In this paper, we study the electrochemical properties of hydrogenated Au/TiO 2 nanowires (NWs) synthesised by seed-assisted oxidation. Hydrogenation was performed electrochemically or by annealing in forming gas. The reduction process leads to a 20× improvement in photocurrent and introduces defects at the nanowires/water interface. At high frequencies, the usual Randles circuit is used. The depletion layer defect density is estimated to be 10 16 , 10 18 and 10 20 cm −3 for “as-grown”, “Forming gas” and “electrochemically reduced” samples, respectively. At frequencies lower than the relaxation frequency, defects localised at the nanowire/water interface cause an enhancement in capacitance. Under UV irradiation, a density of 10 12 cm −2 can be estimated for these defects at about 0 V Ag/AgCl .