Three-Dimensional Multiphysics Modeling of Bipolar Electrochemical Graphite Exfoliation and Graphene Deposition

Bipolar electrochemistry drives graphite exfoliation, transport of graphene-related species, and electrodeposition simultaneously in one reactor through a wirelessly polarized graphite electrode. Because these processes are coupled within the same electrolyte, the local ion concentrations, graphene-related species concentration, and current density that control the deposition are difficult to measure experimentally. A three-dimensional multiphysics model coupling charge, species, momentum, and energy conservation was developed, in which DFT calculations on simplified static reference systems provided the effective intercalation numbers of the OH- and H3O+ assisted exfoliation pathways (x = 4 and y = 3) for the COMSOL-based continuum simulations. The model simulated graphite consumption and feeding electrode deposition under different operating temperatures, graphite rod arrangements, and reactor geometries. Raising the temperature from 25 to 80 °C increased the simulated 24 h current density by approximately 82%. Adding a second pair of graphite rods increased the current density by approximately 16%, almost independently of the pair spacing, whereas the deposition was maximized when the spacing equaled the feeding electrode width (s/l = 1). Increasing the rectangular reactor width from 3 to 8 cm reduced the deposition thickness by approximately 60% while the current density decreased by only 9%.