Cobalt-Doped TiO2 Nanowire Arrays Coated with NiFe Layered-Double-Hydroxide Nanoplatelets as Photoanodes for Photoelectrochemical Water Oxidation

We demonstrate the fabrication of controlled Co-doped TiO2 nanowire arrays modified by an ultrathin NiFe layered double hydroxide (LDH) as a photoanode for enhanced photoelectrochemical water-splitting application. The Co-TiO2/NiFe LDH heterostructured photoanode exhibited a significantly enhanced photocurrent density of 1.66 mA/cm(2) at 1.23 V versus reversible hydrogen electrode, up to 1.86 times higher than that of bare TiO2, mainly because of the improved charge separation, suppressed charge recombination, and increased kinetics of the surface water oxidation reaction. The X-ray photoelectron spectroscopy measurements confirmed that TiO2 photoanodes possessed abundant oxygen vacancies, which could effectively boost the hole trapping/transfer and supply more active sites for water oxidation. Photoinduced electrochemical impedance spectroscopy indicated that enhanced conductivity could also promote photogenerated electron transfer from the thin film to the substrate. The Co-TiO2/NiFe LDH photoelectrode presented excellent photostability under 7 h of continuous illumination and an increased photoconversion of 0.55%, 2.64 times higher than that of a bare TiO2 photoelectrode.