Single-Atom Co─O 4 Sites Embedded in a Defective-Rich Porous Carbon Layer for Efficient H 2 O 2 Electrosynthesis.

The production of hydrogen peroxide (H 2 O 2 ) 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─O 4 electrocatalyst is embedded in a defective and porous graphene-like carbon layer (Co─O 4 @PC). The Co─O 4 @PC electrocatalyst shows promising potential in H 2 O 2 electrosynthesis via 2e - ORR, providing a high H 2 O 2 selectivity of 98.8% at 0.6 V and a low onset potential of 0.73 V for generating H 2 O 2 . 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─O 4 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─O 4 @PC as the cathode present long-term stability and high efficiency for H 2 O 2 production. Particularly, a high H 2 O 2 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 H 2 O 2 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 H 2 O 2 by using Co─O 4 single atom electrocatalyst and unveil the electrocatalytic mechanism.