Evaluation of Atmospheric-Pressure Plasma for Improving Photoelectrochemical Response of Titania Photoanodes

摘要

A synergistic combination of nanostructure synthesis and surface engineering was used to enhance the photoelectrochemical activity of titanium dioxide (TiO2) photoanodes. Titania nanotubular arrays were synthesized by electrochemical anodization of Ti thin foils. An atmospheric-pressure helium plasma followed by exposure to nitrogen was used to modify the surface properties of TiO2 nanotubes. The photocurrent from plasma-treated samples was approximately 25% higher than that from untreated samples. This increase in photoactivity could be ascribed to the following: 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, although bulk electronic properties remain unchanged during plasma treatment.