Adsorption of water molecules on partially oxidized graphite surfaces: a molecular dynamics study of the competition between OH and COOH sites.

In this paper, molecular dynamic simulations are used to study the adsorption of water molecules on partially oxidized graphite surfaces containing COOH and OH sites. More specially, the competition between the OH and COOH sites with respect to water adsorption is characterized at three different temperatures (200, 250 and 300 K). The simulations show a strong preferential clustering of the water molecules around the COOH sites irrespective of the temperature. The present results also show that the OH sites can influence the water adsorption process at high temperature, if their local density on the surface is sufficiently large. In this situation, the dynamics of the adsorption process is shown to depend on the distribution of these OH sites on the surface. These results give insights into the water adsorption mechanisms on oxidized graphite surfaces constituting, for example, black carbons or soot particles emitted by aircraft.