Preparation and photoelectrochemical properties of functional carbon nanotubes and Ti co-doped Fe2O3 thin films

Functional carbon nanotubes (CNTs) were incorporated into Ti-doped Fe₂O₃ thin films by a facile, one-step co-electrodeposition method. The films were characterized by X-ray diffraction, scanning electron microscopy, UV–visible absorption, and X-ray photoelectron spectroscopy. The introduction of CNTs results in a better absorption in visible region and greatly enhances the photoelectrochemical properties of the Ti–Fe₂O₃ films. The improved photoelectrochemical properties of the CNTs and Ti co-doped Fe₂O₃ films are due to the charge equilibration which interplays between the Ti–Fe₂O₃ and CNTs. The effect of CNTs to mediate fast charge transfer and to retard charge recombination rate in the composites is also demonstrated by kinetics analysis and electrochemical impedance spectroscopy. The influence of different groups-modified CNTs and different content of CNTs was also studied. The highest photocurrent is 4.5 mA/cm² at 1.23 V (vs. RHE) obtained by incorporating 0.10 mg/mL amino-group modified CNTs in the Ti–Fe₂O₃ film. The amino-functionalized CNTs doped film exhibits the highest photoelectric response compared with those doped by the pristine and acid-treated CNTs under the same conditions, which can be ascribed to the better hydrophilicity and dispersibility of the amino-functionalized CNTs.