Tetrabromobisphenol A Degradation by a Photoelectrocatalytic System with a Carbon Layer-Protected Cuprous Oxide Cathode: Performance and Promoting Mechanism

Tetrabromobisphenol A (TBBPA), as the most widely used brominated flame retardant, was characterized by its recalcitrance to degradation and bioaccumulation. To address this limitation, a carbon layer-protected Cu₂O (C-Cu₂O/Cu) cathode was fabricated via in-situ chemical oxidation and calcination followed by glucose impregnation-carbonization, which was subsequently coupled with silver-loaded TiO₂ (Ag-TiO₂/Ti) anode prepared by anodic oxidation and photodeposition to construct an efficient photoelectrocatalytic (PEC) system. By optimizing preparation parameters such as impregnation concentration and calcination temperature, the photocurrent density of the C-Cu₂O/Cu cathode was enhanced to 2.6 times higher than that of Cu₂O/Cu, and it maintained stable performance during 1200 s of light on/off cycles, contrasting with the rapid decay of Cu₂O/Cu. Within the PEC system, the C-Cu₂O/Cu photocathode achieved a TBBPA degradation efficiency of 97.1%, significantly surpassing the 87.2% of Cu₂O/Cu. Systematic investigation of various applied voltages, pH levels, and electrolyte concentrations revealed that the optimal operating parameters were a 1.5 V bias, pH 9.5 and 0.05 mol/L Na₂SO₄. Radical trapping experiments confirmed that hydroxyl radicals (·OH) and superoxide radicals (·O₂⁻) served as the primary reactive species, while GC–MS analysis elucidated the degradation pathway involving debromination, ring cleavage, and mineralization. This study provided a novel strategy for enhancing the stability of Cu₂O photoelectrodes and achieving efficient degradation of persistent organic pollutants with the PEC system.