Activating Oxygen via the 3‐Electron Pathway to Hydroxyl Radical by La‐O4 Single‐atom on WO3 for Water Purification

Shifting photocatalytic oxygen activation towards 3‐electron (e‐) pathway to hydroxyl radicals, instead of the normal 1 e‐ to superoxide radicals, becomes increasingly important for pollution degradation since hydroxyl radicals possess a high oxidation potential (2.80 V). Here, we demonstrate a selective oxygen activation to hydroxyl radicals via 3 e‐ pathway using single atomically dispersed La based on WO3 fabricated with oxygen vacancies to weaken La‐O coordination strength (denoted as LaO4‐WOv). Unsaturated‐state La overcomes the rate‐limited step of 2 e‐ oxygen reduction reaction towards to hydrogen peroxide via tuning binding free energy of key reaction intermediate *OOH, stepped by easy generation of hydroxyl radicals via 1 e‐. This strategy alters the activation of oxygen process from 1 e‐ to 3 e‐. Hydrogen peroxide and hydroxyl radicals over LaO4‐WOv produces 3.8 and 3.3 mmol L‐1 h‐1, 35 and 8 times that of detected over WO3, respectively. Rapid and complete removal of tetracycline realizes over LaO4‐WOv with 0.077 min‐1 of rate constant, 38 times that of WO3. Degradation efficiencies keep greater than 98% following five repeats, revealing a practical‐utilization‐level robust stability. This work builds an unsaturated‐state transition metal site for manipulating oxygen activation towards an effective water purification as a representative application.