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

The development of an effective cocatalyst for the modification of TiO2 arrays has become highly desirable for the improvement of their photoelectrocatalytic properties. We investigated the modification of TiO2 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/TiO2/NiO and Ti/TiO2/NiS and the generation of Schottky-type barrier for the Ti/TiO2/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/TiO2/NiS photocurrent was found to be almost two times higher than that of the Ti/TiO2 (5.39 mA.cm(-2) at +1.50 V); this result was attributed to the excellent distribution of the cocatalyst around the TiO2 nanotube walls, which helped enhance the chemical interaction on the TiO2/NiS interface. Under optimized conditions (+0.50 V and UV-vis irradiation), the application of the Ti/TiO2/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/TiO2 through a simple modification of the material.