Decoding active sites in metal-free N-doped carbon electrocatalysts for oxygen reduction reaction via in situ synchrotron near-ambient pressure XPS
(2026) In Carbon 255.- Abstract
Metal-free nitrogen-doped carbon materials are promising electrocatalysts towards oxygen reduction reaction (ORR), yet the nature of the active sites remains under debate. Previous investigations based on ex situ X-ray photoelectron spectroscopy (XPS) characterization and computational modelling studied the role of graphitic N species in ORR and suggested that these species at the carbon edges are the most active site towards ORR in alkaline conditions and pyridone type groups (N-C-O) may be formed as ORR intermediates. However, these findings are limited by the ex situ XPS measurement approach. Air exposure and vacuum treatment can alter oxidation states and surface adsorbates, hindering direct correlation with electrochemical... (More)
Metal-free nitrogen-doped carbon materials are promising electrocatalysts towards oxygen reduction reaction (ORR), yet the nature of the active sites remains under debate. Previous investigations based on ex situ X-ray photoelectron spectroscopy (XPS) characterization and computational modelling studied the role of graphitic N species in ORR and suggested that these species at the carbon edges are the most active site towards ORR in alkaline conditions and pyridone type groups (N-C-O) may be formed as ORR intermediates. However, these findings are limited by the ex situ XPS measurement approach. Air exposure and vacuum treatment can alter oxidation states and surface adsorbates, hindering direct correlation with electrochemical performance. In addition, short-lived reaction intermediates that form under in situ conditions are inherently transient and are therefore not captured by ex situ measurements, leading to an incomplete representation of the active surface during electrochemical operation. Sensitivity of the ex situ XPS can also be a challenge. To overcome these limitations, we report the first in situ investigation of N-doped metal free electrocatalysts using near-ambient pressure XPS (NAP-XPS) under highly controlled electrochemical conditions at a synchrotron source. This in situ approach enables the dynamic evolution of nitrogen species as a function of applied potential and electrolyte environment (acidic and alkaline) under close to realistic ORR conditions, allowing previously proposed active-site assignments to be critically evaluated. The use of this technique opens the door to studying carbon-based electrocatalysts with different functionalities under operating conditions, with the aim of gaining a more detailed understanding of the reaction mechanism.
(Less)
- author
- Morallón, Emilia ; Alemany-Molina, Gabriel ; Urpelainen, Samuli LU ; Ghosalya, Manoj ; Shavorskiy, Andrey LU ; Calabuig-Mompó, Samuel ; García-Santos, Lidia and Cazorla-Amorós, Diego
- organization
- publishing date
- 2026-05-05
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Carbon
- volume
- 255
- article number
- 121563
- publisher
- Elsevier
- external identifiers
-
- scopus:105035299571
- ISSN
- 0008-6223
- DOI
- 10.1016/j.carbon.2026.121563
- language
- English
- LU publication?
- yes
- id
- 3547feb0-eb2c-4903-8523-9a6c41483bde
- date added to LUP
- 2026-07-06 14:28:51
- date last changed
- 2026-07-06 14:29:38
@article{3547feb0-eb2c-4903-8523-9a6c41483bde,
abstract = {{<p>Metal-free nitrogen-doped carbon materials are promising electrocatalysts towards oxygen reduction reaction (ORR), yet the nature of the active sites remains under debate. Previous investigations based on ex situ X-ray photoelectron spectroscopy (XPS) characterization and computational modelling studied the role of graphitic N species in ORR and suggested that these species at the carbon edges are the most active site towards ORR in alkaline conditions and pyridone type groups (N-C-O) may be formed as ORR intermediates. However, these findings are limited by the ex situ XPS measurement approach. Air exposure and vacuum treatment can alter oxidation states and surface adsorbates, hindering direct correlation with electrochemical performance. In addition, short-lived reaction intermediates that form under in situ conditions are inherently transient and are therefore not captured by ex situ measurements, leading to an incomplete representation of the active surface during electrochemical operation. Sensitivity of the ex situ XPS can also be a challenge. To overcome these limitations, we report the first in situ investigation of N-doped metal free electrocatalysts using near-ambient pressure XPS (NAP-XPS) under highly controlled electrochemical conditions at a synchrotron source. This in situ approach enables the dynamic evolution of nitrogen species as a function of applied potential and electrolyte environment (acidic and alkaline) under close to realistic ORR conditions, allowing previously proposed active-site assignments to be critically evaluated. The use of this technique opens the door to studying carbon-based electrocatalysts with different functionalities under operating conditions, with the aim of gaining a more detailed understanding of the reaction mechanism.</p>}},
author = {{Morallón, Emilia and Alemany-Molina, Gabriel and Urpelainen, Samuli and Ghosalya, Manoj and Shavorskiy, Andrey and Calabuig-Mompó, Samuel and García-Santos, Lidia and Cazorla-Amorós, Diego}},
issn = {{0008-6223}},
language = {{eng}},
month = {{05}},
publisher = {{Elsevier}},
series = {{Carbon}},
title = {{Decoding active sites in metal-free N-doped carbon electrocatalysts for oxygen reduction reaction via in situ synchrotron near-ambient pressure XPS}},
url = {{http://dx.doi.org/10.1016/j.carbon.2026.121563}},
doi = {{10.1016/j.carbon.2026.121563}},
volume = {{255}},
year = {{2026}},
}