▎ 摘　　要

The interaction of water with nanostructured, functional carbon materials has led to fascinating phenomena, such as electricity induced by water evaporation from carbon black sheets from water evaporation. Here, we carry out a comprehensive ab initio study of the interaction of charge-neutral and protonated water molecules with graphene oxides with focus on typical epoxide, carbonyl, hydroxyl, and carboxyl groups in carbon black sheets. These oxygen groups can greatly enhance both the binding energy and the charge transfer between water and graphene. Among the groups, the carboxyl group on graphene is most attractive to a water molecule and drives a transfer of 0.024 e to graphene due to the formation of two hydrogen bonds between them, in contrast to an inverse transfer of 0.01 e from pristine graphene. Protonation of water molecules can be leveraged to further upgrade the water-graphene interaction, independent of the functional groups. A distinctly stable (H2O)(3)H+ cluster is identified and found to be located at a deeper minimum upon interaction with the carboxyl group on graphene. Surprisingly, each (H2O)(3)H+ cluster can draw 0.084 e from pristine graphene and up to 0.128 e from graphene with a carboxyl group, attributed to large differences in work functions between the protonated clusters and the functionalized graphene. These results reveal the synergistic effect of oxygen functional groups and protonation in tuning charge exchange between water and graphene and deepen the understanding of hydrovoltaic effects.