Chlorine-doped ruthenium-cobalt oxide nanoparticles anchored tin-doped titanium dioxide nanowire array photoanode for synchronous ammonia oxidation and organic pollutant degradation.

Chlorine oxide radicals (ClO·) possess excellent application potential for the selective oxidation of ammonia and efficient degradation of organic pollutants. However, it remains challenging to attain high efficiencies for ClO· generation. In this study, a novel photoanode was prepared by anchoring Cl-doped Ru-Co oxide nanoparticles on Sn-doped TiO2 nanowire arrays (Sn-TiO2). Sn doping improved the photocatalytic activity and electrical conductivity of TiO2, and Cl doping optimized the chlorine evolution performance of Ru-Co oxide. Benefitting from these modifications, enhanced ammonia oxidation (96.6%), and ethylenediaminetetraacetic acid removal (99.4%) were obtained synchronously, accompanied by a chemical oxygen demand (COD) removal efficiency of 52.1% and a low NO3--N accumulation of 1.3 mg/L. The toxicity variation during the degradation process was evaluated, and chloramine could be effectively eliminated by appropriately extending the reaction time. The photoanode exhibited excellent application potential for actual electroplating tail wastewater treatment. Experimental results showed that 95.7% of NH4+-N and 89.4% of COD could be degraded within 140 min. Theoretical calculations confirmed that Cl doping enhanced Cl- adsorption on Ru/Co sites, facilitating chlorine evolution. Meanwhile, Sn-TiO2 promoted ·OH generation. Additionally, the inter-wire gaps of the nanowire arrays favored sufficient contact between free chlorine and ·OH. Consequently, the reaction between them was promoted and the generation of ClO· was boosted, ultimately improving pollutant degradation. This study develops a high-efficiency photoanode for enhanced ClO· production, which may contribute to the advancement of photoelectrocatalytic chlorination technology for water remediation.