(528j) A Potential-Dependent Thiele Modulus to Quantify the Effectiveness of Porous Electrocatalysts
AIChE Annual Meeting
Wednesday, November 10, 2021 - 5:45pm to 6:00pm
In this talk, we will describe a general framework to quantify the effectiveness factor as functions of particle and reactant properties, applying both Tafel and ButlerâVolmer kinetics to one-dimensional reaction-diffusion through a porous sphere. Internal transport effects from diffusion through the catalyst pores and external transport effects resulting from reactant diffusion across the boundary layer surrounding the particle will be assessed. From this analysis, we will discuss design principles for electrocatalyst sizing based on desired utilization efficiency, and compute the interfacial current density with and without external transport as a function of applied overpotential. Our findings reveal markedly lower catalyst utilization for electrocatalysts in typical aqueous electrolytes, and the need to develop hierarchical structured electrocatalysts to mitigate diffusional pore-scale losses. To this end, we will extend the model to other common catalyst geometries using a simple shape factor analysis. Lastly, to highlight the utility and generalizability of the approach, we will apply the framework to the oxygen reduction reaction at a polymer electrolyte fuel cell, assessing the effect of ohmic and transport losses across multiple length scales on fuel cell performance. We anticipate that the framework presented is broadly applicable to porous electrocatalysts leveraged across a range of conditions encountered in electrochemical engineering applications.
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