Before modelling the iodine phase evolution, we generate a 3D model of the empty nanoporous carbon structure using a fit to the ex situ SAXS curve of the empty carbon electrode and the concept of clipped Gaussian random fields. Detailed descriptions of the procedure are given in Refs. . In brief, a Gaussian random field ( ) is the sum of cosine waves with wave vectors distributed according to their power spectral density `N(a) and phase factors b ^ randomly distributed between 0 and 2c. ( ) = d 2 e f cos (g h • -b