Evolution of a skeleton structured TiO2 surface consisting of grain boundaries

Anodization of a polycrystalline TiO2 electrode in a sulfuric acid solution under UV light irradiation causes photoelectrochemical dissolution (photoe tching) with current efficiencies of several percent and hence leads to a u nique microfabrication of its surface. Control of the electrode potential m ade it possible to dissolve selectively the grain boundary or the grain bul k of the electrodes. Upon photoetching the electrode under weak anodic pola rization, namely, at a potential close to the photocurrent onset, a 'skelet on' structured TiO2 surface consisting of grain boundaries evolves as a res ult of a selective dissolution of the grain bulk. The micro-structural stud y of the grain boundary was carried out by transmission electron microscopy (TEM). The remaining grain boundary has a sandwich structure that consists of two thin platelets of crystalline phases of TiO2 attached each other, h aving different crystal orientations. (C) 1999 Elsevier Science S.A. All ri ghts reserved.