“…Coupling of different kinds of semiconductor photocatalysts is a promising way and can enhance photocatalytic response to visible light by increasing the charge separation and extending wavelength for photoexcitation, so that the photocatalytic efficiency for liquid and gas phase reactions was increased [8,9]. Recently, most studies have been focused on the photocatalytic properties of metal ion-doped TiO 2 , such as Fe [10], Cr [11], Co [12], Mn [13], Ag [14] and V [15] ions. The doping of metal ions, especially transition metal ions, makes it possible for TiO 2 to absorb visible light.…”