Fabrication of novel AgBr/Bi24O31Br10 composites with excellent photocatalytic performance

Abstract

Novel porous AgBr/Bi₂₄O₃₁Br₁₀ (AB/BOB) heterojunction composites were prepared by a hydrothermal calcination-ion exchange route and their physico-chemical properties were characterized by XRD, XPS, SEM, EDX, UV-vis DRS, BET and electrochemical measurements. The photocatalytic activity of the composites consisting of different AB/BOB mass ratios was evaluated by degradation of methylene blue (MB) under visible light irradiation. Compared with pure AB and BOB, the porous 20% AB/BOB composite exhibits much enhanced photocatalytic activity with good cycling stability. The significant enhancement in photoactivity is contributed to by both a high adsorption capacity and the separation efficiency of photo-generated electron-hole (e^--h⁺) pairs via a Z-scheme mechanism. In addition, radical scavenging experiments confirm that the reactive ·OH radicals play an important role in the photocatalytic reaction. The novel (AB/BOB) heterojunction composites could have a promising application in treatment of various dyestuff wastewaters on a large scale.

Fig. 1. XRD patterns of pure AgBr, BOB and AB/BOB nanocomposites.

Fig. 2. XPS spectra of the 20% AB/BOB nanocomposite, (a) survey, (b) C 1s, (c) Ag 3d, (d) Bi 4f, (e) Br 3d and (f) O 1s.

Fig. 3. (a)–(c) SEM images of AgBr, BOB and 20% AB/BOB, respectively. The inset in (b) shows the high-magnification SEM image of 20% AB/BOB. (d) EDX pattern of 20% AB/BOB nanocomposite.

Fig. 4. UV-vis DRS spectra (a) and (αhν)^1/2versus hν (b) of the as-prepared samples.

Fig. 5. Nitrogen adsorption–desorption isotherm of the samples (a) and the corresponding pore-size distribution of the 20% AB/BOB composite (b).

Fig. 6. Time-dependent photodegradation of MB (a) and kinetic curves of the dye degradation (b) over the as-prepared samples under visible light irradiation.

Fig. 7. (a) Cycling degradation efficiency of MB over 20% AB/BOB (reaction for 20 min). (b) XRD patterns of 20% AB/BOB before and after recycling experiment.

Fig. 8. Photocurrent responses of BOB and 20% AB/BOB composite under visible light irradiation.

Fig. 9. Effect of IPA, BQ and EDTA-2Na on the MB degradation over 20% AB/BOB composite.

Fig. 10. Schematic band diagram and possible photocatalytic process of AB/BOB composites.