Study on degradation of nitrobenzene in wastewater by in-situ deposited CdS/TiO2 heterojunction bipolar electrochemical-photoelectric synergistic system

Abstract

Nitrobenzene (NB), a toxic organic pollutant widely present in industrial wastewater, poses severe environmental risks due to its persistence and biological toxicity. Conventional treatment technologies suffer from inherent limitations, such as long biological treatment cycles, difficult adsorbent regeneration, and low efficiency of single-component photocatalysis caused by rapid recombination of photogenerated charge carriers. To address these challenges, we developed a bipolar electrochemical-photoelectric synergetic system based on in-situ deposited CdS/TiO₂ heterojunctions. The Z-scheme CdS/TiO₂ heterojunction, synthesized via a deposition method, exhibits enhanced visible-light absorption and accelerated separation of photogenerated carriers, both critical for enhancing catalytic activity. The bipolar electrochemical configuration enables semiconductor catalysts to exist in a suspended state, eliminating the constraint of electrode area, and operates at low electrolyte concentrations, thereby avoiding secondary pollution-a critical advantage over traditional photoelectrocatalytic systems. Under visible light irradiation, the synergetic system achieves exceptional NB degradation performance: with an applied bias of 10 V, 15 mmol/L NB is degraded by 99.13 % within 40 min, with aniline as the dominant product (selectivity 98.47 %). Notably, the system maintains stable activity over 10 consecutive cycles, demonstrating robust durability. This work highlights the synergistic merits of Z-scheme heterojunctions and bipolar electrochemistry, providing a promising strategy for industrial-scale degradation of NB in high-salinity wastewater.