Regulation Of Amino Acids On The Exposed Facet,Morphology And Crystal Phase Of TiO₂

The exposure of different crystal faces of TiO2 plays an important role in its photocatalytic activity.Studies have shown that {001},{010} and other crystal planes have high activity.Its exposure has an important influence on the improvement of photocatalytic activity.Generally,F-,SO42-,etc.can be used to adjust the crystal face exposure,but the exposure ratio of the TiO2 crystal face is not well controlled during the preparation process,and thus precise adjustment of the active crystal face is difficult to achieve.At the same time,the traditional preparation method usually uses toxic and expensive inorganic ion reagents and organic solvents as regulators.Therefore,in recent years,green non-toxic biomolecules have been used as a regulator to control the crystal plane of TiO2.As a constituent unit of a protein,an amino acid contains a polyfunctional group such as-COO-,-NH2,-SH,etc.,and these functional groups can selectively bind to different crystal faces,thereby affecting the crystal face exposure.At the same time,amino acids have been shown to be very effective in regulating the exposure of TiO2 crystal faces in a mild environment.In this paper,glutamine(a cheap and readily available amino acid widely used as a raw material,having a carboxyl group,an amino group,an acyl functional group)as a regulator was used to synthesize a hexagonal multi-walled tubular hierarchical structure with a total of {010} and {101} crystal planes,and spherical TiO2 of rutile/anatase mixed crystal phase in different solvent systems by solvothermal method.The effects of amino acid on the exposure ratio,morphology and crystal phase of TiO2 active crystal plane were studied.The main contents are as follows:1.The anatase TiO2 with hexagonal multi-walled tubular hierarchical structure with co-exposure of {010} and {101} crystal faces was synthesized by solvothermal method using titanium oxysulfate as titanium precursor,ethanol as solvent and amino acid as capping agent.By changing the type and proportion of the capping agent,the optimal parameters for the preparation of the crystal face synergistic exposure hierarchical structure were found.At the same time,changing the proportion of amino acid addition can change the morphology of the material.The results show that when the ratio of glutamine to Ti was 4:1,the obtained hexagonal multi-walled tubular TiO2 with {101} and {001} crystal faces has the strongest photocatalytic ability.The photocatalytic degradation rate of methyl orange reached 94.6%within 80 min,which was 9.37 times that of the non-added capping agent.2.A series of TiO2 materials with different crystal phase composition and morphology were synthesized by one-step solvothermal method with glutamine as the regulator.The effects of crystal phase composition and morphology on the photocatalytic activity were studied by characterization.The effect of amino acid functional groups on the phase composition of TiO2 anatase/rutile was investigated.The results showing that when the proportion of glutamine added is 0.5%,mixed TiO2 with rutile and anatase content ratio of 5:95 is obtained.The photocatalytic degradation rate of base orange reached 95.6%,which was 1.87 times that of pure rutile phase sea urchin TiO2.That because the mixed crystal TiO2 has a mixed crystal effect,and the rutile has a relatively low band gap and a high photocatalytic activity compared with anatase phase,thereby imparting excellent photocatalytic activity.