Ethylene Glycol\n(EG)-Derived Chlorine-Resistant Cu<sup>0</sup>/TiO<sub>2–<i>x</i></sub> for Efficient Photocatalytic\nDegradation of Nitrate to N<sub>2</sub> without Sacrificial Agents\nat Near-Neutral

The selective photoreduction of nitrate to nontoxic nitrogen\ngas\nhas emerged as an energy-efficient and environmentally friendly route\nfor nitrate removal. However, the coexisting high-concentration chloride\nions in wastewater can exert a significant influence on nitrate reduction\ndue to the competitive adsorption and corrosion of Cl<sup>–</sup> on photocatalysts. Herein, we prepared ethylene glycol-Cu/TiO<sub>2–<i>x</i></sub> (EG-Cu/TiO<sub>2–<i>x</i></sub>) through a solvothermal reaction of Cu-doped TiO<sub>2</sub> in an EG solution. The photodegradation of nitrate using\nEG-Cu/TiO<sub>2–<i>x</i></sub> without adding sacrificial\nagents can efficiently occur in near-neutral pH solutions containing\n50 mM Cl<sup>–</sup> with 95.26% of NO<sub>3</sub><sup>–</sup> removal and 76.52% of N<sub>2</sub> selectivity. Moreover, the photocatalyst\nperformance remained at a high level after 8 cycles. In this work,\nNO<sub>3</sub><sup>–</sup> was first converted to NH<sub>4</sub><sup>+</sup> by Cu<sup>0</sup> and Ti<sup>3+</sup>, followed by the\nNH<sub>4</sub><sup>+</sup>-to-N<sub>2</sub> conversion by photogenerated\nchlorine free radicals. Compared to HO<sup>•</sup>, Cl<sup>•</sup>, and Cl<sub>2</sub><sup>•–</sup>, ClO<sup><b>•</b></sup> is proved to play the predominant role\nin transforming NH<sub>4</sub><sup>+</sup> to N<sub>2</sub>. The EG\nradicals produced by UV light impede Cl<sup>–</sup> adsorption\non Cu, protecting Cu<sup>0</sup> from being corroded. What’s\nmore, photoelectrons can reduce Ti<sup>4+</sup> to Ti<sup>3+</sup> and protect Cu<sup>0</sup> from being oxidized, enabling the stability\nof reactive sites. This work provides novel insights and understanding\non designing photocatalysts for NO<sub>3</sub><sup>–</sup> removal\nin solutions containing chloride ions, highlighting the significance\nof eliminating Cl<sup>–</sup> by EG radicals and adjusting\nthe conversion process of NO<sub>3</sub><sup>–</sup> for the\nefficient removal of NO<sub>3</sub><sup>–</sup>.