Evaluation of Ni⁰, NiO, and NiS as a Cocatalyst Modifier on TiO₂ Nanotubes Matrix for the Enhancement of Photoelectrocatalytic Oxidation of Penicillin G

Abstract

The development of an effective cocatalyst for the modification of TiO 2 arrays has become highly desirable for the improvement of their photoelectrocatalytic properties. We investigated the modification of TiO 2 with nickel-based cocatalysts (nickel (Ni 0 ), nickel oxide (NiO), and nickel sulphide (NiS)) by electrochemical deposition. The formation of n-p heterojunctions for the Ti/TiO 2 /NiO and Ti/TiO 2 /NiS and the generation of Schottky-type barrier for the Ti/TiO 2 /Ni 0 led to the enhancement of visible light absorption and the reduction of the band gap energy, contributing significantly to improving the electrogeneration of the electron−hole and lifetime of the holes. The Ti/TiO 2 /NiS photocurrent was found to be almost two times higher than that of the Ti/TiO 2 (5.39 mA.cm −2 at +1.50 V); this result was attributed to the excellent distribution of the cocatalyst around the TiO 2 nanotube walls, which helped enhance the chemical interaction on the TiO 2 /NiS interface. Under optimized conditions (+0.50 V and UV-vis irradiation), the application of the Ti/TiO 2 /NiS electrode for the photoelectrocatalytic treatment of penicillin-G-(PG) (10 mg l −1 ) resulted in complete removal and mineralization after 60 min at pH 7. The results showed that one can potentially increase the photoelectrocatalytic efficiency of Ti/TiO 2 through a simple modification of the material.

Microstructures of Binary Oxides with an Inverse Opal Structure Used as Photoelectrodes for Water Splitting

“…Nickel sulfide is a p-type semiconductor [97]. Metallic sulfides are attractive because of their abundance in the earth, cheap, active in visible light, and small bandgap [98].…”

“…39 shows that NiO is a p-type semiconductor with a band gap between 3.15 and 3.8 eV [160] and a Fermi energy of -0.955 eV [161]. The conduction band has a value of -0.5 V and the valence band of 2.93 V [97]. For the hydrogen evolution reaction, it is observed how a two-step process is involved on the surface of the NiO electrode, first the Volmer reaction:…”

Solar-Driven Photoreactor for Water Remediation Based on n-Type TiO2 and p-Type Ag/AgBiW2O8/Bi2WO6 Light-Responsive Air-Fed Gas Diffusion Electrodes

“…Furthermore, its valence band edge has appropriate energy values for the decomposition of water, thus generating hydroxyl radicals and other highly oxidizing species, intermediates in the oxygen evolution reaction . The TiO 2 photoanode has been used for degradation of several contaminants of emerging concern, phenol (a common compound in effluents of several industries), pharmaceuticals, , atrazine, and also for water disinfection …”