Impact of Pore Structure on Two-Electron Oxygen Reduction Reaction in Nitrogen-Doped Carbon Materials: Rotating Ring-Disk Electrode vs. Flow Cell

Abstract

The impact of pore structure on the two-electron oxygen reduction reaction (ORR) in nitrogen-doped carbon materials is currently under debate, and previous studies are mainly limited to the rotating ring-disk electrode (RRDE) rather than the practical flow cell (FC) system. In this study, assisted by a group of reliable pore models, the impact of two pore structure parameters, that is, Brunauer-Emmett-Teller surface area (S_BET ) and micropore surface fraction (f_micro ), on ORR activity and selectivity are investigated in both RRDE and FC. The ORR mass activity correlates positively to the S_BET in the RRDE and FC because a higher S_BET can host more active sites. The H₂ O₂ selectivity is independent of f_micro in the RRDE but correlates negatively to f_micro in the FC. The inconsistency results from different states of the electrode in the RRDE and the FC. These insights will guide the design of carbon materials for H₂ O₂ synthesis.

Keywords: electrocatalysis; electrosynthesis; hydrogen peroxide; oxygen reduction reaction; porous materials.