Application of Atmospheric-Pressure Plasma for Enhancing Photoelectrochemical Properties of TiO2 Electrodes

A synergistic combination of nanostructure synthesis and surface engineering was used to enhance photoelectrochemical activity of TiO₂ photoanodes. Titania (TiO₂) nanotubular arrays were synthesized by electrochemical anodization of Ti thin foils. A combination of atmospheric-pressure helium plasma and nitrogen exposure was used to modify the surface properties of TiO₂ nanotubes. The photocurrent from plasma treated samples was approximately 25% higher than untreated samples. This increase in photoactivity could be ascribed to (1) increased absorption of visible light due to bandgap reduction, (2) efficient charge separation, (3) production of optimal oxygen vacancies, and (4) increased surface area and hence enhanced electrode-electrolyte area to provide maximum optical adsorption and efficient charge transfer. The diffused reflectance ultraviolet-visible (DR-UV-Vis) absorption spectra indicated a marginal increase in absorbance for the plasma treated samples in the visible region suggesting a change in surface electronic structure even though bulk electronic properties remain unchanged during plasma treatment.