September 6, 2018
Journal Article

Water Structure Controls Carbonic Acid Formation in Adsorbed Water Films


Reaction pathways and kinetics in highly structured H2O adsorbed as Ångstroms to nanometers thick layers on mineral surfaces are distinct from those facilitated by bulk liquid water. We investigate the role of interfacial H2O structure in the reaction of H2O and CO2 to form carbonic acid (H2CO3) in thin H2O films condensed onto silica nanoparticles from humidified supercritical CO2. Rates of carbonic acid formation are correlated to spectroscopic signatures of H2O structure using oxygen isotopic tracers and infrared spectroscopy. While carbonic acid virtually does not form in the supercritical phase, the silica surface catalyzes this reaction by concentrating H2O through adsorption at hydrophilic silanol groups. Within measurement uncertainty, we found no evidence that carbonic acid forms when exclusively ice-like structured H2O is detected at the silica surface. Instead, formation of H2C18O16O2 from H218O and C16O2 was found to be linearly correlated with liquid-like structured H2O that formed on the ice-like layer.

Revised: February 20, 2020 | Published: September 6, 2018


Miller Q., E.S. Ilton, O. Qafoku, D.A. Dixon, M. Vasiliu, C.J. Thompson, and H.T. Schaef, et al. 2018. Water Structure Controls Carbonic Acid Formation in Adsorbed Water Films. The Journal of Physical Chemistry Letters 9, no. 17:4988–4994. PNNL-SA-136469. doi:10.1021/acs.jpclett.8b02162