Single-Atom CoDO₄ 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 & horbar;O-4 electrocatalyst is embedded in a defective and porous graphene-like carbon layer (Co & horbar;O-4@PC). The Co & horbar;O-4@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 & horbar;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 & horbar;O-4@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(cat)(-1) 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 & horbar;O-4 single atom electrocatalyst and unveil the electrocatalytic mechanism.