Surface Reactions of Carbon Dioxide at the Adsorbed Water−Oxide Interface

Abstract

In this study, FTIR spectroscopy is used to investigate surface reactions of carbon dioxide at the adsorbed water−oxide interface. In particular, FTIR spectra following CO2 adsorption in the presence and absence of coadsorbed water on hydroxylated nanoparticulate Fe2O3 and γ-Al2O3 at 296 K are reported. In the absence of coadsorbed water, CO2 reacts with surface O−H groups to form adsorbed bicarbonate on the surface. In the presence of coadsorbed water, this reaction is blocked as water hydrogen bonds to the reactive M−OH sites. Instead, CO2 reacts with adsorbed water to yield adsorbed carbonate and protonated surface hydroxyl groups, M−OH2 +, through a proposed carbonic acid intermediate. The carbonate spectra recorded between 10 and 90% RH are nearly identical to that of carbonate adsorbed on these surfaces in the presence of the liquid water. FTIR isotope studies show that there is extensive exchange between oxygen in adsorbed water and oxygen atoms in both adsorbed carbonate and gas-phase carbon dioxide. On the basis of these experimental results along with quantum chemical calculations, a mechanism is proposed for surface reactions of carbon dioxide at the adsorbed water−oxide interface.

Ferrihydrite reactivity toward carbon dioxide

“…More recently Baltrusaitis et el. showed a similar behavior for CO 2 on nano-hematite surfaces under varying humidity [49]. Infrared spectra presented by Baltrusaitis in the region of 1700-1200 cm À1 under dry conditions (<3% RH) are similar to those presented in this work.…”

“…With regard to the mechanistic details concerning the formation of carbonate and bicarbonate on ferrihydrite it is useful to draw relevant information from prior studies that have investigated the interaction of CO 2 with related materials such as goethite a-FeO(OH) [41,45,46,48] and hematite a-Fe 2 O 3 [1,28,49]. Recently, Bargar et al.…”

Perspective: Water cluster mediated atmospheric chemistry

“…190 Adsorbed water on surfaces of oxide and mineral dust aerosols were characterized in insightful experiments by Grassian et al and shown to alter and enhance reactivity of O 3 , H 2 CO 3 and HNO 3 . [191][192][193][194][195] These and other examples clearly point to enhanced reactivity on aqueous surfaces and to the success of studying complex environments with cluster models.…”

Local structural order in carbonic acid polymorphs: Raman and FT‐IR spectroscopy

“…As a surface‐adsorbed species, carbonic acid was also identified on carbonate minerals in acidic but dry atmosphere44–46 and is a possible surface intermediate in the process of CO 2 adsorption on hydroxylated oxides, e.g. Fe 2 O 3 or Al 2 O 3 47, 48…”