Surfactant effect on phase-controlled synthesis and photocatalyst property of TiO2 nanoparticles

The influence of surfactant type on phase-controlled synthesis of titanium dioxide (TiO2) was investigated by varying pH, temperature and method. Typical anionic, cationic and nonionic surfactants (SDS, CTAB and TritonX-100) with the two methods of hydrothermal and emulsion preparation were selected. The phase composition and size of synthesized TiO2 nanoparticles were characterized by XRD and FE-SEM, respectively. The photocatalytic activity of synthesized TiO2 was investigated by methylene blue (MB) degradation. Moreover, BET was used to measure the specific surface area for more understanding of the photocatalytic performance using synthesized TiO2 catalyst. Results indicated the stability, size, and shape of surfactant micelles were the main factors to determine TiO2 phase. Anatase phase was found when the micelle was small and stable. On the other hand, rutile phase occurred when the micelle lost stability and expanded in size, leading to more TiO2 aggregation around micelle. The pure anatase and pure active site rutile (1, 1, 1) TiO2 with smaller nanoparticles exhibited more effective MB photo degradation overall, although mixed phase samples showed higher degradation per unit BET area. The greater the anatase phase formed in the mixed phase TiO2, the greater the MB degradation. The highest degradation of the mixed phase was at the optimum ratio of two phases according to the synergistic effect. From this study, photocatalytic activity was affected by all factors so that one needed to consider simultaneously phase, synergistic effect of mixed phase and particle size. No one factor was deemed the most effective. (C) 2018 Elsevier B.V. All rights reserved.