The investigated parameters are the dimensionless Darcy number (Da), the ratio of liquid and solid conductivity (τ ), the ratio of ohmic and kinetic resistance (δ), and the dimensionless applied current density (λ). The objective functions were normalized against their initial value in the optimization process representing the loss in a uniform-porosity electrode with the same configuration regarding the operating conditions and material properties. The normalized loss functions can be represented as performance metrics, where a positive number shows performance enhancement while a negative number shows performance decrease after the topology optimization. Fig. illustrates the final value of these metrics for 2D simulations after 150 iterations for the studied range of the effective parameters in flow regime defined by the base Darcy value of Da = 10 -5 .