Premixed Stagnation Flame Synthesized TiO2 Nanoparticles with Mixed Phases for Efficient Photocatalytic Hydrogen Generation

Mixed-phase TiO2 nanoparticles (10–20 nm) composed of rutile, anatase, and srilankite phases are prepared through a one-step flame synthesis method. The phase composition of TiO2 nanoparticles can be easily tuned by changing the flame conditions such as the gas flow rates of the fuel, oxygen, and argon carrier. The optimized anatase/rutile/srilankite TiO2 sample with as low as 0.1 wt % of Pt cocatalyst exhibits remarkable photocatalytic H2 generation rate of 21.9 mmol h–1 g–1 and an apparent quantum efficiency (AQE) of 39.4% at 360 nm, higher than those of anatase/rutile or anatase TiO2. The less studied srilankite phase is first time investigated for photocatalytic H2 generation. It is revealed that the relatively low content of srilankite phase in TiO2 could efficiently promote charge separation and transportation. It is remarkable that, compared to the commercial P25 TiO2, the flame-made TiO2 significantly improves Pt reduction and dispersion owing to the oxygen vacancies and surface defects. The optim...