Effects of hydrothermal temperature and time on the structural and morphology of TiO2 nanotubes and functionalization with sulfonic acid

Abstract

The TiO2 nanotubes are believed to be useful in various types of applications such as catalyst support for fuel cells and act as a photocatalyst for degradation of organic contaminant in wastewater. There are several ways to synthesize TiO2 nanotubes however, the convenient way is by using the hydrothermal method. Modification of the TiO2 nanotubes is predicted to enhance the properties of the nanotubes. In this work, the effect of different hydrothermal temperatures and times on the structural and morphology of TiO2 nanotubes were observed. Besides, the TiO2 nanotubes were further functionalized with sulfonic acid and their structure and morphology were also observed. The TiO2 nanotubes were first synthesized by mixing the TiO2 nanoparticles with sodium hydroxide and placed in a Teflon-lined stainless steel autoclave with the desired temperature and duration. The suspension was then washed with hydrochloric acid and distilled water and then subsequently centrifuged to obtain a solid. The solid was dried and annealed at high temperatures to remove any impurities present in the sample. The samples were then subjected to analysis using FESEM equipped with EDX. Functionalization of the TiO2 nanotubes was done by two steps which are coupling reactions followed by in situ oxidation. FESEM images proved that the sample with hydrothermal temperature and time of 200°C and 48 hours had successfully transformed into nanotubes. EDX analysis shows that the elements present in all the samples were mainly titanium, carbon, oxygen and sodium. Besides, the FTIR analysis shows that the peak of sulfonic acid was seen at the FTIR spectra. This proves that the functionalization of TiO2 nanotubes with sulfonic acid was successfully done.