Electrode configuration engineering in a photocatalytic fuel cell for enhanced dye removal and electricity generation

Photocatalytic fuel cells (PFCs) enable simultaneous wastewater treatment and energy recovery. This study systematically investigated the spatial configuration of electrodes—position, orientation, and distance—in a multi-electrode PFC. Anodic TiO₂ nanotube arrays (TNAs/Ti) and cathodic CuO/Cu, both synthesized via anodization, were arranged in six different configurations (S1–S6) and evaluated for acid orange 7 (AO7) removal and electricity generation. The results demonstrated that the heterogeneous configurations (S1 and S3) induced reverse currents from stronger to weaker anodes, which accelerated electron-hole recombination and increased the internal resistance to 600 Ω. In contrast, the homogeneous configuration (S5) minimized the average anode-cathode distance to 5.8 cm, suppressed reverse currents, and enhanced charge separation. This optimized configuration achieved 94.1 % decolorization over 16 h with a pseudo-first-order rate constant of 0.182 h⁻¹, a maximum power density of 11.6 mW m⁻², a short-circuit current density of 131 mA m⁻², and an internal resistance of 300 Ω. Performance was further enhanced under optimal conditions, including 50 mg L⁻¹ AO7, 0.1 M Na₂SO₄ electrolyte, pH 5.0, and 1000 Ω external resistance. Radical scavenging tests identified sulfate (SO₄·⁻), superoxide (Ȯ₂⁻), and hydroxyl (ȮH) radicals as primary reactive species with contributions of 35.4 %, 35.0 % and 24.9 %, respectively. Mineralization analyses confirmed 66.7 % COD and 50.5 % TOC removal, with the average oxidation state increasing from −1.4 to 0.4. The system maintained an efficiency of 94.1 % after 20 cycles, with negligible corrosion. These findings indicate that electrode configuration engineering is a crucial strategy for enhancing PFC efficiency.