Effect of specific surface area on photoelectrochemical properties of TiO2 nanotubes, nanosheets and nanowires coated with TiC thin films

Abstract

It is recommended in the exploitation of catalyst for hydrogen generation from photoelectrochemical (PEC) water splitting to use stable, non-toxic and chemically inert electrodes. The objective in this work is to combine the merits of large surface area and absorption in ultraviolet light–visible light range of hybrid structure of titanium carbide (TiC) thin film deposited on titanium dioxide (TiO2) nanowires (NWrs), nanosheets (NShts) and nanotubes (NTbs). TiO2 NTbs were prepared by rapid breakdown anodic oxidation technique, while, TiO2 NWrs and TiO2 NShts were prepared by hydrothermal method. TiC thin film is deposited on TiO2 NWrs, TiO2 NShts and TiO2 NTbs by radio frequency (RF) magnetron sputtering. Consequently, the absorption threshold of TiO2 is moved into visible spectrum range and led to a significant improvement in the photocurrent in comparison to bare TiO2. The samples were characterized by XRD, SEM, UV/Vis and Raman spectroscopy. The chemisorption (active) surface area of the synthesized nanostructures was measured by BET technique and found to be in the order of TiO2 NTbs < TiO2 NShts < TiO2 NWrs. The influence of the specific surface area on the PEC properties of TiC/TiO2 NWrs, NSts and NTbs is investigated, and a direct proportion between surface area and photocurrent is identified. The impedance measurement has been correlated with the photocurrent-potential properties, so, the hydrogen generation efficiency. The reaction mechanism is briefly discussed.