Steering two-electron O2 electroreduction on a Co–N–C catalyst via native carbon-defect engineering for highly efficient H2O2 production

Abstract

Traditional Co–N–C electrocatalysts have considerable potential in the two-electron oxygen reduction reaction (2e⁻ ORR), but their robust binding to the critical *OOH intermediate largely hinders their selectivity for H₂O₂ production. In this study, pentagonal carbon defects were deliberately introduced into a Zn/Co-ZIF-derived Co–N–C electrocatalyst (D-Co–N–C-X) via a facile thermal etching method to significantly modulate the electronic configuration and adsorption strength of the Co center, thereby enhancing its 2e⁻ ORR selectivity and H₂O₂ yield. Moreover, the carbon defect content was adjusted to examine its effect on the catalytic performance in D-Co–N–C-X. Results showed that the D-Co–N–C-2 with moderate intrinsic defects performed best with a high H₂O₂ selectivity (H₂O₂%) of 91%, impressive faradaic efficiency (FE) of 99% and superior H₂O₂ yield of 934 mmol g⁻¹ h⁻¹, significantly surpassing the values for defect-free Co–N–C (H₂O₂%: 37%, FE: 11%, and H₂O₂ yield: 101 mmol g⁻¹ h⁻¹) and the reported state-of-the-art electrocatalysts under acidic conditions. Moreover, the D-Co–N–C-2 showed long-term operational stability and high performance for the electro-Fenton degradation of typical organic chemicals. Both experimental results and theoretical calculations confirmed that the incorporated pentagonal defects not only reduced the electron density around the Co center and upshifted its d-band center for favorable O₂ adsorption but also decreased the *OOH desorption energy for H₂O₂ formation, thus significantly improving the electrocatalytic 2e⁻ ORR performance. This study advances a new strategy for developing high-performance Co–N–C-based electrocatalysts towards in situ H₂O₂ synthesis for environmental remediation.