Nanoporous WO₃ grown on a 3D tungsten mesh by electrochemical anodization for enhanced photoelectrocatalytic degradation of tetracycline in a continuous flow reactor

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).