Interaction of Carbon Dioxide and Hydroxide Ion at the Surface of Ice Films

Abstract

We studied the interactions of CO2 with ice films prepared in either a neutral or basic condition, with emphasis on the examination of feasibility for the reaction between CO2 and hydroxide ion present at the ice surfaces. To this end, Cs+ reactive ion scattering (RIS) and low-energy sputtering (LES) techniques were used to scrutinize the chemical species present at the surfaces, in conjunction with temperature-programmed desorption (TPD) to monitor the desorbing species. Ice films were grown in a nonporous amorphous phase or a crystalline phase. Excess hydroxide ions were added onto the ice film surfaces by the hydrolysis of Na atoms. TPD experiments showed that CO2 molecules desorbed from the ice film surfaces before the onset of water sublimation near 140 K, regardless of the presence or absence of excess hydroxide ions. CO2 adsorption did not produce CO2−water complexes nor hydrolysis products on both film surfaces in the temperature range 80−180 K. The nonreactivity of CO2 toward hydroxide ion at the...