As the associated resistance represents the TiO2-catalyst interface, a Mott-Schottky plot of CTiO2 should yield the actual flat band of TiO2 under the given illumination intensity (see Figure in the Supporting Information). The Mott-Schottky plot in Figure obtained by the CTiO2 yields an n-type semiconductor with a doping density of 1.9×10 20 cm -3 , which is in good agreement with the doping density of the TiO2 layer deposited by atomic layer deposition in the literature. Based on the capacitance values and the Mott-Schottky plots, one can conclude that this R-C element represents the properties of the TiO2 layer.