Highly efficient electrochemical generation of H2O2 on N/O co-modified defective carbon

Abstract

The electrochemical oxygen reduction reaction (ORR) via two-electron pathway is a sustainable way of producing hydrogen peroxide. Nanostructured carbon materials are proved to be effective catalysts for 2e− ORR. Herein, a series of mesoporous carbon with tunable nitrogen species and oxygen functional groups were synthesized by varying the added amount of dopamine hydrochloride as nitrogen and oxygen source. The modified catalysts exhibited higher content of pyrrolic-N and ether C–O groups which are confirmed by a series of characterization. Raman spectra and correlation analysis revealed that the increased proportion of defect sites in carbon materials are closely related to the introduced pyrrolic-N and ether C–O groups. And the rotating ring-disk electrode (RRDE) measurement carried out in 0.1 M KOH electrolyte showed the H2O2 selectivity increased with the content of defect sites. Among them, the optimized catalyst (NOC-6M) exhibited a selectivity of 95.2% and a potential of 0.71 V vs. RHE at −1 mA cm−2. Moreover, NOC-6M possessed the high H2O2 production rate of 548.8 mmol gcat−1 h−1 with faradaic efficiency of 92.4% in a two-chamber H-cell. Further mechanistic analysis revealed that the introduction of pyrrolic-N and ether C–O are likely to improve the binding energy of the defect sites toward ∗OOH intermediate, resulting in a more favorable 2e− ORR pathway for H2O2 production.