A Photoemission Study of Solute−Solvent Interaction:  Coadsorption of Na and H₂O on WSe₂(0001)

Abstract

Semiconductor/electrolyte model interfaces are prepared in UHV by adsorbing and coadsorbing the electrolyte species Na and H2O onto chemically inert van der Waals (0001) surfaces of WSe2 at low temperatures (100K). The state of the adsorbed species is monitored by soft X-ray photoelectron spectroscopy (SXPS) and the surface potentials, i.e., band bending eV bb, surface photovoltage SPV, electron affinity χ, and work function Φ by SXPS and ultraviolet photoelectron spectroscopy (UPS). H2O coadsorbed to metallic Na clusters is dissociated and electron emission lines due to Na+ and OH- ions are observed. Coadsorption of Na to condensed ice layers preserves the H2O molecules. The 3s electrons of the adsorbed Na atoms are transferred to the p-WSe2 substrate as indicated by a depletion space charge layer on p-WSe2. With increasing exposition to SX radiation, the 2p emission of the Na+ ions is stepwise shifted to lower binding energy. We relate this successive shift to an increasing number of reorganized H2O molecules from the adsorbate layer in its ice configuration to the hydration shell of Na+.

Effect of Sodium on HCl Hydrate Diffusion in Ice: Evidence for Anion−Cation Trapping

“…Sodium could ionize in ice by forming a solvated electron via Na + n H 2 O → Na + + e - (H 2 O) n . This ionization process is supported by numerous experimental − and theoretical , studies. Sodium could also undergo ionization by reacting with H 2 O to produce H 2 : Na + H 2 O → Na + + OH - + 1 / 2 H 2 . , …”

Water Interaction with Sputter-Deposited Nickel Oxide on n-Si Photoanode: Cryo Photoelectron Spectroscopy on Adsorbed Water in the Frozen Electrolyte Approach

“…The latter one is typical for interacting H 2 O molecules in a multilayer film. [31][32][33][34][35] However, up to a water exposure of 1.6 L, the species at 532.7 eV is dominant and only for 10 L, the species at 533.5 eV becomes predominant. As in the UP spectra below the fingerprint of molecular water is observed at low water exposure, we assign the first species at 532.7 eV to a H 2 O-NiO surface species, physisorbed onto stoichiometric nickel oxide.…”

Synchrotron Photoemission Spectroscopy Study of p-GaInP2(100) Electrodes Emersed from Aqueous HCl Solution under Cathodic Conditions

“…However, ultrahigh vacuum (UHV) is required, which is not compatible with the liquid contacts. In the past, a number of approaches have already been suggested for the study of semiconductor/electrolyte interfaces using photoemission spectroscopy, e.g., freezing-in a thin electrolyte layer on the semiconductor surface, as well as step-by-step coadsorption of electrolyte components onto cooled sample surfaces. , Also the application of near-ambient pressure X-ray photoelectron spectroscopy (NP-XPS) , can enable the detailed study of water interaction with semiconductor surfaces at different temperatures. First experiments using operando ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), as well as in situ electrochemical X-ray photoelectron spectroscopy, have been performed to analyze semiconductor/liquid junctions at room temperature under real-time electrochemical control.…”