The efficient removal of organic micropollutants remains a major challenge for conventional water treatment technology. Photocatalysis, while effective, has not been widely adopted due to cost and implementation challenges. Here, an effective alternative is proposed through the integration of photocatalytic and electrochemical degradation of tetracycline (TC) in a continuous flow reactor using a WO3/W mesh as photo-electrode. WO3 nanoporous structures were grown on a tungsten (W) metal mesh via one step anodization in aqueous oxalic acid electrolyte (0.05 mol/L). The prepared materials were then used as 3D array photoanode in a continuous flow photo-electrocatalytic reactor. The combined influence of anodization time and post-treatment annealing temperature on the photo-electrochemical activity of the WO3/W mesh was examined through morphological and structural analysis. W mesh anodized for 4 h, and subsequently annealed at 450 °C have a homogenous nanoporous structure uniformly distributed and well adhering onto the W mesh, with average pore diameter of ∼ 80 nm and pore wall thickness of ∼ 250 nm. These materials are transparent, have high conductivity and WO3 monoclinic phase. Under optimal conditions of recirculating flow rate of 230 mL min−1 and bias potential of + 1.0 V vs Ag/AgCl/KCl (3 mol/L), the photo-electrocatalytic degradation led to a TC removal of up to 90 % after 60 min of treatment, almost 3 times higher than photocatalysis only. The excellent results by integration of photocatalysis and electrochemical degradation in a flow reactor, combined with a scalable WO3/W mesh, offers a useful information for upscaling and designing for practical issues in water treatment (such as costs and efficiency).

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 (Ni0), 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/Ni0 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.