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Non-Steady-State Permeation through Membranes for Solar Fuels Systems

Membranes are used as separators in photoelectrochemical cells that convert sunlight into chemicals such as H2 and CO2 reduction products. Their purpose is to conduct ions while blocking crossover and reoxidation of molecular products. The design and systems models of these membranes requires knowledge of their performance and properties during the diurnal cycle, when light intensity and hence permeant concentrations change continually. Membrane theory has not been developed for this situation, so we are constructing reaction-diffusion models to gain an understanding of how non-steady-state permeation works. In this talk I will introduce the requirements for solar fuels systems, and describe a combined experiment-simulation-theoretical investigation of time-dependent permeation through rubbery and glassy polymer membranes. The simulations are multiscale, linking nanoscale to macroscale in space and time, and do not use adjustable parameters. This allows validated models to be predictive, and provides a framework for mechanism discovery. Some insights to physical processes that are not well studied in the literature but appear to be important will be described.

Created May 1, 2018, Updated October 1, 2018