Fixation of Bismuth-Rich Bi₅O₇I Nanosheets

Bismuth-rich bismuth oxyhalides (Bi-O-X; X = Cl, Br, I) display high photocatalytic reduction activity due to the promoting conduction band potential. In this work, two Bi₅O₇I nanosheets with different dominant facets were synthesized using either molecular precursor hydrolysis or calcination. Crystal structure characterizations, included X-ray diffraction patterns (XRD), field emission electron microscopy and fast Fourier transformation (FFT) images, showed that hydrolysis and calcination resulted in the dominant exposure of {100} and {001} facets, respectively. Photocatalytic data revealed that Bi₅O₇I-001 had a higher activity than Bi₅O₇I-100 for N₂ fixation and dye degradation. Photoelectrochemical data revealed that Bi₅O₇I-001 had higher photoinduced carrier separation efficiency than Bi₅O₇I-100. The band structure analysis also used to explain the underlying photocatalytic mechanism based on the different conduction band position. This work presents the first report about the facet-dependent photocatalytic performance of bismuth-rich Bi-O-X photocatalysts.