---
_id: '64182'
abstract:
- lang: eng
text: Overcoming the slow kinetics of the oxygen evolution reaction at the anode
is a key challenge for the production of hydrogen via electrolysis. This reaction
operates at very positive potentials, where the electrocatalyst is exposed to
highly oxidative conditions and prone to potential-dependent transformation of
the near-surface region. While substantial evidence for such surface restructuring
exists, its extent and relevance for the catalyst’s activity are unclear. We address
this topic for the case of Co3O4, one of the best-known electrocatalysts exhibiting
surface restructuring, by studies of epitaxial (111)-ordered electrodeposited
films with combined operando X-ray surface diffraction and absorption spectroscopy,
electrochemical impedance spectroscopy, and electrochemical measurements on rotating
disk electrodes. Comparison of the as-prepared and annealed state of the same
samples, which both are stable even under long-term oxygen evolution conditions,
provides clear insight into the role of surface defects. Our results show that
defect-free annealed Co3O4(111) surfaces are structurally stable over a wide potential
range and hydroxylate via adsorption at surface oxygen and Co sites. Potential-induced
surface restructuring of the Co3O4 lattice occurs only in the presence of surface
defects, leading to the formation of the well-known nanometer-thick oxyhydroxide
skin layer. The presence of this skin layer promotes oxygen evolution at low overpotentials
but results in higher Tafel slopes. As a result, highly ordered Co3O4(111) surfaces
are more active at high current densities than defective Co3O4 surfaces that undergo
surface restructuring. These results highlight that strategies for catalyst surface
defect engineering need to be application-oriented.
article_number: acscatal.5c08785
article_type: original
author:
- first_name: Carl Hendric
full_name: Scharf, Carl Hendric
last_name: Scharf
- first_name: Alex
full_name: Chandraraj, Alex
last_name: Chandraraj
- first_name: Konrad
full_name: Dyk, Konrad
last_name: Dyk
- first_name: Felix
full_name: Stebner, Felix
last_name: Stebner
- first_name: Sören
full_name: Lepin, Sören
last_name: Lepin
- first_name: Jing
full_name: Tian, Jing
last_name: Tian
- first_name: Laila
full_name: El Bergmi Byaz, Laila
last_name: El Bergmi Byaz
- first_name: Jochim
full_name: Stettner, Jochim
last_name: Stettner
- first_name: Christian
full_name: Leppin, Christian
id: '117722'
last_name: Leppin
- first_name: Anastasiia
full_name: Kotova, Anastasiia
last_name: Kotova
- first_name: Sebastian
full_name: Reinke, Sebastian
id: '117727'
last_name: Reinke
- first_name: Julia
full_name: Linnemann, Julia
id: '116779'
last_name: Linnemann
orcid: 0000-0001-6883-5424
- first_name: Fouad
full_name: Maroun, Fouad
last_name: Maroun
- first_name: Olaf M.
full_name: Magnussen, Olaf M.
last_name: Magnussen
citation:
ama: Scharf CH, Chandraraj A, Dyk K, et al. Role of Defects in Reversible Surface
Restructuring and Activity of Co3O4 Oxygen Evolution Electrocatalysts.
ACS Catalysis. Published online 2026. doi:10.1021/acscatal.5c08785
apa: Scharf, C. H., Chandraraj, A., Dyk, K., Stebner, F., Lepin, S., Tian, J., El
Bergmi Byaz, L., Stettner, J., Leppin, C., Kotova, A., Reinke, S., Linnemann,
J., Maroun, F., & Magnussen, O. M. (2026). Role of Defects in Reversible Surface
Restructuring and Activity of Co3O4 Oxygen Evolution Electrocatalysts.
ACS Catalysis, Article acscatal.5c08785. https://doi.org/10.1021/acscatal.5c08785
bibtex: '@article{Scharf_Chandraraj_Dyk_Stebner_Lepin_Tian_El Bergmi Byaz_Stettner_Leppin_Kotova_et
al._2026, title={Role of Defects in Reversible Surface Restructuring and Activity
of Co3O4 Oxygen Evolution Electrocatalysts}, DOI={10.1021/acscatal.5c08785},
number={acscatal.5c08785}, journal={ACS Catalysis}, publisher={American Chemical
Society (ACS)}, author={Scharf, Carl Hendric and Chandraraj, Alex and Dyk, Konrad
and Stebner, Felix and Lepin, Sören and Tian, Jing and El Bergmi Byaz, Laila and
Stettner, Jochim and Leppin, Christian and Kotova, Anastasiia and et al.}, year={2026}
}'
chicago: Scharf, Carl Hendric, Alex Chandraraj, Konrad Dyk, Felix Stebner, Sören
Lepin, Jing Tian, Laila El Bergmi Byaz, et al. “Role of Defects in Reversible
Surface Restructuring and Activity of Co3O4 Oxygen Evolution
Electrocatalysts.” ACS Catalysis, 2026. https://doi.org/10.1021/acscatal.5c08785.
ieee: 'C. H. Scharf et al., “Role of Defects in Reversible Surface Restructuring
and Activity of Co3O4 Oxygen Evolution Electrocatalysts,”
ACS Catalysis, Art. no. acscatal.5c08785, 2026, doi: 10.1021/acscatal.5c08785.'
mla: Scharf, Carl Hendric, et al. “Role of Defects in Reversible Surface Restructuring
and Activity of Co3O4 Oxygen Evolution Electrocatalysts.”
ACS Catalysis, acscatal.5c08785, American Chemical Society (ACS), 2026,
doi:10.1021/acscatal.5c08785.
short: C.H. Scharf, A. Chandraraj, K. Dyk, F. Stebner, S. Lepin, J. Tian, L. El
Bergmi Byaz, J. Stettner, C. Leppin, A. Kotova, S. Reinke, J. Linnemann, F. Maroun,
O.M. Magnussen, ACS Catalysis (2026).
date_created: 2026-02-16T14:22:15Z
date_updated: 2026-02-16T14:25:00Z
department:
- _id: '985'
doi: 10.1021/acscatal.5c08785
keyword:
- electrocatalysis
- oxygen evolution reaction
- cobalt spinel
- operando characterization
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://pubs.acs.org/doi/10.1021/acscatal.5c08785
oa: '1'
publication: ACS Catalysis
publication_identifier:
issn:
- 2155-5435
- 2155-5435
publication_status: published
publisher: American Chemical Society (ACS)
quality_controlled: '1'
status: public
title: Role of Defects in Reversible Surface Restructuring and Activity of Co3O4
Oxygen Evolution Electrocatalysts
type: journal_article
user_id: '116779'
year: '2026'
...
---
_id: '61982'
abstract:
- lang: eng
text: Doped Co3O4 nanoparticles are investigated via spectro-electrochemistry in
the (pre-) oxygen evolution reaction (OER) regime by tracing the absorption signal
of the Co3+ d–d transition under applied bias for getting insight into the catalysts
activation and the formation of catalytically active phases. In the low potential
regime up to 1.37 VRHE, a rise in the optical absorption signal of the [Co3+]oct
d–d transition is observed and attributed to a structural change from [Co2+]tet
to [Co3+]oct due to an electrochemically induced surface restructuring with water.
For applied potentials higher than 1.37 VRHE an overall offset of the absorption
spectra in the UV–vis range, equivalent to a darkening of the materials is detected.
This is attributed to the formation of a CoOx(OH)y skin layer as supported by
high-energy X-ray diffraction (HE-XRD) measurements. We found that the kinetics
of the Co3+ states are heavily influenced by the type of dopant with V-doped Co3O4
exhibiting stable Co3+ states (>20 min) while the Mn-doped Co3O4 Co3+ states reduce
within 36 s under reductive bias. We conclude that doping Co3O4 with transition
metals affects the formation and potential-dependent thickness of the CoOx(OH)y
skin layer as the catalytically active phase and the formation of long-time stable
surface Co3+ states after activation in the first OER cycle.
article_type: original
author:
- first_name: L.
full_name: Kampermann, L.
last_name: Kampermann
- first_name: J.
full_name: Klein, J.
last_name: Klein
- first_name: T.
full_name: Wagner, T.
last_name: Wagner
- first_name: A.
full_name: Kotova, A.
last_name: Kotova
- first_name: C.
full_name: Placke-Yan, C.
last_name: Placke-Yan
- first_name: A.
full_name: Yasar, A.
last_name: Yasar
- first_name: L.
full_name: Jacobse, L.
last_name: Jacobse
- first_name: S.
full_name: Lasagna, S.
last_name: Lasagna
- first_name: Christian
full_name: Leppin, Christian
id: '117722'
last_name: Leppin
- first_name: S.
full_name: Schulz, S.
last_name: Schulz
- first_name: Julia
full_name: Linnemann, Julia
id: '116779'
last_name: Linnemann
orcid: 0000-0001-6883-5424
- first_name: A.
full_name: Bergmann, A.
last_name: Bergmann
- first_name: B.
full_name: Roldan Cuenya, B.
last_name: Roldan Cuenya
- first_name: G.
full_name: Bacher, G.
last_name: Bacher
citation:
ama: Kampermann L, Klein J, Wagner T, et al. Operando Analysis of the Pre-OER Activation
of Metal-Doped Co3O4 Nanoparticle Catalysts. ACS Catalysis.
2025;15(21):18391-18403. doi:10.1021/acscatal.5c03900
apa: Kampermann, L., Klein, J., Wagner, T., Kotova, A., Placke-Yan, C., Yasar, A.,
Jacobse, L., Lasagna, S., Leppin, C., Schulz, S., Linnemann, J., Bergmann, A.,
Roldan Cuenya, B., & Bacher, G. (2025). Operando Analysis of the Pre-OER Activation
of Metal-Doped Co3O4 Nanoparticle Catalysts. ACS Catalysis,
15(21), 18391–18403. https://doi.org/10.1021/acscatal.5c03900
bibtex: '@article{Kampermann_Klein_Wagner_Kotova_Placke-Yan_Yasar_Jacobse_Lasagna_Leppin_Schulz_et
al._2025, title={Operando Analysis of the Pre-OER Activation of Metal-Doped Co3O4
Nanoparticle Catalysts}, volume={15}, DOI={10.1021/acscatal.5c03900},
number={21}, journal={ACS Catalysis}, publisher={American Chemical Society (ACS)},
author={Kampermann, L. and Klein, J. and Wagner, T. and Kotova, A. and Placke-Yan,
C. and Yasar, A. and Jacobse, L. and Lasagna, S. and Leppin, Christian and Schulz,
S. and et al.}, year={2025}, pages={18391–18403} }'
chicago: 'Kampermann, L., J. Klein, T. Wagner, A. Kotova, C. Placke-Yan, A. Yasar,
L. Jacobse, et al. “Operando Analysis of the Pre-OER Activation of Metal-Doped
Co3O4 Nanoparticle Catalysts.” ACS Catalysis 15,
no. 21 (2025): 18391–403. https://doi.org/10.1021/acscatal.5c03900.'
ieee: 'L. Kampermann et al., “Operando Analysis of the Pre-OER Activation
of Metal-Doped Co3O4 Nanoparticle Catalysts,” ACS Catalysis,
vol. 15, no. 21, pp. 18391–18403, 2025, doi: 10.1021/acscatal.5c03900.'
mla: Kampermann, L., et al. “Operando Analysis of the Pre-OER Activation of Metal-Doped
Co3O4 Nanoparticle Catalysts.” ACS Catalysis, vol.
15, no. 21, American Chemical Society (ACS), 2025, pp. 18391–403, doi:10.1021/acscatal.5c03900.
short: L. Kampermann, J. Klein, T. Wagner, A. Kotova, C. Placke-Yan, A. Yasar, L.
Jacobse, S. Lasagna, C. Leppin, S. Schulz, J. Linnemann, A. Bergmann, B. Roldan
Cuenya, G. Bacher, ACS Catalysis 15 (2025) 18391–18403.
date_created: 2025-10-24T07:49:21Z
date_updated: 2025-12-07T17:15:53Z
department:
- _id: '985'
doi: 10.1021/acscatal.5c03900
intvolume: ' 15'
issue: '21'
keyword:
- electrocatalysis
- oxygen evolution reaction
- cobalt spinel
- operando characterization
- spectroelectrochemistry
language:
- iso: eng
page: 18391-18403
publication: ACS Catalysis
publication_identifier:
issn:
- 2155-5435
- 2155-5435
publication_status: published
publisher: American Chemical Society (ACS)
quality_controlled: '1'
status: public
title: Operando Analysis of the Pre-OER Activation of Metal-Doped Co3O4
Nanoparticle Catalysts
type: journal_article
user_id: '116779'
volume: 15
year: '2025'
...