Enhanced Photoelectrochemical Activity by Nickel Oxide: Laser-Based Smart Fabrication From Powders and Decoration of Titania Nanotubes

In this work, a target composed of pressed nickel powders was used for laser ablation in deionized water, as an alternative to a bulk nickel target. For the first time, a study about optimal fluence and time was conducted on a powder target. Raman spectroscopy of the resulting nanoparticles revealed characteristic peaks of nickel oxide. Highly uniform, laterally spaced titania nanotube substrates were fabricated by anodization of titanium foil and decorated by drop-casting the colloidal nanoparticle solution (a study on the drop-casted volume was conducted), followed by calcination in air. Nickel oxide decoration results in a lowering of the optical band gap. Electrochemical measurements were conducted under dark, visible, and full solar simulated light illumination. The most photoactive electrode material, which was prepared by drop-casting 200 (Formula presented.) of NiO NPs solution onto titania nanotubes, exhibited a photocurrent 9.8 times higher than that of bare titania nanotubes under visible-light illumination, significantly higher compared to previously reported results for nickel and other transition metal oxide nanoparticles used for titania nanotube decoration. Furthermore, a study on the annealing technique was conducted: rapid thermal annealing resulted in better performance than the tube furnace.