where H(ξ) is the configuration part of a parametrized Hamiltonian and ξ is a coupling parameter that characterises the strength of Coulomb interactions between sulphate groups i and j. Like Nafion , ΔA/(NPkBT) is the difference in the excess Helmholtz free energy per sulphate where NP is the total number of protons, kB is the Boltzmann constant and T is temperature. The irreversible electric-field-induced Graphenion morphology inspires the first learning outcome: if an applied electric field induces microscopic changes in the morphology of a 3DSGO membrane, then the changes remain after the removal of the electric field. By conceiving that H2O molecules and H3O + ions form part of the same cluster for a small separation between oxygen atoms, it is possible to calculate a cluster size distribution nS, defined as the occurrence probability of clusters of size S, within Graphenion to measure the number of H2O molecules and H3O + ions in a cluster. The mean cluster size is given by