Sb-doped SnO2 nanoflowers/Ti/TiO2-nanotubes bifacial electrode for enhanced photoelectrocatalytic degradation of p-nitrophenol.

The environmental persistence and acute toxicity of p-nitrophenol (p-NP) necessitate the development of advanced treatment strategies that surpass conventional approaches. In this work, a novel bifacial photoelectrocatalytic (PEC) anode was constructed by integrating Sb-doped SnO2 nanoflowers (Sb-SnO2 NFs) and TiO2 nanotube arrays (TiO2 NTs) on opposite surfaces of a titanium substrate, thereby coupling electrocatalytic and photocatalytic functionalities within a single architecture. The optimal electrode, prepared via anodization at 60 V, exhibited superior charge carrier separation and reduced interfacial resistance, resulting in the efficient generation of hydroxyl radicals (·OH). Consequently, it achieved 97.62 % removal of p-NP and a 75.23 % reduction in total organic carbon (TOC) within 1 h of PEC operation. Mechanistic investigations through electron paramagnetic resonance (EPR) and radical quenching experiments confirmed ·OH and superoxide radicals (O2·-) as the predominant reactive species. GC-MS analysis identified distinct degradation pathways, while toxicity evaluation based on the Ecological Structure Activity Relationship (ECOSAR) model revealed a substantial decrease in the ecological risk of p-NP and its transformation products. Additionally, the electrode demonstrated excellent structural integrity and catalytic stability over ten consecutive PEC cycles. These findings highlight the great promise of bifacial PEC electrode designs in achieving efficient and long-term treatment of persistent organic contaminants in water systems.