Tailoring TiO₂ Nanotubes with Iron-Based MOF precursor for Enhanced Photoelectrochemical Degradation of Methyl Red

Abstract

A metal organic framework (MOF), the MIL-88A, was used as precursor through calcination at 550°C for hematite (α-Fe2O3) which was grown on titania nanotubes (TiO2 NTs) prepared by anodization from Ti plates. The hybrid material composed of titania nanotubes and hematite (TiO2 NTs/ Fe2O3) showed a high dispersion of this iron oxide over the titania nanotubes array as it was demonstrated by FE-SEM, EDS and Raman spectroscopy characterization. Photocatalysis (PC), electrocatalysis (EC) and photoelectocatalysis (PEC) with this modified electrode were tested on 15 mgL-1 methyl red (MR) aqueous solutions dissolved in 0.5 M sulfuric acid. MR discoloration was monitored through UV-vis spectrophotometry at an analytical wavelength of 515 nm. PC experiments performed under irradiation with a 365 nm Hg lamp of a 3.5 mWcm-2 intensity did not produce any discoloration in contrast with electrocatalysis, performed under a biased voltage of ~5V supplied by a commercial photovoltaic cell, that achieved a 30% removal. PEC experiments, performed under simultaneous irradiation and biased voltage applied, reached a 66.8 % removal in contrast with pristine titania nanotubes that only achieved 50%. The material kept the catalytic activity and showed to be stable after 5 cycles under the strongly acidic conditions used.