Photophysical and Photocatalytic Properties of BiSnSbO₆ under Visible Light Irradiation

Abstract

BiSnSbO₆ with strong photocatalytic activity was first fabricated by a high-temperature, solid-state sintering method. The resulting BiSnSbO₆ was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The results showed that BiSnSbO₆, with a pyrochlore structure and a cubic crystal system by a space group Fd3m, was well crystallized. The lattice parameter or the band gap of BiSnSbO₆ was 10.234594 Å or 2.83 eV. Compared with N-doped TiO₂, BiSnSbO₆ showed higher photocatalytic activity in the degradation of benzotriazole and rhodamine B. The apparent first-order rate constant for BiSnSbO₆ in the degradation of benzotriazole and rhodamine B was 0.0182 min^-1 and 0.0147 min^-1, respectively. On the basis of the scavenger experiment, during the photocatalytic process, the main active species were arranged in order of increasing photodegradation rate: •OH < •O₂^- < h⁺. The removal rate of benzotriazole or rhodamine B was approximately estimated to be 100% with BiSnSbO₆ as a photocatalyst after 200 min visible-light irradiation. Plentiful CO₂ produced by the experiment indicated that benzotriazole or rhodamine B was continuously mineralized during the photocatalytic process. Finally, the possible photodegradation pathways of benzotriazole and rhodamine B were deduced.

Keywords: BiSnSbO6; benzotriazole; photocatalytic degradation; rhodamine B; visible light irradiation.

Figure 1

SEM image of BiSnSbO₆.

Figure 2

The high resolution TEM picture of BiSnSbO₆ (a), the selected area electron diffraction pattern of BiSnSbO₆ (b) and the HRTEM image of BiSnSbO₆ with clear lattice fringe spacing (c).

Figure 3

(a) The Pawley refinement outcomes of XRD data for BiSnSbO₆; (b) XRD spectrum of N-doped TiO₂.

Figure 4

UV-Vis diffuse reflectance spectra of BiSnSbO₆ and N-doped TiO₂ (inset was plot of ln(αhν) versus ln(hν − E_g) or plot of (αhν)^1/2 versus hν for BiSnSbO₆).

Figure 5

The XPS spectra of BiSnSbO₆ and every element in BiSnSbO₆. The full spectrum of BiSnSbO₆ (a); Bi 4f (b); Sn 3d (c); Sb 3d and O1s (d).

Figure 5

The XPS spectra of BiSnSbO₆ and every element in BiSnSbO₆. The full spectrum of BiSnSbO₆ (a); Bi 4f (b); Sn 3d (c); Sb 3d and O1s (d).

Figure 6

(a) Degradation curves of RhB over different samples; (b) Linear relation plots of ln(C₀/C) vs. reaction time; (c) The photodegradation rate constants (k) calculated from (b); (d) Degradation curves of BZT over different samples; (e) Linear relation plots of ln(C₀/C) vs. reaction time; (f) The photodegradation rate constants (k) calculated from (e).

Figure 7

(a) Degradation curves of phenol over different samples; (b) Linear relation plots of ln(C₀/C) vs. reaction time; (c) The photodegradation rate constants (k) calculated from (b).

Figure 8

(a) Total organic carbon curves of RhB over different samples; (b) Linear plots of ln(TOC₀/TOC) vs. reaction time; (c) Total organic carbon curves of BZT over different samples; (d) Linear plots of ln(TOC₀/TOC) vs. reaction time; (e) The removal rate constants (k) of total organic carbon calculated from (b,d).

Figure 9

CO₂ generation during the RhB photodegradation (a) and the BZT photodegradation (b) over BiSnSbO₆ or N-doped TiO₂.

Figure 10

(a) The photoluminescence spectra (PL) and (b) transient photocurrent response of BiSnSbO₆ and N-doped TiO₂.

Figure 11

(a) Degradation of BZT over BiSnSbO₆ in the presence of different scavengers (1.5 mM, 2.5 vol% of reaction solution); (b) Linear relation plots of ln(C₀/C) vs. reaction time; (c) The photodegradation rate constants (k) calculated from (b).

Figure 12

Conceivable photodegradation pathway of RhB under simulated sunlight irradiation with BiSnSbO₆ as catalyst.

Figure 13

Conceivable photodegradation pathway of BZT under simulated sunlight irradiation with BiSnSbO₆ as catalyst.

Scheme 1

The photosensitization effect on RhB and BZT.

Scheme 2

The generation scheme of oxidative radicals with BiSnSbO₆ as catalyst.

Figure 14

Proposed band structures of BiSnSbO₆ and N-doped TiO₂.

Figure 15

(a) The photocatalytic efficiency of RhB degradation or BZT degradation at different recycling time with BiSnSbO₆ as catalyst.; (b) XRD spectra of BiSnSbO₆ after four recycles of RhB photodegradation or BZT photodegradation; (c) XPS spectra of BiSnSbO₆ after four recycles of RhB photodegradation or BZT photodegradation.