Bulk-Direct Synthesis of TiO2 Nanoparticles by Plasma-Assisted Electrolysis with Enhanced Photocatalytic Performance

Abstract

A new plasma-assisted electrolysis method has been developed to synthesize amorphous TiO2 nanoparticles and exploited for the enhanced photocatalytic performance. The method is simple, environmentally friendly, produces nanoparticles directly from bulk metal, and is suitable for mass production. The process was conducted in low-concentration nitric acid electrolyte under a voltage of 450 V, the minimum necessary to produce plasma on the anode surface. The average nanoparticle size was tuned between 16 and 28 nm by controlling electrolyte concentration within the range of 5 to 15 mM. The production rate increased with time, with the maximum of 11.27 g/h. The amorphous TiO2 nanoparticles were calcined at various temperatures to determine the crystalline structures and to compare their photocatalytic effects. The structure ranged from pure anatase to rutile under various calcination temperatures; the anatase–rutile mixed phase produced at 600°C showed the highest catalytic performance, with 94% degradation of methylene blue within 30 min owing to a synergetic effect between the phases. This liquid-phase plasma-assisted electrolysis method can pave the way for large-scale synthesis of highly pure metal-based ceramic nanoparticles with narrow size distributions.