A Combination of EPR, Microscopy, Electrophoresis and Theory to Elucidate the Chemistry of W- and N-Doped TiO2 Nanoparticle/Water Interface

Sam Gorman, Kirstie Rickaby, Li Lu, Christopher J. Kiely, Donald Macphee, Andrea Folli* (Corresponding Author)

*Corresponding author for this work

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The doping of TiO2-based nanomaterials for semiconductor-sensitised photoreactions has been a practice extensively studied and applied for many years. The main goal remains the improvement of light harvesting capabilities under passive solar irradiation, that in the case of undoped TiO2 is limited and restricted to relatively low latitudes. The activity and selectivity of doped TiO2 photocatalysts are generally discussed on the basis of the modified band structure; energetics of intrinsic or extrinsic band gaps including trapping states; redox potentials of band edges, including band bending at solid/fluid interfaces; and charge carriers scavenging/transfer by/to adsorbed species. Electron (and hole) transfer to adsorbates is often invoked to justify the formation of highly reactive species (e.g., HO. from water); however, a complete description of the nanoparticle surface chemistry dictating adsorption/desorption events is often missing or overlooked. Here, we show that by employing a surface electrochemical triple-layer (TLM) approach for the nanoparticles/water interface, in combination with electron paramagnetic resonance spectroscopy (EPR), transmission electron microscopy and electrophoretic measurements, we can elucidate the surface chemistry of doped TiO2 nanoparticles and link it to the nature of the dopants. Exemplifying it for the cases of undoped, as well as W- and N-doped and codoped TiO2 nanoparticles, we show how surface charge density; surface, Stern and ζ potentials; surface acidity constants; and speciation of surface sites are influenced by the nature of the dopants and their loading.
Original languageEnglish
Article number1305
Number of pages20
Issue number11
Early online date28 Oct 2021
Publication statusPublished - 1 Nov 2021

Bibliographical note

Funding: The authors thank the European Commission (FP7-ENV-2011-ECO-INNO-TwoStage 283062) for funding. C.J.K. gratefully acknowledges funding from the National Science Foundation Major Research Instrumentation program
(GR# MRI/DMR-1040229).


  • Electron paramagnetic resonance
  • semiconductor photocatalysis
  • TiO2
  • colloidal chemistry
  • solid-liquid interface
  • metal oxides
  • surface chemistry
  • surface charge density
  • zeta potential
  • isoelectric point
  • pH of zero charge


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