X‐Ray Absorption Spectroscopy of TiO 2 Nanoparticles in Water Using a Holey Membrane‐Based Flow Cell

Many applications of TiO 2 nanoparticles, such as photocatalytic water splitting or water remediation, occur in aqueous environment. However, the impact of solvation on TiO 2 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 TiO 2 materials, but so far only in vacuum conditions. Here, oxygen K edge and titanium L edge X‐ray absorption spectroscopy characterization of TiO 2 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.