Aqueous carbonic acid(H2CO3) is the centerpiece of both the global carbon cycle and physiological buffer systems, yet it remains poorly characterized despite enormous effort. This reflects the fact that carbonic acid is intrinsically unstable upon contact with even a single water molecule, reacting in via a proton chain mechanism to ultimately form aqueous bicarbonate and carbonate anions and hydrated protons, which comprises the reversible mechanism of dissolution of CO2 gas. While solid and gaseous carbonic acid have been studied in some detail, only two spectroscopic studies of the aqueous form have been successful. We report the detection and characterization of both aqueous H2CO3 and dissolved CO2 by X-ray absorption spectroscopy in a liquid microjet designed to effect rapid mixing of reactant solutions, wherein protonation of a bicarbonate solution continuously generates the short-lived acid under ambient conditions. Accompanying first principles calculations of the carbon K-edge transitions facilitate spectral assignment and interpretation. Lam, R. K., England, A. H., Smith, J. W., Rizzuto, A. M., Shih, O., Prendergast, D., Saykally, R. J., "The hydration structure of dissolved carbon dioxide from X-ray absorption spectroscopy" Chem. Phys. Lett., 633, 214-217 (2015). Lam, R. K., England, A. H., Sheardy, A. T., Shih, O., Smith, J. W., Rizzuto, A. M., Prendergast, D., Saykally, R. J., "The hydration structure of aqueous carbonic acid from X-ray absorption spectroscopy" Chem. Phys. Lett., 614, 282-286 (2014) *Cover Article. *A. H. England, A. M. Duffin, C. P. Schwartz, J. S. Uejio, D. Prendergast, and R. J. Saykally "On the Hydration and Hydrolysis of Carbon Dioxide," Chem. Phys. Lett. 514, 187-195 (2011)*Cover Article

Hydration structure of aqueous carbonic acid and carbon dioxide from x-ray absorption spectroscopy

251st National Meeting (2016)

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