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

Oxygen (O) electroreduction offers a green approach for singlet oxygen (O) synthesis in wastewater contaminants detoxification. However, traditional single O activation on single-metal catalytic sites seriously suffers from the kinetically-unfavorable desorption of adsorbed superoxide species (•O /•OOH). Here, we demonstrate a novel dual O coactivation pathway on shortened Fe-O-Ti sites for superior O electrosynthesis through a rapid disproportionate process between surface-confined •O /•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 O, bypassing the formidable •O /•OOH desorption process. Impressively, Fe-O-Ti could realize an excellent O electrosynthesis rate of 54.5 μmol L min with an outstanding O selectivity of 97.6 % under neutral condition, surpassing that of Fe-O-Ti (27.1 μmol L min, 91.7 %). Using tetracycline (TC) as a model pollutant, the resulting Fe-O-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 O electrosynthesis strategy by controlling the distance of adjacent catalytic sites for the coactivation of dual molecular oxygen.