X‐Ray Absorption Spectroscopy of TiO₂ Nanoparticles in Water Using a Holey Membrane‐Based Flow Cell

Abstract Many applications of TiO₂ nanoparticles, such as photocatalytic water splitting or water remediation, occur in aqueous environment. However, the impact of solvation on TiO₂ electronic structure remains unclear because only few experimental methods are currently available to probe nanoparticle–water interface. Soft X‐ray absorption spectroscopy has been extensively used to characterize the electronic structure of TiO₂ materials, but so far only in vacuum conditions. Here, oxygen K edge and titanium L edge X‐ray absorption spectroscopy characterization of TiO₂ nanoparticles measured directly in aqueous dispersion is presented. For this purpose, a new method to probe nanomaterials in liquid using a holey membrane‐based flow cell is introduced. With this approach, the X‐ray transmission of the membrane is increased, especially in the water window, compared to solid membranes.