Hydration behavior and dynamics of water molecules in graphite oxide

In contrast to graphite intercalation compounds, graphite oxide (GO) is hydrophilic. However, the information about the mobility of the water molecules is still sparse. We show in this report that the degree of hydration and the kinetics of water uptake depend crucially on the preparation and aging conditions. The best sample we have ever got shows layer distances of 8, 9 and 11.5 A at relative humidities of 45, 75 and 100%, respectively. With time-of-flight (TOF) neutron scattering (V3/NEAT spectrometer) diffusion processes for rotation and translation have been investigated in the temperature range 220-320 K with an energy resolution of 93 mu eV. Quasi-elastic scattering was observed for all temperatures. Three types of motion can be sorted out. The first one is a translational motion of water molecules in pores between the GO particles for samples equilibrated at 100% relative humidity. Samples equilibrated at 45 and 75% relative humidity do not show this type of water. They exhibit two types of localized motions with different activation energies. We try to assign one type of these motions to confined water molecules encapsulated in the interlayer space between the functional groups attached to the carbon grid. (c) 2006 Elsevier Ltd. All rights reserved.