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

The production of hydrogen peroxide (HO) 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 electrocatalyst is embedded in a defective and porous graphene-like carbon layer (Co─O@PC). The Co─O@PC electrocatalyst shows promising potential in HO electrosynthesis via 2e ORR, providing a high HO selectivity of 98.8% at 0.6 V and a low onset potential of 0.73 V for generating HO. 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 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@PC as the cathode present long-term stability and high efficiency for HO production. Particularly, a high HO production rate of 0.25 mol g  h at 0.6 V can be obtained by the flow cell. The in situ-generated HO 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 HO by using Co─O single atom electrocatalyst and unveil the electrocatalytic mechanism.