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Porous crystalline Ni-doped TiO₂ films were produced using DC plasma electrolytic oxidation in refrigerated H₂SO₄ aqueous solutions containing NiSO₄. The crystalline phase structure consisted of a mixture of anatase and rutile, ranging from ~30 to ~80 wt % rutile. The oxide films obtained at low NiSO₄ concentration showed the highest photocurrent values under monochromatic irradiation in the UV-vis range, outperforming pure TiO₂. By increasing NiSO₄ concentration above a threshold value, the photoelectrochemical activity of the films decreased below that of undoped TiO₂. Similar results were obtained using cyclic voltammetry upon polychromatic UV-vis irradiation. Glow discharge optical emission spectrometry (GD-OES) analysis evidenced a sulfur signal peaking at the TiO₂/Ti interface. XPS spectra revealed that oxidized Ni²⁺, S⁴⁺ and S⁶⁺ ions were included in the oxide films. In agreement with photocurrent measurements, photoluminescence (PL) spectra confirmed that less intense PL emission, i.e., a lower electron-hole recombination rate, was observed for Ni-doped samples, though overdoping was detrimental.