Fig. 2

Schematic set up. a Illustrative drawing of a three-electrode system with the prepared Ti foil as the working electrodes, platinum as the counter electrode, and usually Ag/AgCl as a reference electrode, while the pH electrode as a pH meter. Reproduced from ref. [35]. b Illustrative drawing of a simple two-electrode system composed of Ti foil as anode and inert metal electrode as cathode. Anodization leads to different anodized oxide layer under different conditions. In most neutral and acidic electrolytes, a compact titania can be formed. But if dilute fluoride electrolytes are used, nanotubular/nanoporous oxide layers will be directly attached to the metal surface. Reproduced from ref. [36]