Si/Carbon‐dots with Surface N‐C Sites Promoting Proton and Electron Transfers in Oxygen Reduction Reaction

Abstract

Abstract The oxygen reduction reaction (ORR) can proceed through either a two‐ or four‐electron pathway, both of which are important for a wide range of applications. The intermediate conversion of *O 2 ⁻ + H⁺ → *OOH recognized as the rate‐determining step in ORR, with its efficiency strongly dependent on the nature of active sites at the surface of a catalyst. Herein, Si‐supported carbon dots (Si‐CDs) are introduced as cocatalysts in a photocatalytic system, where their nitrogen–carbon sites play a pivotal role in lowering the energy barrier for *OOH formation by promoting proton and electron transfers, thus enhancing the H 2 O 2 production rate in ORR. This strategy is broadly applicable across a wide range of photocatalysts, both with and without use of sacrificial agents. The H 2 O 2 production rate for Zn 0.5 Cd 0.5 S (30 mg) increased from 13.0 to 40.9 µmol h −1 when 0.6 mg of Si‐CDs were added. In‐situ characterizations and theoretical simulations are conducted to reveal the reaction pathway and the reduced energy requirements for the *O 2 ⁻ + H⁺ → *OOH conversion. This study provides a unique example of overcoming a key barrier in ORR using a metal‐free catalyst and promotes potential applications in various fields.