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Molecular Foundry

HIGHLIGHTSWater is ice-like at TiO2-aqueous solution interfaces
October 21, 2021

Scientific Achievement

Top left: Schematic of the cell design. X-rays penetrate into the solution through a 100nm SiNx support coated with a 6.6 nm of TiO2 film on 10 nm of Au. Electrons emitted from the decay of O K-level holes report the density of unoccupied states in TiO2 and LUMO levels of interfacial water. Right: NEXAFS of: a) TiO2 in vacuum; b) TiO2 + water in the cell. The difference spectrum (a-b) shows the contribution of the water next to the TiO2-water interface. The spectrum is nearly identical to that of ice (red curve).

Demonstrated that the first few (~4) layers of water at the TiO2-water interface are structured like ice, a finding that helps understand ionic distribution, ion insertion, and solvation phenomena in oxide materials

Significance and Impact

Advancing the understanding of the molecular structure of aqueous solid-liquid (S-L) interfaces is key to improve & control corrosion, desalination, and electrochemical reactions, where ions have to diffuse though solvent layers near interfaces

Research Details

  • Near Edge X-Ray Absorption spectroscopy was used in the electron-yield mode collected at the sample electrode. The short mean free path of the electrons ensures a spatial resolution of few nm
  • The O K-edge spectra of the TiO2 film (6.6 nm) acting as the working electrode and that of nearby water reveal the ice-like structure of the first few water layers
    Van Spronsen, M.; Zhao, X.; Jaugstetter, M.; Escudero, C.; Duchoň, T.; Hunt, A.; Waluyo, I.; Yang, P.; Tschulik, K.; Salmeron, M., J. Phys. Chem. Lett. 2021, 12, 10212−10217, DOI: 10.1021/acs.jpclett.1c02115

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