Synergistic Effects in N,O-Comodified Carbon Nanotubes Boost Highly Selective Electrochemical Oxygen Reduction to H2O2

Electrochemical 2-electron oxygen reduction reaction (ORR) is a promising route for renewable and on-site H2O2 production. Oxygen-rich carbon nanotubes have been demonstrated their high selectivity (approximate to 80%), yet tailoring the composition and structure of carbon nanotubes to further enhance the selectivity and widen working voltage range remains a challenge. Herein, combining formamide condensation coating and mild temperature calcination, a nitrogen and oxygen comodified carbon nanotubes (N,O-CNTs) electrocatalyst is synthesized, which shows excellent selective (>95%) H2O2 selectivity in a wide voltage range (from 0 to 0.65 V versus reversible hydrogen electrode). It is significantly superior to the corresponding selectivity values of CNTs (approximate to 50% in 0-0.65 V vs RHE) and O-CNTs (approximate to 80% in 0.3-0.65 V vs RHE). Density functional theory calculations revealed that the C neighbouring to N is the active site. Introducing O-related species can strengthen the adsorption of intermediates *OOH, while N-doping can weaken the adsorption of in situ generated *O and optimize the *OOH adsorption energy, thus improving the 2-electron pathway. With optimized N,O-CNTs catalysts, a Janus electrode is designed by adjusting the asymmetric wettability to achieve H2O2 productivity of 264.8 mol kg(cat)(-1) h(-1).

Automated summary

In this study, a nitrogen and oxygen co-modified carbon nanotubes (N, O-CNTs) electrocatalyst with excellent H2O2 selectivity in a wide voltage range was successfully synthesized. It outperformed other carbon nanotube materials and the mechanism for its active sites and improvement of the 2-electron pathway was revealed through theoretical calculations.