Electrofreezing of Supercooled Water at -0.5 °C Induced by Al and Mg Electrodes via a Chemical Cooperative Process of "Ice-Making Species" and Electric Field

Here, we report on the chemistry of electrofreezing of water near -0.5 °C as induced by aluminum and magnesium electrodes. We suggest that the processes are triggered by the action of hydrated Al3+ and Mg2+ ions or their hydrated hydroxides, as created by electrolysis and the electric field. The uniqueness of octahedral hydrated Al3+ and Mg2+ ions lies in their high polarizing power, which acidifies the coordinated water that interacts with the bulk water to create hexagonal ice-like architectures. The aluminum electrodes induce icing when used as an anode (+50 V), while magnesium electrodes induce icing either as an anode or cathode at the same voltage, where the formation of the hydroxide ions is plausible. Furthermore, molecular dynamic simulations suggest that these species induce in their surroundings, under the influence of the electric field, "ice-like" assemblies that trigger the icing process. Those simulations suggest that the order in which the species lower the entropy of the system is Al(OH)3 > Mg(OH)2 > Al3+ > Mg2+.