Pulsed Electrocatalysis Enables Efficient Three-Electron Oxygen Reduction to Hydroxyl Radicals.

Overcoming mass transfer and slow intermediate conversion bottlenecks for efficient three-electron oxygen reduction reaction (3e- ORR) remains a key challenge in green water treatment development. This study breaks away from direct-current (DC) electrocatalysis by introducing a pulsed electrochemical modulation strategy on the Cu1Bi@C catalyst. Through periodic perturbation of the electrode interface, the 3e- ORR pathway is reinforced, increasing hydroxyl radical (·OH) yield by 2.38-fold, bisphenol A (BPA) rate by 2.5-fold, demonstrating superior deep-pollutant removal capability. The study reveals that pulsed potential enhances the three-step process from O2 reduction to hydrogen peroxide (H2O2), ·OH generation, and pollutant mineralization. During the pulse-on stage, O2 gains an electron and couples with a proton on Bi sites to form the key intermediate Bi⋯*OOH, which desorbs and further reacts to produce H2O2. Simultaneously, the in situ-generated H2O2 rapidly accepts an electron on neighboring single-atom Cu sites, converting into ·OH to mineralize pollutants efficiently. The pulsed potential not only reduces concentration polarization and enhances reactant supply and product release, but also accelerates H+ transfer and its coupling with O═O/O─O bonds. This work provides a new methodology and theoretical foundation for understanding 3e- ORR and its environmental applications.