Gliding Arc Plasma Synthesis of Crystalline TiO2 Nanopowders with High Photocatalytic Activity

A warm plasma generated by gliding arc discharge, combining the advantages of both thermal and cold plasmas, is explored to synthesize TiO2 nanopowders for the first time. Air is used as the discharge gas and titanium tetraisopropoxide aerosol is carried by N-2 into the plasma. X-ray diffraction and X-ray photoelectron spectroscopy characterizations confirm that the as-synthesized nanopowders are fully crystalline TiO2. The weight fraction of anatase (f (A)) is higher than that of rutile and increases from 68.8 to 96.8 % by increasing specific energy input (SEI) from 46 to 76 kJ/mol. The effect of SEI on specific surface area (S (BET)) and BET-equivalent diameter (d (BET)) of the nanopowders is investigated. The typically spheric morphology of the particles is observed by transmission electron microscopy (TEM) and the most probable d (TEM) approaches the d (BET). All the as-synthesized nanopowders show a high photocatalytic activity comparable to that of Degussa P25.