Superior Singlet Oxygen Electrosynthesis via Neighboring Dual Molecular Oxygen Coactivation for Selective...

Oxygen (O₂) electroreduction offers a green approach for singlet oxygen (¹O₂) synthesis in wastewater contaminants detoxification. However, traditional single O₂ activation on single-metal catalytic sites seriously suffers from the kinetically-unfavorable desorption of adsorbed superoxide species (•O₂ ^-*/•OOH*). Here, we demonstrate a novel dual O₂ coactivation pathway on shortened Fe₁-O_V-Ti sites for superior ¹O₂ electrosynthesis through a rapid disproportionate process between surface-confined •O₂ ^-*/•OOH*. Theoretical calculations combined with in situ electrochemical spectroscopies demonstrated that the shortened distance between Fe single atom and adjacent unsaturated Ti atom facilitates the direct recombination of surface-confined Fe-•OOH and Ti-•OO^- to yield ¹O₂, bypassing the formidable •O₂ ^-*/•OOH* desorption process. Impressively, Fe₁-O_V-Ti could realize an excellent ¹O₂ electrosynthesis rate of 54.5 μmol L^-1 min^-1 with an outstanding ¹O₂ selectivity of 97.6 % under neutral condition, surpassing that of Fe₁-O-Ti (27.1 μmol L^-1 min^-1, 91.7 %). Using tetracycline (TC) as a model pollutant, the resulting Fe₁-O_V-Ti electrode achieved nearly 100 % degradation in 120 min at -0.6 V, meanwhile preventing the generation of toxic intermediates. This study provides a new ¹O₂ electrosynthesis strategy by controlling the distance of adjacent catalytic sites for the coactivation of dual molecular oxygen.