BiOI/TiO₂nanotube arrays, a unique flake-tube structured p–n junction with remarkable visible-light photoelectrocatalytic performance and stability

Abstract

A series of unique flake-tube structured p-n heterojunctions of BiOI/TiO2 nanotube arrays (TNTAs) were successfully prepared by loading large amounts of BiOI nanoflakes onto both the outer and inner walls of well-separated TiO2 nanotubes using anodization followed by the sequential chemical bath deposition (S-CBD) method. The as-prepared BiOI/TNTAs samples were characterized by X-ray diffraction, electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy and nitrogen sorption. The photoelectrocatalytic (PEC) activity and stability of the BiOI/TNTAs samples toward degradation of methyl orange (MO) solutions under visible-light irradiation (λ > 420 nm) were evaluated. The visible-light PEC performance of BiOI/TNTAs samples was further confirmed by the transient photocurrent response test. The results from the current study revealed that the 5-BiOI/TNTAs sample exhibited the best PEC activity, favourable stability, and the highest photocurrent density among all the BiOI/TNTAs heterostructured samples. The combined effects of several factors may contribute to the remarkable visible-light PEC performance for the 5-BiOI/TNTAs sample including a 3D connected intertube spacing system and an open tube-mouth structure, strong visible-light absorption by BiOI, the formation of a p-n junction, larger specific surface area, and the impact of the applied external electrostatic field.

Retracted: Bi5O7I Nanobelts: Synthesis, Modification, and Photocatalytic Antifouling Activity

“…Therefore, as an electron pool, Bi 2 O 2 CO 3 promotes the separation and migration of charge carriers, and thus enhances the photocatalytic activity. BiOI is always poor in photocatalytic activity by itself; however, as a p‐type semiconductor, it can form a p‐n junction with n‐type Bi 2 O 2 CO 3 , which also furthers the separation of charge carriers. Moreover, the improved optical absorption from BiOI and the large E g of Bi 5 O 7 I guarantee enough oxidation ability and rate over MG.…”

“…Among the reported photocatalysts, bismuth‐containing materials such as Bi 2 WO 6 , BiVO 4 , Bi 2 O 2 CO 3 , and BiOX (X=Cl, Br, I) have aroused much interest because of their particular layered structures and excellent photocatalytic performances. As a result of its narrow band gap (1.7–1.83 eV), BiOI can absorb the majority of visible solar light (λ <700 nm) and is thus among the most promising photocatalytic semiconductor materials. However, many studies have illustrated that, by itself, BiOI is always poor in photocatalytic activity because of its low valence band edge potential .…”

Heterojunction Photocatalysts

“…Specifically, an effective p–n heterojunction photocatalyst can be obtained by combining p‐type and n‐type semiconductors. Before light irradiation, the electrons on the n‐type semiconductor near the p–n interface tend to diffuse into the p‐type semiconductor, leaving a positively charged species (see Figure ) . Meanwhile, the holes on the p‐type semiconductor near the p–n interface tend to diffuse into the n‐type semiconductor, leaving a negatively charged species.…”

Enhancement of photocatalytic and photoelectrochemical properties of BiOI nanosheets and silver quantum dots co‐modified TiO2 nanorod arrays

“…The HRTEM image shows two lattice fringes (Figure B). The lattice fringe spacing of 0.236 nm corresponds to the (111) crystal plane of Ag, and 0.275 nm 0.204 nm correspond to the (110) (200) crystal planes of BiOI . Therefore, XRD, XPS, and HRTEM analyses successfully confirmed the BiOI/Ag modificatory TNR structure.…”

“…In order to study the morphology and microstructure of the samples, TEM and HRTEM analyses were performed and detailed microstructure information was obtained for TBA-2. Figure 5A 31,32 Therefore, XRD, XPS, and HRTEM analyses successfully confirmed the BiOI/ Ag modificatory TNR structure.…”