Fabrication of sulfur-doped TiO₂ nanotube array as a conductive interlayer of PbO₂ anode for efficient electrochemical oxidation of organic pollutants

Efficient and stable anode materials are in high demand for the electrochemical oxidation of toxic and persistent organic pollutants in wastewater treatment. Herein, a highly structured and conductive sulfur-doped TiO₂ nanotubes was fabricated as an interlayer for the Ti-based PbO₂ anode (S-TiO₂ NTA-PbO₂). The novel S-TiO₂ NTA-PbO₂ anode exhibited a better electrochemical oxidation capability and hydroxyl radical production activity for organic degradation than the parent interlayer-based anode without S-doping and the well-reported PbO₂ anode. A nearly 100% of methylene blue (MB, 20 mg L^-1) was degraded on the S-TiO₂ NTA-PbO₂ anode in 90 min. A quenching experiment revealed that direct oxidation on the anode surface contributed about 50% of the MB degradation and played a crucial role in the complete mineralization of MB. The stable and conductive S-TiO₂ NTA interlayer enabled the high reactivity and stability of the composite anode, as exhibited by the cyclic tests. Moreover, the S-TiO₂ NTA-PbO₂ anode was versatile enough to degrade various industrial pollutants, including 4-chlorophenol, p-nitrophenol and bisphenol A. This work on the new conductive S-doped TiO₂ NTA interlayer also provides a new method for the design and fabrication of highly effective and stable anodes for electrochemical treatment of industrial wastewater.