A simple process for synthesizing nano Pt- and/or N-doped titanium dioxide powders by microwave plasma torch

Simultaneous N- and Pt-doped TiO2 powders are usually synthesized via multi-stage processes. In this study, Pt/N-doped (sample Pt/N-TiO2), Pt-doped (sample Pt-TiO2), N-doped (sample N-TiO2), and without doping (sample TiO2) TiO2 in the form of spherical nano to micro-particles are rapidly synthesized in a single-step process by spraying clear Ti- and Pt-containing nano aerosols into an atmospheric-pressure microwave plasma torch. The anatase modified Pt/N-TiO2 powders were produced in about 0.12 s. After the collection of 14-stage impactors, the size distribution showed that the most of the particles by number were in the <10 nm stage impactor, reaching 95.21%, 96.94%, and 97.94% of the total particle numbers for N-TiO2, Pt-TiO2, and Pt/N-TiO2 powders, respectively, although the mass distribution of the powders was mainly in the 1-2.5 mu m range. Chemical composition analysis showed that the N doped contents were 0.47, 0.21, and 0.41 at.% in the N-TiO2, Pt-TiO2, and Pt/N-TiO2 powders, respectively, levels higher than that of the TiO2 sample (0.12 at.%). As a result, the photocatalytic activities of N-containing (N-TiO2 and Pt/N-TiO2 samples) powders are significantly higher than those of TiO2 and P25 under visible light degradation. The rapid production of N- and/or Pt-TiO2 powders by using a simple plasma process can thus be achieved successfully for use in photocatalytic applications. (C) 2014 Elsevier B.V. All rights reserved.