Understanding the selectivity trend of water and sulfate (SO42−) oxidation on metal oxides: On-site synthesis of persulfate, H2O2 for wastewater treatment

Herein, H 2 O 2 production activity via two-electron water oxidation reaction is identified on metal oxides (WO 3 , TiO 2 , and BiVO 4 ) in acidic SO 4 2− involving electrolyte, in which persulfate (PS) acts as an intermediate. A deep understanding of mechanism of PS production reaction on metal oxides has been realized based on rigorous crystal plane analysis of WO 3 and TiO 2 by combining density functional theory calculations and zeta potential measurements. It is found that the binding-energy of adsorbed hydroxyl groups on dominant exposed crystal plane of WO 3 is lower than that of TiO 2 , leading to more SO 4 2− adsorption sites at the surface of WO 3 . Consequently, the formation of PS on WO 3 surface is more favorable. Meanwhile, both SO 4 − · and OH· were detected in the electrolyte by electron paramagnetic resonance measurement, which play a crucial role in organic pollutants wastewater treatment, with a degradation efficiency of 96% in 90 min for a typical pollutant norfloxacin. This work can provide a novel insight for understanding the selectivity of water and SO 4 2− species oxidation on metal oxides, and open a new way for both on-site H 2 O 2 production and advanced oxidation processes application.