Abstract
Cation exchange membranes need to have high permselectivity for protons to make these membranes suitable for, for example, energy storage devices. Here, we present the proof of concept for a proton selective membrane made of hydrochloric acid-doped ice. The proton selectivity of this acid-doped ice membrane is the result of defects in the ice structure, caused by the acid. Ice membranes were made from different hydrochloric acid concentrations (0.1-2.0 M). The proton permselectivity of all ice membranes was above 99.7% when both Na+ and K+ were present. The resistivity decreased exponentially with the concentration of acid in the ice membrane, reaching a value of 12 Ω.cm. The ice membranes were tested in an electrochemical cell using the Fe/Fe2+ and Fe2+/Fe3+ redox couples, and a power density of 7 W/m2 and OCV of 0.87 V were measured. The resistance of the ice membrane increased with time as protons moved from the ice structure, as determined from the higher pH of the ice after melting. These expelled protons (and corresponding counter charged ions) were not replaced by other mobile cations, indicating a permanent loss in conductivity, but not selectivity. To apply the ice membrane as a selective separator for protons in energy storage devices in the future, the membrane thickness should be reduced and the protons should be retained inside the ice.
Highlights
Renewable energy technologies such as wind and solar power are facing the problem of matching irregular production with fluctuating demand
To create the ice membrane, the cell was filled with a solution with the desired concentration of hydrochloric acid of 0.1, 0.5, 1.0 or 2.0 M HCl solution (Table 1)
To make sure that the window dividing the two compartments was fully formed, some of the acid solution from either of the two sides of the cell was removed and the ice membrane was considered complete if the liquid level in the opposite compartment remained the same
Summary
Renewable energy technologies such as wind and solar power are facing the problem of matching irregular production with fluctuating demand. Storage of (large quantities) of electrical energy is very much in need to dampen this difference in supply and demand. The electricity produced by renewables can be used for the formation of a pH gradient in the acid-base-flow battery.[1,2] In this acid-base battery, water is dissociated into protons and hydroxide ions by the use of a bipolar membrane, while charging the battery. In this way, electrical energy is stored in a proton gradient. The energy stored in this proton gradient can be harvested by recombining the protons and hydroxyl in the junction of the bipolar membrane in a process called reverse
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
