Subsurface Graphitic Nitrogen Activates Protonated Pyridinic‐N Sites for Acidic Oxygen Reduction

Authors:
Publisher website
Google Scholar
Abstract
Protonation of pyridinic nitrogen (pyri‐N) sites in nitrogen‐doped carbon catalysts under acidic conditions converts pyri‐N to pyri‐NH + , leading to severe catalytic deactivation. Restoring activity requires transforming pyri‐NH + back to pyri‐NH, an energetically demanding process that limits oxygen reduction reaction (ORR) efficiency. To overcome this challenge, we developed an N‐doped porous carbon catalyst (NpC‐7) featuring surface pyri‐N active sites and a subsurface graphitic nitrogen (grap‐N) layer. The 2D growth of cyanuric acid (CA)‐functionalized 2‐hydroxyethyl methacrylate (HEMA) polymer within graphene oxide layers ensures uniform N‐doping which modulates π‐electron and spin states. This engineered architecture delivers ORR activity approaching Pt/C and surpasses conventional nitrogen doped graphene oxide (NrGO) ( E onset = 0.86 V, E 1/2 = 0.70 V vs. 0.76 and 0.61 V, respectively). Enhanced performance arises from subsurface grap‐N, which donates electron to protonated pyri‐NH + , generating an active pyri − NH δ + state that promotes O 2 adsorption. In situ electrochemical Raman spectroscopy and density functional theory (DFT) calculations confirm efficient O 2 adsorption and intermediate formation, indicating a (2 + 2)e − ORR pathway. These findings highlight the critical role of subsurface grap‐N in overcoming acidic deactivation through electronic modulation, offering a blueprint for designing acid‐stable carbon electrocatalysts.
Funding Information
  • Shiv Nadar Foundation

This publication has 35 references indexed in Scilit: