Predictive Removal of Interfacial Defect-Induced Trap States between Titanium Dioxide Nanoparticles via Sub-Monolayer Zirconium Coating

Joyashish Debgupta; Leonardo Lari; Mark Isaacs; John Carey; Keith P McKenna; Vlado K Lazarov; Victor Chechik; Richard E Douthwaite

doi:10.1021/acs.jpcc.2c06927

Predictive Removal of Interfacial Defect-Induced Trap States between Titanium Dioxide Nanoparticles via Sub-Monolayer Zirconium Coating

J Phys Chem C Nanomater Interfaces. 2022 Dec 23;127(1):660-671. doi: 10.1021/acs.jpcc.2c06927. eCollection 2023 Jan 12.

Authors

Joyashish Debgupta¹, Leonardo Lari², Mark Isaacs^{3

4}, John Carey², Keith P McKenna², Vlado K Lazarov², Victor Chechik¹, Richard E Douthwaite¹

Affiliations

¹ Department of Chemistry, University of York, York YO10 5DD, UK.
² Department of Physics, University of York, Heslington, York YO10 5DD, UK.
³ HarwellXPS, R92 Research Complex at Harwell, Rutherford Appleton Laboratories, Harwell, Didcot OX11 0QS, UK.
⁴ Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.

Abstract

First principles modeling of anatase TiO₂ surfaces and their interfacial contacts shows that defect-induced trap states within the band gap arise from intrinsic structural distortions, and these can be corrected by modification with Zr(IV) ions. Experimental testing of these predictions has been undertaken using anatase nanocrystals modified with a range of Zr precursors and characterized using structural and spectroscopic methods. Continuous-wave electron paramagnetic resonance (EPR) spectroscopy revealed that under illumination, nanoparticle-nanoparticle interfacial hole trap states dominate, which are significantly reduced after optimizing the Zr doping. Fabrication of nanoporous films of these materials and charge injection using electrochemical methods shows that Zr doping also leads to improved electron conductivity and mobility in these nanocrystalline systems. The simple methodology described here to reduce the concentration of interfacial defects may have wider application to improving the efficiency of systems incorporating metal oxide powders and films including photocatalysts, photovoltaics, fuel cells, and related energy applications.