Multicomponent transport of alcohols in an anion exchange membrane measured by in-situ ATR FTIR spectroscopy

Abstract

Multicomponent transport through membranes is encountered in many applications, including photoelectrochemical CO 2 reduction devices that convert CO 2 into alcohols. We report the use of in-situ ATR FTIR spectroscopy to quantify the permeability of Selemion AMV, a commonly used anion exchange membrane, to mixtures of alcohols. An in-situ ATR FTIR spectrophotometer probe inserted into a standard diffusion cell enabled straightforward measurement of membrane permeability in multicomponent transport experiments without the need to periodically remove aliquots from the diffusion cell. The solubilities of alcohols in Selemion AMV were measured using a standard desorption technique. The solution-diffusion model was used to calculate alcohol diffusivities in Selemion AMV from measured permeabilities and solubilities. The relative contributions of alcohol solubility and diffusivity to overall permeability are discussed, and changes in permeability, solubility, and diffusivity with changing composition in binary and ternary alcohol mixtures are described.

Toward predictive permeabilities: Experimental measurements and multiscale simulation of methanol transport in Nafion

“…Time-resolved concentration data are key to this process, and it is essential to be confident in their accuracy. As described in the Experimental Development section, we were able to identify and implement three improvements to the experimental methodology described previously 32,47 eliminating gas bubble formation, adjusting for instrument drift, and utilizing a two-point baseline during data analysis that enable a closing of the mass balance within 0.005 g methanol across the more than 3 days duration of the experiment ( Figure S4 of the SI). A closed mass balance supports confidence in the accuracy of the time-resolved downstream concentration profile as measured using infrared spectroscopy.…”

“…Ultraviolet, visible, and infrared spectroscopy, however, offer chemical specificity for organic species. Submergible UV–vis and IR spectroscopic probes can be used to monitor changes in solution composition in situ over time 32,38,39 . Implementing such technologies in liquid permeation experiments has enabled high‐sensitivity collection of time‐resolved concentration data from which membrane permeabilities can be calculated 32 …”

Monitoring multicomponent transport using in situ ATR FTIR spectroscopy

“…The receiver chamber was initially charged with 30 mL of ultrapure water and the in situ ATR FTIR probe was inserted into the sampling port, ensuring that the probe tip was fully wetted. Details of the experimental setup, including a photograph of the diffusion cell apparatus, can be found elsewhere [29].…”

“…The membrane permeability was then calculated by fitting time-resolved concentration data to a free volume model for ion and small molecule transport in hydrated films [21][22][23]27,28]. We have previously reported the use of this technique to measure the transport of alcohols, including mixtures of alcohols, in a commercial anion exchange membrane [29]. The methodology presented here is broadly applicable to the measurement of solute permeation through polymer membranes of any type and only requires that the solute of interest have measureable infrared absorption within the detection region of the ATR FTIR spectrometer.…”

Transport of Neutral and Charged Solutes in Imidazolium-Functionalized Poly(phenylene oxide) Membranes for Artificial Photosynthesis

“…While several studies have correlated salt transport to AEM structural and chemical properties, few studies have explored uncharged solute (e.g., alcohol) transport through AEMs. 22,23,31,[33][34][35][36][37] More studies are needed to understand the complexity of transport through diverse membrane materials in a range of applications, including artificial photosynthesis. 4,14 Imidazolium-functionalized poly(phenylene oxide)-based membranes offer a platform that enables explicit study of membrane structure and transport properties within the context of artificial photosynthesis.…”