Activation of chloride by oxygen vacancies-enriched TiO2 photoanode for efficient photoelectrochemical treatment of persistent organic pollutants and simultaneous H2 generation

Photoelectrochemical (PEC) activation of chloride ions (Cl - ) to degrade persistent organic pollutants (POPs) is a promising strategy for the treatment of industrial saline organic wastewater. However, the wide application of this technology is greatly restricted due to the general photoanode activation of Cl - with poor capability, the propensity to produce toxic by-products chlorates, and the narrow pH range. Herein, oxygen vacancies-enriched titanium dioxide (O v -TiO 2 ) photoanode is explored to strongly activate Cl - to drive the deep mineralization of POPs wastewater in a wide pH range (2−12) with simultaneous production of H 2 . More importantly, nearly no toxic by-product of chlorates was produced during such PEC-Cl system. The degradation efficiency of 4-CP and H 2 generation rate by O v -TiO 2 were 99.9% within 60 min and 198.2 μmol h −1 cm −2 , respectively, which are far superior to that on the TiO 2 (33.1% within 60 min, 27.5 μmol h −1 cm −2 ) working electrode. DFT calculation and capture experiments revealed that O v -TiO 2 with abundant oxygen vacancies is conducive to the activation of Cl - to produce more reactive chlorine species, evidenced by its high production of free chlorine (48.7 mg L −1 vs 7.5 mg L −1 of TiO 2 ). The as-designed PEC-Cl system in this work is expected to realize the purification of industrial saline organic wastewater coupling with green energy H 2 evolution.