Substrate dependent photocatalytic performance of TiO2/MWCNT photocatalysts

• TiO2/MWCNT nanocomposite photocatalysts were prepared by facile sol–gel method.
• Phenol and oxalic acid were decomposed with the photocatalysts.
• The presence of MWCNTs definitely has significance in the photodegradation.
• MWCNT content enhanced the photoactivity notably in case of oxalic acid.

Titanium dioxide multiwall carbon nanotube (TiO2/MWCNT) composite photocatalysts were synthesized by the hydrolysis of titanium containing precursor adsorbed on the surface of MWCNT. Annealing was applied to convert amorphous titania oxide-hydroxide to crystalline material. The prepared photocatalysts were characterized with TEM, XRD and Raman spectroscopy. XRD and Raman results showed that only anatase-phase titanium dioxide is present in the samples. Generally this is the preferred phase as it is photocatalytically more active than all other TiO2 phases. TEM investigations revealed that the prepared photocatalysts have well defined structures; the MWCNTs were decorated with TiO2 nanoparticles. The photocatalysts were tested in aqueous-phase photocatalytic reactions using sol–gel prepared TiO2 as references. The choice of model compounds was based on their aromatic and polar characteristics. The concentration of the model compounds (phenol and oxalic acid) was measured by HPLC technique. These investigations showed that photocatalytic activity does depend on the model compound and the percentage of MWCNT content. The sample containing 5% MWCNT was the most efficient for oxalic acid decomposition under UV irradiation while the sample containing 1% MWCNT performed the best in phenol decomposition under our experiment conditions. For both model compounds, there are MWCNTs containing samples which are better than the similar way prepared TiO2 reference samples.

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