Synthesis of nanocrystalline bismuth titanate photocatalysis via modified hot injection method

Abstract

Nanocrystalline bismuth titanate materials were successfully synthesized via modified hot injection method. The modified method used aqueous solution of nitric acid instead of non coordinating solvent as the reaction solvent which allowed a lower reaction temperature at 130oC. XRD and FESEM analyses showed that the synthesized material crystallized in a cubic structure with Fm3m space group with average particle size of 7.9 nm. The effect of heating temperature showed that bismuth titanate with two space groups of Fm3m and I23 were obtained after heating at 400°C for 3 hours. Interestingly, the mixed phase bismuth titanate materials have the lowest band gap energy of 2.57 eV and they showed the highest photocatalytic activity in phenol degradation UV light for 12 hours. The effect of ageing time on physico-chemical properties showed particle size of the materials increased with increasing of ageing time. As a result, bismuth titanate with 2 hours of ageing time was the best photocatalyst due to its small particle size of 6.4 nm. Similarly, surfactant content used did not affect phase formation of the materials but affected the particle size. The highest surface area of 20.2 m2/g was observed in the bismuth titanate material synthesized using oleic acid to bismuth mole ratio of 1.46:1 and it had contributed to its high photocatalytic activity of 87% phenol degradation. In order to further examine the photocatalytic activity of the nanocrystalline bismuth titanate, bismuth titanate of different bismuth to titanium mole ratios (10:1 to 18:1) were synthesized. XRD results strongly suggested the formation of solid solution as all the materials crystallized in cubic structure with Fm3m space group. Bismuth titanate with bismuth to titanium mole ratio of 10:1 has achieved the highest phenol degradation percentage of 88% due to smaller particle size as well as higher mole ratio of titanium content in the material.