Diffusion dynamics of water controlled by topology of potential energy surface inside carbon nanotubes

The effect of topology of single-walled carbon nanotubes (CNTs) on the diffusion dynamics of water confined in the armchair and zigzag CNTs was investigated. It was found that the activation energy of molecular diffusion in zigzag CNTs is greater than that in armchair ones at similar diameters, which leads to water molecules in zigzag CNT diffusing much slower than in armchair CNT. Further calculations of potential energy surfaces (PESs) of water in these two types of CNTs explain the mechanism of diffusion dynamics of confined water. This research shows that the topology of PESs inside CNT could control the diffusion behaviors of water inside it. Since topology of PESs inside CNT could be modified by various chemical and/or physical methods, this work indicates the possibility of controlling the diffusion behaviors inside the CNTs by molecular engineering approach, without changing its pore size.