(96f) Characterization of Multicomponent Transport in Membranes for Solar Fuels Devices

Ion conducting membranes are of interest for various energy applications including fuel cells and solar fuel generators. Within the context of artificial photosynthesis towards solar fuel production, membranes are required to facilitate the ion transport necessary to promote electrochemical water splitting and CO2 reduction while meeting additional selectivity and permeability demands. Generally, membranes that limit the crossover of CO2 reduction products are desired, as high rates of product permeation through the membrane typically reduces device efficiency. Herein, we demonstrate the use of in-situ ATR FT-IR spectroscopy to quantitatively resolve the concentration of single component and multicomponent mixtures of select CO2 reduction products; methanol, formate and acetate. We then apply this methodology to the in-situ monitoring of single component and multicomponent permeation across commercially available membranes such as Nafion. Emergent transport phenomena, where the transport of a small molecule solute is affected by the presence of another solute, are explored via multicomponent permeation measurements. Membrane permeabilities and selectivities derived from single component permeation experiments are found to deviate, in some cases significantly, from permeabilities and selectivities measured in multicomponent permeation experiments.