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Oxygen Evolution on Mechanically Strained TiO 2/NiTi : Implications of Compositional Heterogeneity at (Photo)electrocatalytic Interfaces.

Carvalho, O Quinn ; Dutta, Nikita S ; Ghoshal, Debjit ; Harvey, Steven P ; Kerner, Ross A ; Li, Shuya ; Schichtl, Zebulon G ; Walker, Patrick ; Wilder, Logan M and Girotto, Gustavo Z LU orcid , et al. (2025) In ACS electrochemistry 1(10). p.2177-2189
Abstract

The adsorption and activation energetics underpinning small molecule conversion on heterogeneous (photo)-electrocatalysts are intrinsically tied to catalyst surface properties. Absent compositional characterization techniques with sufficient interface sensitivity, however, (photo)-electrochemical performance can be misinterpreted in the context of bulk or near-surface material properties. Here we provide a fundamental investigation of the convoluting role of near-surface compositional heterogeneity in the interpretation of (photo)-electrochemical alkaline oxygen evolution reaction (OER) activity, highlighting challenges in correlating composition measured by surface- and near-surface-sensitive probes. TiO
2 thin films grown by... (More)

The adsorption and activation energetics underpinning small molecule conversion on heterogeneous (photo)-electrocatalysts are intrinsically tied to catalyst surface properties. Absent compositional characterization techniques with sufficient interface sensitivity, however, (photo)-electrochemical performance can be misinterpreted in the context of bulk or near-surface material properties. Here we provide a fundamental investigation of the convoluting role of near-surface compositional heterogeneity in the interpretation of (photo)-electrochemical alkaline oxygen evolution reaction (OER) activity, highlighting challenges in correlating composition measured by surface- and near-surface-sensitive probes. TiO
2 thin films grown by air-annealing the superelastic alloy Nitinol (TiO
2/NiTi) crack under tensile mechanical strain, increasing the number of electrochemically active Ni sites (Ni site density) that are probed via voltammetric features corresponding to Ni
3+/Ni
2+ redox events. (Photo)-electrochemical OER kinetics trend with Ni site density, with overpotentials and Tafel slopes decreasing for Ni site densities < 10
13 Ni/cm
2
geo and asymptotically approaching the performance of the base NiTi substrate for Ni site densities > 10
13 Ni/cm
2
geo. Photoelectrochemical fill factors follow similar Ni site density dependent trends. When probing unstrained TiO
2/NiTi, Ni site densities are two orders of magnitude higher when comparing near-surface-sensitive techniques (e.g., X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (TOF-SIMS), and scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS)) to surface-sensitive electrochemical measurements. This result highlights the challenge of correlating kinetic performance with intrinsic surface properties of electrochemical interfaces in the presence of near-surface compositional heterogeneity. Further, it reinforces the importance of fundamental investigations of surfaces with well-controlled composition and structure and the need for physically grounded and self-consistent interpretation of multiple near-surface characterization techniques.

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publishing date
type
Contribution to journal
publication status
published
in
ACS electrochemistry
volume
1
issue
10
pages
13 pages
external identifiers
  • pmid:41058914
ISSN
2997-0571
DOI
10.1021/acselectrochem.5c00228
language
English
LU publication?
no
additional info
© 2025 The Authors. Published by American Chemical Society.
id
732ffa94-d6a4-449d-9d22-bccbb64779e6
date added to LUP
2025-10-10 12:46:42
date last changed
2025-10-16 11:26:49
@article{732ffa94-d6a4-449d-9d22-bccbb64779e6,
  abstract     = {{<p>The adsorption and activation energetics underpinning small molecule conversion on heterogeneous (photo)-electrocatalysts are intrinsically tied to catalyst surface properties. Absent compositional characterization techniques with sufficient interface sensitivity, however, (photo)-electrochemical performance can be misinterpreted in the context of bulk or near-surface material properties. Here we provide a fundamental investigation of the convoluting role of near-surface compositional heterogeneity in the interpretation of (photo)-electrochemical alkaline oxygen evolution reaction (OER) activity, highlighting challenges in correlating composition measured by surface- and near-surface-sensitive probes. TiO<br>
 2 thin films grown by air-annealing the superelastic alloy Nitinol (TiO<br>
 2/NiTi) crack under tensile mechanical strain, increasing the number of electrochemically active Ni sites (Ni site density) that are probed via voltammetric features corresponding to Ni<br>
 3+/Ni<br>
 2+ redox events. (Photo)-electrochemical OER kinetics trend with Ni site density, with overpotentials and Tafel slopes decreasing for Ni site densities &lt; 10 <br>
 13 Ni/cm<br>
 2 <br>
 geo and asymptotically approaching the performance of the base NiTi substrate for Ni site densities &gt; 10 <br>
 13 Ni/cm<br>
 2 <br>
 geo. Photoelectrochemical fill factors follow similar Ni site density dependent trends. When probing unstrained TiO<br>
 2/NiTi, Ni site densities are two orders of magnitude higher when comparing near-surface-sensitive techniques (e.g., X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (TOF-SIMS), and scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS)) to surface-sensitive electrochemical measurements. This result highlights the challenge of correlating kinetic performance with intrinsic surface properties of electrochemical interfaces in the presence of near-surface compositional heterogeneity. Further, it reinforces the importance of fundamental investigations of surfaces with well-controlled composition and structure and the need for physically grounded and self-consistent interpretation of multiple near-surface characterization techniques.<br>
 </p>}},
  author       = {{Carvalho, O Quinn and Dutta, Nikita S and Ghoshal, Debjit and Harvey, Steven P and Kerner, Ross A and Li, Shuya and Schichtl, Zebulon G and Walker, Patrick and Wilder, Logan M and Girotto, Gustavo Z and Jaugstetter, Maximilian and Nemsak, Slavomir and Crumlin, Ethan J and Miller, Elisa M and Greenaway, Ann L}},
  issn         = {{2997-0571}},
  language     = {{eng}},
  month        = {{10}},
  number       = {{10}},
  pages        = {{2177--2189}},
  series       = {{ACS electrochemistry}},
  title        = {{Oxygen Evolution on Mechanically Strained TiO
        2/NiTi : Implications of Compositional Heterogeneity at (Photo)electrocatalytic Interfaces.}},
  url          = {{http://dx.doi.org/10.1021/acselectrochem.5c00228}},
  doi          = {{10.1021/acselectrochem.5c00228}},
  volume       = {{1}},
  year         = {{2025}},
}