Single-Atom Co─O4 Sites Embedded in a Defective-Rich Porous Carbon Layer for Efficient H2 O2 Electrosynthesis.

The production of hydrogen peroxide (H2 O2 ) via the two-electron electrochemical oxygen reduction reaction (2e- ORR) is an essential alteration in the current anthraquinone-based method. Herein, a single-atom Co─O4 electrocatalyst is embedded in a defective and porous graphene-like carbon layer (Co─O4 @PC). The Co─O4 @PC electrocatalyst shows promising potential in H2 O2 electrosynthesis via 2e- ORR, providing a high H2 O2 selectivity of 98.8% at 0.6 V and a low onset potential of 0.73 V for generating H2 O2 . In situ surface-sensitive attenuated total reflection Fourier transform infrared spectra and density functional theory calculations reveal that the electronic and geometric modification of Co─O4 induced by defective carbon sites result in decreased d-band center of Co atoms, providing the optimum adsorption energies of OOH* intermediate. The H-cell and flow cell assembled using Co─O4 @PC as the cathode present long-term stability and high efficiency for H2 O2 production. Particularly, a high H2 O2 production rate of 0.25 mol g-1 cat  h-1 at 0.6 V can be obtained by the flow cell. The in situ-generated H2 O2 can promote the degradation of rhodamine B and sterilize Staphylococcus aureus via the Fenton process. This work can pave the way for the efficient production of H2 O2 by using Co─O4 single atom electrocatalyst and unveil the electrocatalytic mechanism.