Single-Atom Co─O₄ Sites Embedded in a Defective-Rich Porous Carbon Layer for Efficient H₂O₂ Electrosynthesis

The production of hydrogen peroxide (H₂O₂) 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 H₂O₂ electrosynthesis via 2e^- ORR, providing a high H₂O₂ selectivity of 98.8% at 0.6 V and a low onset potential of 0.73 V for generating H₂O₂. 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 H₂O₂ production. Particularly, a high H₂O₂ 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 H₂O₂ 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 H₂O₂ by using Co─O₄ single atom electrocatalyst and unveil the electrocatalytic mechanism.