For simplicity, we do not allow the band edges to slip at the Si/TiO2 interface (which would reduce the band bending of the TiO2 at the Si interface), although this likely occurs. Nevertheless, in such a case, the interpretation of the data regarding the equivalent circuit is not affected. As the ferrocenium ion absorbs strongly in the visible region, significant light attenuation occurred during the EIS experiments in aprotic solvent. For a direct comparison to the protic results, an experiment under 0.05 sun in 1 M H2SO4 was carried out. In all cases, a low frequency process in addition to the silicon RC element was observed. Therefore, we currently conclude that species intercalated into the a-TiO2 are not the root cause of the non-faradaic process observed in p-Si|a-TiO2|Pt devices.