Metal‐Free Electrocatalysts for the Selective 2 e−Oxygen Reduction Reaction: A Never‐Ending Story?

Abstract

AbstractHydrogen peroxide (H2O2) electrosynthesis via the 2e−Oxygen Reduction Reaction (ORR) represents a highly challenging, environmentally friendly and cost‐effective alternative to the current anthraquinone‐based technology. Various lightweight element hetero‐doped carbon nanostructures are promising and cheap metal‐free electrocatalysts for H2O2synthesis, particularly those containing O‐functionalities. The exact role of O‐containing functional groups as electroactive sites for the process remains debated if not highly controversial. Herein, we have reported on the covalent exohedral functionalization of the outer surface of extra‐pure multi‐walled carbon nanotubes (MWCNTs) with discrete O‐functional groups as a unique approach to prepare selective electrocatalysts for the process. This kind of decoration has added fundamental tiles to the puzzling structure/reactivity relationship of O‐containing carbon‐based catalysts for ORR, clearing doubts on the controversial role of hydroxyl/phenol groups as key functionalities for the design of more performing 2e−ORR electrocatalysts.