The Metal-Oxide Nanoparticle-Aqueous Solution Interface Studied by Liquid-Microjet Photoemission
Hebatallah Ali1, Bernd Winter2, Robert Seidel3,4
1Physics Department, Women Faculty for Art, Science and Education, Ain Shams University, Heliopolis, Cairo 11757, Egypt.
Accounts of Chemical Research
|June 13, 2023
Summary
Soft X-ray photoelectron spectroscopy with liquid microjets reveals how water interacts with transition-metal oxide nanoparticles. This technique distinguishes adsorbed water from bulk water, identifying hydroxyl species and detailing surface interactions crucial for catalysis.
Area of Science:
- Surface Science
- Materials Chemistry
- Spectroscopy
- Nanotechnology
Background:
- Liquid-microjet soft X-ray photoelectron spectroscopy (PES) is a powerful tool for studying liquid electronic structures.
- Investigating nanoparticle-water interfaces is crucial for applications like (photo)electrocatalysis.
- Traditional PES methods face challenges with the short photoelectron mean free path in solution.
Purpose of the Study:
- To investigate the interaction of water molecules with transition-metal oxide (TMO) nanoparticle surfaces in aqueous solutions.
- To identify interfacial species and understand water adsorption mechanisms at the nanoparticle-electrolyte interface.
- To explore the potential of TMO nanoparticles for (photo)electrocatalytic applications.
Main Methods:
- Liquid-microjet soft X-ray photoelectron spectroscopy (PES) was employed.
- Experiments were conducted on hematite (α-Fe2O3) and anatase (TiO2) nanoparticles dispersed in aqueous solutions.
- Resonant photoemission and partial electron yield X-ray absorption (PEY-XA) spectra were utilized for detailed analysis.
Main Results:
- PES successfully distinguished between bulk water and water adsorbed on TMO nanoparticle surfaces.
- Hydroxyl species resulting from dissociative water adsorption were identified.
- Water adsorption was found to be dissociative on hematite and molecular on TiO2 at low pH, becoming dissociative on TiO2 at near-basic pH.
Conclusions:
- The liquid-microjet PES technique provides unique insights into the solid-electrolyte interface at the nanoparticle level.
- The study elucidates the distinct water-TMO surface interactions as a function of pH, crucial for understanding catalytic processes.
- Resonance processes in PES can provide information on charge transfer and electron delocalization at the interface.
