Abstract
Solution combustion synthesis was used to produce a junction between different TiO2 supports (anatase TiO2 nanorods (TNR) and nanoparticles (TNP) and TiO2 with anatase core and amorphous shell (a-TNR)) and narrow bandgap (BG) semiconductor β-Bi2O3. β-Bi2O3 acted as a visible-light photosensitizer and enabled us to carry out photocatalytic oxidation of water dissolved bisphenol A (BPA) with TiO2 based catalysts under visible-light illumination. Heterojunction between TiO2 and β-Bi2O3 in TNR + Bi and TNP + Bi composites enables the transfer of visible-light generated holes from the β-Bi2O3 valence band (VB) to the upper lying TiO2 VB. A p–n junction, established upon close chemical contact between TiO2 and β-Bi2O3, enables the transfer of visible-light generated electrons in the β-Bi2O3 conduction band (CB) to the TiO2 CB. In TNR + Bi and a-TNR + Bi composites, the supplied heat energy during the synthesis of samples was not sufficient to completely transform (BiO)2CO3 into β-Bi2O3. A p–n junction between (BiO)2CO3 and β-Bi2O3 enables the transfer of electrons generated by β-Bi2O3 to (BiO)2CO3. Hindered charge carrier recombination originating from the crystallinity of TiO2 is a more important factor in the overall kinetics of BPA degradation than high specific surface area of the amorphous TiO2 and reduction/oxidation of surface adsorbed substrates.
Highlights
Industrial development and an increase in agriculture are linked with the release of a large number of pollutants into aquatic bodies that cannot be degraded by natural means [1]
TiO2 is one of the most used and investigated materials used as catalysts in the heterogeneous photocatalytic oxidation process [4,5,6,7,8,9], its use is limited by two drawbacks
SEM images of pure TiO2 (Figure 1) show that the latter is present in the ellipsoidal shape (TNP sample) on one side and in the rod-like shape (a-TiO2 nanorods (TNR) and TNR solids) on the other
Summary
Industrial development and an increase in agriculture are linked with the release of a large number of pollutants into aquatic bodies that cannot be degraded by natural means [1]. In the past, advanced oxidation processes (AOPs) have received significant interest for applications in wastewater treatment [2]. To generate OH· radicals, several processes based on different approaches have been investigated, for example, processes based on: UV, Fenton, heterogeneous photocatalysis and ozone [3]. When using heterogeneous photocatalytic processes for generating OH· radicals, there is no need to use potentially hazardous oxidants, and it can be conducted at ambient conditions. Elements of a successful heterogeneous photocatalytic system are the light source, the appropriate configuration of the reactor system and the catalyst. TiO2 is one of the most used and investigated materials used as catalysts in the heterogeneous photocatalytic oxidation process [4,5,6,7,8,9], its use is limited by two drawbacks. First is that due to its wide bandgap (BG) energy of 3.0–3.2 eV, it can only make photocatalytic active by ultraviolet light (UV)
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