Activation effect of nickel phosphate co-catalysts on the photoelectrochemical water oxidation performance of TiO2 nanotubes

We present exemplary fabrications of controlled Nickel phosphate (NiPi)/TiO₂ nanotubes arrays (TNTs) in phosphate buffer for boosted photoelectrochemical (PEC) water splitting. The TNTs/NiPi composite electrodes revealed a considerably enhanced photocurrent density of 0.76 mA/cm², up to 3-time enhancements than bare TNTs, mostly because of the enhanced charge separation, decreased carrier recombination, and improving kinetics of the water oxidation. Also, we demonstrated that the NiPi can assist the PEC features of TNTs over a varied region of pH values from 1 to 14. Incorporation of NiPi over the TNTs surface advances the light absorption features of the electrode, resulting in an enhanced photogenerated charge carrier; and promotes the reactive sites for water oxidation, which was proved by the double-layer capacitance. The TNTs/NiPi photoelectrode exhibited excellent photostabilization under continuous illumination for 5 h, and the photoconversion efficiencies were 0.45%, 3-fold enhancements than with bare TNTs under the illuminations. Overall, this work might offer an innovative approach to fabricating and designing efficient electrodes with superior contact interfaces among photoanodes and numerous co-catalysts.