jz7b01573_si_002.avi (21.16 MB)
Coexistence of Physisorbed and Solvated HCl at Warm Ice Surfaces
media
posted on 2017-09-13, 00:00 authored by Xiangrui Kong, Astrid Waldner, Fabrizio Orlando, Luca Artiglia, Thomas Huthwelker, Markus Ammann, Thorsten Bartels-RauschThe
interfacial ionization of strong acids is an essential factor
of multiphase and heterogeneous chemistry in environmental science,
cryospheric science, catalysis research and material science. Using
near ambient pressure core level X-ray photoelectron spectroscopy,
we directly detected a low surface coverage of adsorbed HCl at 253
K in both molecular and dissociated states. Depth profiles derived
from XPS data indicate the results as physisorbed molecular HCl at
the outermost ice surface and dissociation occurring upon solvation
deeper in the interfacial region. Complementary X-ray absorption measurements
confirm that the presence of Cl– ions induces significant
changes to the hydrogen bonding network in the interfacial region.
This study gives clear evidence for nonuniformity across the air–ice
interface and questions the use of acid–base concepts in interfacial
processes.