Study On The Synthetic Mechanism And Photocatalysis Properties Of Titanium Dioxide Molecular Clusters

Titanium dioxide is a wide band gap semiconductor, it can only little absorb ultraviolet of light sun, but photocatalytic activity is low. Study found that the light absorption material / Ti O2 doped system and utilizating properties of electron transfer of Ti O2 can improve the photocatalytic performance. However, the photocatalytic performance of doped Ti O2 is still not ideal and at the expense of Ti O2 photocatalytic activity cost. The use of Ti O2 transfer and transport of material photoinduced electron efficiency is affected by the microstructure greatly and high composite effect of interfacial charge leads a decrease of the photocatalytic performance.In this paper, we used tetrabutyl titanate as reactants, nitric acid as catalyst to synthesize titania clusters by the method of chemical liquid phase. The micro morphology and phase composition of molecular clusters were studied by TEM、XRD and photocatalytic properties of Ti O2 clusters was researched through photocatalytic oxidation N719 under the visible light and photocatalytic reduction of chromium six under UV light. The research draws the following conclusions:In the absence of acid solution butyl titanate only occur hydrolyze,however, in acidic solution, it can hydrolyze and polycondensate. When acidity is too high, the hydrolysis of tetrabutyl titanate was inhibited.The excess of more than Ti-O:H will occur dehydration condensation with neighboring Ti-OH, formation of cross-linked big particles; When acidity is too low,hydrolysis is more thorough and condensation is incomplete, easy to forming large irregular particles. Both are not conducive to the formation of molecular clusters. Only when the molar ratio of Ti:H+is 1:2, formating titania clusters is the most conducive. The influence onof glue solution acidity and the peptizing time are most greatiy to synthesis of Ti O2 clusters.Cluster synthesis temperature range is wide, low temperature and achieve the peptization of minimum temperature are ok. The concentration of the reactant affects synthesis of titania clusters little.The peptized product only exists(101) crystal face and does not generate other crystal face, that illustrates sol particles is small scale ordered structures, not well-developed crystal. Particle size is between the 2~ 5nm and lattice fringes is obvious, so it should be molecular clusters. The characteristics absorption band of Ti O2 clusters is 330-340 nm and UV absorption ability is about 3 times of nanocrystals.Titania clusters can be completely degrades N719, but nano crystal cannot. So,molecular cluster performance of photocatalytic oxidation of N719 is better than nanocrystalline. Peptizing time and peptizing acidityaffect photocatalytic oxidation N719 larger, peptizing temperature and reactant concentration have little effect on it. Titania clusters can photocatalytic reduction of Cr(VI) in the sunlight, but nano crystal cannot. Titanium dioxide molecules cluster light catalytic reduction of Cr(VI) only needs 10 min under ultraviolet light, nanocrystalline for 2h. Peptizing time, peptizing acidity, concentration of sol have great effect on photocatalytic reduction of Cr(VI) great. When peptisation is omplete, acidity is 0.025mol/L, the sol concentration is 1.03g/L, the photocatalytic reductioneffect is the best.