Controlled synthesis of Bi₂O₃/BiOBr/Zn₂GeO₄ heterojunction photocatalysts with enhanced photocatalytic activity

Abstract

BiOBr/Zn2GeO4 heterojunctions decorated by Bi2O3 quantum dots (QDs; named as Bi2O3/BiOBr/Zn2GeO4 hereafter) with intriguing micro/nanostructures have been constructed via a two‐step hydrothermal route. The compositions, phases, and morphologies of Bi2O3/BiOBr/Zn2GeO4 were investigated in detail. The light absorption ability, photocurrent responses, and photocatalytic degradation of methylene blue (MB) experiments were performed to evaluate the photocatalytic activity of the micro/nanoheterostructured Bi2O3/BiOBr/Zn2GeO4, which present a degradation efficiency of 88% after 240 minutes under light irradiation (λ = 300‐600 nm) over 100 mg Bi2O3/BiOBr/Zn2GeO4 in a 100 mL, 4 mg/L MB solution. The photocatalytic performance could be retained for at least four runs, indicating its excellent reusability for the degradation of MB in aqueous solution. It is found that the photodegradation of MB over Bi2O3/BiOBr/Zn2GeO4 is mainly ascribed to a hole oxidation mechanism in combination with a superoxide oxidation process. The high photocatalytic performance of Bi2O3/BiOBr/Zn2GeO4 upon UV light irradiation can be attributed to the effective charge separation and smoothly transferring of the photogenerated charge carriers throughout the heterojunction. The feasible strategy of preparing Bi2O3/BiOBr/Zn2GeO4 ternary composites is also of benefit to fabricate other efficient heterojunction catalysts with specific morphologies and properties.

Effects of solvent‐induced morphology evolution of Zn2GeO4 on photocatalytic activities of g‐C3N4/Zn2GeO4 composites

“…For pure Zn 2 GeO 4 component, the flower-like Zn 2 GeO 4 -DETA nanosheets exhibit the highest photocatalytic performance under UV-visible light irradiation ( Figure 8A,B), which might be ascribed to its highest specific surface area, which play a significant role in elevating photocatalytic performance. 46 For g-C 3 N 4 / Zn 2 GeO 4 composites, as results were shown in Figure 8 and Figure S2, the rod-like g-C 3 N 4 /Zn 2 GeO 4 (1:1)-EG composite with more exposed (110) facets of Zn 2 GeO 4 ( Figure 4G) exhibited the most enhanced photocatalytic performance compared to pure g-C 3 N 4 . It is reported that F I G U R E 7 UV-vis absorption spectra of (A) pure Zn 2 GeO 4 samples prepared from different solvents (Inset: plots of (αhv) 2 versus energy (hv) for the band gap energies of different Zn 2 GeO 4 ; (B) The UV-vis absorption spectra of g-C 3 N 4 and g-C 3 N 4 /Zn 2 GeO 4 (1:1) composites; (C) The UV-vis absorption spectra of g-C 3 N 4 /Zn 2 GeO 4 (0.5:1)-EG, g-C 3 N 4 /Zn 2 GeO 4 (1:1)-EG and g-C 3 N 4 /Zn 2 GeO 4 (2:1)-EG in compassion to g-C 3 the density of oxygen vacancies over the (110) surface is higher than that of the (001) surface, which are very important for the production of active •OH species as the H 2 O molecules dissociate in the oxygen vacancy.…”

“…46 Figure 9A shows the photodegradation efficiencies of MB using g-C 3 N 4 /Zn 2 GeO 4 (1:1)-EG as photocatalyst under visible light irradiation by adding different scavengers, it can be observed that the photocatalytic degradation efficiency of MB decreased when the quencher of isopropyl alcohol and Lcarnosine were introduced, demonstrating the dominant role of •OH and •O 2 − species for MB degradation. To further clarify the active species dominated in the MB degradation process using g-C 3 N 4 /Zn 2 GeO 4 (1:1)-EG composite as photocatalysts, photocatalytic experiments of (0.1 mmol/L L-carnosine) and h + (6.0 mmol/L triethanolamine, TEOA) were applied to the photocatalytic system.…”

“…Specifically, the quencher of •OH (6 mM of isopropyl alcohol, IPA), •O 2 − (0.1 mmol/L L-carnosine) and h + (6.0 mmol/L triethanolamine, TEOA) were applied to the photocatalytic system. 46 Figure 9A shows the photodegradation efficiencies of MB using g-C 3 N 4 /Zn 2 GeO 4 (1:1)-EG as photocatalyst under visible light irradiation by adding different scavengers, it can be observed that the photocatalytic degradation efficiency of MB decreased when the quencher of isopropyl alcohol and Lcarnosine were introduced, demonstrating the dominant role of •OH and •O 2 − species for MB degradation.…”

Designing effective and stable S‐scheme RGO/AgVO3/AgBr hybrid with enhanced photocatalytic performance

“…14 Previous studies have proved that semiconductor photocatalyst exerts a crucial role in photocatalytic process. Recently, a number of semiconductors have been explored and tested to work as an efficient photocatalyst, such as TiO 2 , 15 Bi 2 WO 6 , 16 ZnO, 17 Zn 2 GeO 4 , 18 Cu 2 O, 19 etc. However, the applications of these traditional semiconductors in the field of photocatalysis have been greatly limited because they can only be activated under the irradiation of ultraviolet light.…”

Wide‐bandgap HfO2‐V2O5 nanowires heterostructure for visible light‐driven photocatalytic degradation

“…[38][39][40][41] Similarly, heterojunction photocatalysts have been studied due to its ability to prevent the electron-hole recombination. [42][43][44][45][46][47] V 2 O 5 was found to have improved photocatalytic activity due to the fact that the Al 2 O 3 particles trap photogenerated holes, hence enhancing the photocatalytic performances. 49 The addition of reduced graphene oxide (rGO) into V 2 O 5 has been shown to effectively separate the photogenerated charges due to the fact that the rGO serves as a trapping agent of the photogenerated electrons.…”