Beyond nitrogen: an oxygen-chemical-potential framework for defect-engineered TiO₂ nanotube architectures in energy conversion and environmental catalysis.
4 affiliations
- 1University of Tabriz Tabriz Iran.
- 2Karshi State Technical University Karshi Uzbekistan.
- 3National University of Uzbekistan Named After Mirzo Ulugbek Tashkent Uzbekistan.
- 4S.A. Azimov Physical-Technical Institute of Uzbekistan Academy of Sciences Tashkent Uzbekistan [email protected] [email protected].
Abstract
Nitrogen-doped titanium dioxide (TiO2) nanotube arrays (N-TNTs) have become a reference platform for solar energy conversion and electrochemical storage, yet the field remains organised around a material-centric narrative in which nitrogen is treated as the primary functional agent and each application is optimised in isolation. Here we argue for a different reading. Drawing together evidence from lithium-ion storage, supercapacitive charge storage, photoelectrochemical water splitting and visible-light photocatalysis, we show that the performance-determining quantity in these systems is not the nitrogen content itself but the coupled population of shallow oxygen vacancies (Vo) and Ti3+ centres-a single defect state whose equilibrium is set, during synthesis and post-treatment, by the oxygen chemical potential (µo). In this view nitrogen acts chiefly as a thermodynamic stabiliser that pins this defect state and shifts its formation window, rather than as an independent visible-light 'switch'. Re-examining the literature through this lens reveals that the four applications are not separate optimisation problems but different projections of the same underlying defect equilibrium, and that their apparently disparate optimal conditions collapse onto a common design window in the µo-defect-density plane. We formalise this as a defect-state design map, propose a compact and transferable defect-state descriptor together with a minimum defect-reporting protocol to make results comparable across laboratories, and outline how operando defect metrology and closed-loop, machine-learning-guided synthesis can convert empirical doping into predictive defect-equilibrium engineering. This reframing offers a unifying and testable basis for designing N-TNT architectures-and, more broadly, defective oxide nanomaterials-for robust, scalable energy and environmental devices.
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BibTeX
@article{ghazaie2026beyond,
title = {{Beyond nitrogen: an oxygen-chemical-potential framework for defect-engineered TiO₂ nanotube architectures in energy conversion and environmental catalysis.}},
author = {Hakimeh Ghazaie and Shahab Khameneh Asl and Shahin Khameneh Asl and Nurbek Rakhimov and Shohruh Sayfulloev and Sardorbek Saydaliev and Alisher Kahramonov and Utkirjon Sharopov},
journal = {Nanoscale advances},
year = {2026},
month = oct,
doi = {10.1039/d6na00756b},
url = {https://europepmc.org/article/MED/42953807},
note = {CC BY},
}
RIS
TY - JOUR
TI - Beyond nitrogen: an oxygen-chemical-potential framework for defect-engineered TiO₂ nanotube architectures in energy conversion and environmental catalysis.
AU - Hakimeh Ghazaie
AU - Shahab Khameneh Asl
AU - Shahin Khameneh Asl
AU - Nurbek Rakhimov
AU - Shohruh Sayfulloev
AU - Sardorbek Saydaliev
AU - Alisher Kahramonov
AU - Utkirjon Sharopov
PY - 2026
DA - 2026/10/23
JO - Nanoscale advances
DO - 10.1039/d6na00756b
UR - https://europepmc.org/article/MED/42953807
AB - Nitrogen-doped titanium dioxide (TiO2) nanotube arrays (N-TNTs) have become a reference platform for solar energy conversion and electrochemical storage, yet the field remains organised around a material-centric narrative in which nitrogen is treated as the primary functional agent and each application is optimised in isolation. Here we argue for a different reading. Drawing together evidence from lithium-ion storage, supercapacitive charge storage, photoelectrochemical water splitting and visible-light photocatalysis, we show that the performance-determining quantity in these systems is not the nitrogen content itself but the coupled population of shallow oxygen vacancies (Vo) and Ti3+ centres-a single defect state whose equilibrium is set, during synthesis and post-treatment, by the oxygen chemical potential (µo). In this view nitrogen acts chiefly as a thermodynamic stabiliser that pins this defect state and shifts its formation window, rather than as an independent visible-light 'switch'. Re-examining the literature through this lens reveals that the four applications are not separate optimisation problems but different projections of the same underlying defect equilibrium, and that their apparently disparate optimal conditions collapse onto a common design window in the µo-defect-density plane. We formalise this as a defect-state design map, propose a compact and transferable defect-state descriptor together with a minimum defect-reporting protocol to make results comparable across laboratories, and outline how operando defect metrology and closed-loop, machine-learning-guided synthesis can convert empirical doping into predictive defect-equilibrium engineering. This reframing offers a unifying and testable basis for designing N-TNT architectures-and, more broadly, defective oxide nanomaterials-for robust, scalable energy and environmental devices.
SN - 2516-0230
ER -