  Understanding how to structure a porous electrode to facilitate fluid, mass,
and charge transport is key to enhance the performance of electrochemical
devices such as fuel cells, electrolyzers, and redox flow batteries (RFBs).
Using a parallel computational framework, direct numerical simulations are
carried out on idealized porous electrode microstructures for RFBs. Strategies
to improve electrode design starting from a regular lattice are explored. We
observe that by introducing vacancies in the ordered arrangement, it is
possible to achieve higher voltage efficiency at a given current density,
thanks to improved mixing of reactive species, despite reducing the total
reactive surface. Careful engineering of the location of vacancies, resulting
in a density gradient, outperforms disordered configurations. Our simulation
framework is a new tool to explore transport phenomena in RFBs and our findings
suggest new ways to design performant electrodes.
