Luciano Taveira

Enhancement and limits of the photoelectrochemical response from anodic TiO2 nanotubes

TiO2 nanotube layers were grown on titanium by a self-organized anodic oxidation. The layers consist of arrays of individual tubes with a length of ∼2μm, a diameter of ∼100nm, and a wall thickness of ∼10nm. These layers can be annealed to an anatase structure which strongly increases the photocurrent efficiency. Moreover, the nanotube layers can—under certain conditions—exhibit a drastically enhanced photocurrent compared to compact anatase layers. These strong changes in the photoresponse are attributed to the characteristics of the space charge layer within the tube wall.

Self-Organized Nanoporous Valve Metal Oxide Layers

The present work examines that formation of self-organized nanoporous oxide layers can be achieved on a whole series of valve metals directly via anodization in fluoride-containing electrolytes. In particular, nanoporous layers on IVB valve metals - Ti, Zr and Hf - are presented. The remarkable difference between the metals is the thickness, which may be essentially ascribed to the difference in chemical dissolution rates of each oxide. Morphology, structure and thickness are strongly affected by the electrolyte pH.