Insights into the Electrochemical Production of Hydrogen Peroxide over Single-Atom Co-N-C Catalysts with the Introduction of Carbon Vacancy Defect near the Co-N 4 Site.

With the introduction of carbon divacancy, trivacancy, and tetravacancy defects near the Co-N 4 site, we have explored the 2e - ORR activity at the Co-N 4 site from the perspective of spatial structure and the atomic orbital by DFT calculations. We demonstrate the hybridization strength between Co 3dyz (3dxz) and O 2py (2px) orbitals is the origin of 2e - ORR activity at the Co-N 4 site and the hybridization strength relates to the height of the Co 3d projected orbital in the Z direction. The bond length (L Co-O , L O-O ), the charge transfer from the Co site to the *OOH adsorbate (ΔQ Co-O ), the d-band center of the Co site (ε d ), and the ICOHP value between Co 3d and O 2p orbitals as descriptors can well predict the 2e - ORR activity at the Co-N 4 site. This work provides original insights into the 2e - ORR activity over the single-atom Co-N-C catalysts.