Study On Preparation And Photocatalytic Properties Of Co-doped Nano-TiO₂Photocatalyst

Nano-titanium dioxide has been hailed as green environment-friendly photocatalyst,for its non-toxic, high photocatalytic activity, high stability, fast degration rate to oganicsand the green degraded products （mainly CO₂and H₂O）. However, TiO₂has its own defectsand it can response only under UV irradiation. Therefore, it should be modified in order toexpand its utilization under visible light.Titanium dioxide powers were prepared by the ultrasonic-alkoxide hydrolysis methodin low-temperature. Its structure and properties were characterized by means of XRD, BET,SEM, and FT-IR. The research results were as follows:（1）Experiments were conducted to investigate the effects of titanium source,synthesis temperature, ultrasound-assisted and others on pure nano-TiO₂prepared. The bestreaction conditions obtained when using titanium tetra-isopropoxide （TTIP） as a source oftitanium, ultrasonic for0.5h, the synthesis temperature was75℃, and reaction time was1.5h. The samples prepared under such conditions were anatase nano-TiO₂, which had gooddispersion, smooth surface, none particle aggregation, uniform particle size and smallparticle size （11nm）. Degradation of methyl orange was used to evaluate the photocatalyticactivity of the samples under UV light. The results showed that: when the catalyst dosagewas0.8g/L and the initial concentration of methyl orange was8mg/L, the degradation rateof methyl orange solution was more than95%within180min under UV light.（2）Taking cheap thiourea as a nitrogen and sulfur source to modify TiO₂withco-doped non-metallic elements N and S. The co-doped optimum experimental conditionswere that ultrasonic for0.5h, synthesis temperature was85℃, doping concentration was5%,calcining temperature was200℃. The sample prepared was anatase TiO₂and its particle diameter was about5.32nm, specific surface area was285.84m²/g, average pore size was6.65nm, pore volume was0.47cm³/g. When the calcined temperature was600℃, thecrystalline phase turned into rutile; the infrared spectroscopy indicated that the element Swas successfully doped into TiO₂, and the EDS testing results showed that the element Nand C were also doped into TiO₂.（3）Degradations of methyl orange were conducted on codoped samples to evaluatethe photocatalytic activity of samples under visible light. The results showed that: thesample calcined under200℃had the highest photocatalytic activity and the degradationrate of methyl orange was more than87%under visible light illuminated5h.（4）The samples doped and undoped were experimented to compare photocatalyticactivities under ultraviolet irradiation. It was found that the doped catalyst can greatlyincrease the degradation rate of methyl orange to100%under UV light within100min,while the undoped sample needed180min under UV light to get the same degradation result.So doping can greatly improve the photocatalytic activity of catalyst under ultraviolet light.In this paper, ultrasonic-alkoxide hydrolysis method was used to prepare Nano-TiO₂co-doped with N and S in low temperature, and the production was with high photocatalyticactivity under visible light.