Furthermore, no change in the capacitance associated with a-TiO2 was observed in the aprotic tests involving different supporting electrolytes (Figure ). That is, introduction of an intercalating species did not change the magnitude of the non-faradaic capacitance. This indicates that the process of intercalation during the photoelectrochemical reduction is not the origin of the additional process in a-TiO2 protected photocathodes during the HER.