Fig. 7. Sketch of tube geometry parameters and possible metal/TiO2 nanotube photocatalyst geometries obtained under different sputtering–dewetting conditions (M = metal): (a) one-cocatalyst-particle per cavity. L αUV = average UV light penetration depth in TiO2; L P = length of holes (h+) solid-state diffusion in TiO2; r HO˙ = typical diffusion lengths of generated HO˙ radicals in the liquid phase; (b) homogeneous metal decoration. W = width of the space charge layer induced in TiO2 by the Schottky junction (i.e., metal/TiO2 junction) and determined using the Mott–Schottky equation as discussed in ref. 111 and 112; and (c) top-only metal decoration and effect on the electronic properties of TiO2 nanocavities. E F = Fermi level of the metal oxide semiconductor.
