Methods–A Potential-Dependent Thiele Modulus to Quantify the Effectiveness of Porous Electrocatalysts

(a) Two-dimensional representation of the modeling domain. (b) Electrocatalyst utilization based on particle sizing and desired activity. (c) Dimensionless polarization curves and (d) effectiveness factors as a function of overpotential for several kinetic rate constants.

Scientific Achievement

A generalizable potential-dependent Thiele modulus accounting for the relationship between electrochemical reaction kinetics and diffusion is presented for the design of porous catalyst materials for use in electrochemical reactors such as redox flow batteries.

Significance and Impact

Findings from this work reveal markedly lower catalyst utilization at increasing overpotential in spherical microparticle geometries, motivating the development of hierarchically-structured electrocatalysts to mitigate diffusional losses at the pore scale.

Research Details

  • The analytical framework balances one-dimensional reaction-diffusion through a porous catalytic sphere assuming Tafel or Butler-Volmer kinetic formalisms, leading to potential-dependent effectiveness factors.
  • Particle sizing guidelines based on catalysts utilization are developed.
  • A shape factor analysis enables generalizability to alternate electrocatalyst geometries (i.e., slab, annulus, cylinder).

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DOI: 10.1149/1945-7111/ac34ce

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