Smooth or Porous Electrodes

The porosity of an electrode surface will significantly influence its electrochemical behavior, especially because of a considerable decrease of the effective current density in case of materials with a high microporosity and consequently a large effective surface area. A well-known example is platinized platinum that can enable 

Dimensions and structures of pores in electrode materials will vary in an extremely wide range. The influence of the porosity on the electrode properties includes also mass-transfer effects. 

In order to extend the effective electrode area in principle three-dimensional electrodes are possible, for example, by using a packed particle bed, a sintered or foamed metal, or a graphite fiber felt. But the depth of the working electrode volume usually is only small (it is dependent on the ratio of the electrode and electrolyte conductivity, for example, [45]). 

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