UC Irvine

Separators or membranes are required in all electrochemical devices to prevent product crossover while maintaining a large ionic conductance. In solar fuels devices, and electrolyzers and fuel cells, separators must also support pressure differentials and serve as robust barriers to reactive chemical intermediates. Many different ion-exchange materials exist for this purpose but no single material has been identified as a clear front-runner for solar fuels applications. Described herein are state-of-the-art ion-exchange membranes, including cation conducting, anion conducting, mixed conducting, proton selective, and electron conducting, which may be useful in solar fuels devices. In addition, porous separators that afford mixing of electrolyte are also discussed in the context of near-neutral pH electrolytes. Analogous to fuel cells, solar fuels devices that are fed with water vapor are described, and possible membrane requirements for integrated tandem solar fuels devices are presented and discussed. Interfaces between the membrane and other components of solar fuels devices are briefly described as a new field with many opportunities for additional research.