Fast charge separation and availability of surface hydroxyl groups are important aspects for photocatalysis. Fast charge separation could be achieved by forming interface between the catalysts and transition metal oxides. In the present work we accomplish charge separation by controllably forming interface between acid treated molten salt rutile TiO₂ nanorods and transition metal oxide co-catalysts. FT-IR and XPS (oxygen deconvolution) results confirmed that hydroxyl groups were enhanced on the surface of rutile TiO₂ nanorods after acid treatment. Transition metal oxide (MnO, NiO, Co₂O₃, and CuO) co-catalysts were successfully loaded on the surface of acid treated TiO₂ nanorods (ATO-NRs) by conventional wet impregnation method. HR-TEM analysis revealed fine dispersion of metal oxide nanoparticles on the surface of ATO-NRs. The photocatalytic activities of as-prepared (TO-NRs), acid treated (ATO-NRs), metal oxide loaded (MTO-NRs), and both acid treated and metal oxide loaded (MATO-NRs) nanorods were compared based on the rate kinetics and dye degradation efficiency was also determined. Cobalt oxide (1 wt%) loaded on 1.0 M acid treated TiO₂ nanorods (Co/ATO-NR), exhibited the higher photocatalytic degradation efficiency of 98.57% within 120 min compared to other photo-catalysts under solar irradiation. The synergistic effect of acid treatment and co-catalyst for improved photocatalytic activity of TO-NRs might be due to fast charge transfer of finely dispersed metal oxides on the OH rich surface of acid treated TiO₂ nanorods. Photoelectrochemical analysis demonstrated that the charge transfer process in Co/ATO-NR is significantly higher than the untreated samples. Charge transfer mechanism involved in such co-catalyst loaded photocatalyst was studied in detailed.

KEYWORDS: Synergistic effect; co-catalyst; Acid treatment; Transition metal oxides; Dye degradation

Acknowledgments

This research was supported by the BK21 plus and Basic Science Research Programs (2012R1A6A3A04038530) funded by the Korean National Research Foundation (NRF).