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Subsurface Graphitic Nitrogen Activates Protonated Pyridinic-N Sites for Acidic Oxygen Reduction
Dipti R Panigrahi1, Pranjit Barman1, Shouvik Mete1
1Department of Chemistry, School of Natural Sciences, Shiv Nadar Institution of Eminence, Gautam Buddha Nagar, Uttar Pradesh, India.
Small (Weinheim an Der Bergstrasse, Germany)
|May 13, 2026
Summary
We developed a novel nitrogen-doped porous carbon catalyst (NpC-7) that enhances oxygen reduction reaction (ORR) efficiency in acidic conditions. Subsurface graphitic nitrogen (grap-N) prevents deactivation by donating electrons to protonated sites, improving catalyst stability and performance.
Area of Science:
- Materials Science
- Electrochemistry
- Catalysis
Background:
- Protonation of pyridinic nitrogen (pyri-N) in nitrogen-doped carbon catalysts leads to deactivation in acidic media, limiting oxygen reduction reaction (ORR) efficiency.
- Reversing this protonation is energetically challenging, hindering catalyst performance.
Purpose of the Study:
- To engineer a novel nitrogen-doped porous carbon catalyst (NpC-7) that overcomes acidic deactivation and enhances ORR performance.
- To investigate the role of subsurface graphitic nitrogen (grap-N) in stabilizing pyridinic nitrogen (pyri-N) active sites.
Main Methods:
- Fabrication of NpC-7 using cyanuric acid (CA)-functionalized 2-hydroxyethyl methacrylate (HEMA) polymer within graphene oxide layers for uniform N-doping.
- Electrochemical characterization of ORR activity and stability in acidic conditions.
- In situ electrochemical Raman spectroscopy and density functional theory (DFT) calculations to elucidate reaction mechanisms.
Main Results:
- NpC-7 exhibited superior ORR activity (Eonset = 0.86 V, E1/2 = 0.70 V) compared to conventional nitrogen doped graphene oxide (NrGO).
- Subsurface grap-N was found to donate electrons to protonated pyri-NH+, generating a stabilized active state (pyri-NHδ+) that promotes O2 adsorption.
- DFT and spectroscopic analyses confirmed efficient O2 adsorption and intermediate formation, suggesting a (2 + 2)e- ORR pathway.
Conclusions:
- The engineered NpC-7 catalyst demonstrates remarkable acid stability and enhanced ORR performance due to the electronic modulation effect of subsurface grap-N.
- This work provides a strategic approach for designing robust, acid-stable carbon electrocatalysts by leveraging subsurface nitrogen doping.
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