On the Importance of Nanoparticle Necks and Carbon Impurities for Charge Trapping in TiO2

Michael J Elser, Ellie Neige, Thomas Berger, Mario Chiesa, Elio Giamello, Keith McKenna*, Thomas Risse, Oliver Diwald*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Particle attachment and neck formation inside TiO 2 nanoparticle networks determine materials performance in sensing, photo-electrochemistry, and catalysis. Nanoparticle necks can feature point defects with potential impact on the separation and recombination of photogenerated charges. Here, we investigated with electron paramagnetic resonance a point defect that traps electrons and predominantly forms in aggregated TiO 2 nanoparticle systems. The associated paramagnetic center resonates in the g factor range between g = 2.0018 and 2.0028. Structure characterization and electron paramagnetic resonance data suggest that during materials processing, the paramagnetic electron center accumulates in the region of nanoparticle necks, where O 2 adsorption and condensation can occur at cryogenic temperatures. Complementary density functional theory calculations reveal that residual carbon atoms, which potentially originate from synthesis, can substitute oxygen ions in the anionic sublattice, where they trap one or two electrons that mainly localize at the carbon. Their emergence upon particle neck formation is explained by the synthesis- and/or processing-induced particle attachment and aggregation facilitating carbon atom incorporation into the lattice. This study represents a substantial advance in linking dopants, point defects, and their spectroscopic fingerprints to microstructural features of oxide nanomaterials.

Original languageEnglish
Pages (from-to)8778-8787
Number of pages10
JournalJournal of Physical Chemistry C
Volume127
Issue number18
Early online date3 May 2023
DOIs
Publication statusPublished - 11 May 2023

Bibliographical note

© 2023 The Authors. Published by American Chemical Society.

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