Rotating Disk Electrode Coated by a Porous Film

2 Rotating Disk Electrode Coated by a Porous Film 

Porous nonreacting layers covering reacting metallic interfaces may slow down the mass transfer of diffusing species. This decrease includes the effect of the diffusiv-ity Dy, as well as that of the layer thickness Sf. This problem was discussed in a more general way in Chapter 11. 

In the porous layer, the concentration distribution is determined only by molecular diffusion following 

For simplicity, the origin of the coordinate y is taken to be at the metal-layer interface and that of yf is at the layer-fluid interface (jff = y — Sf). 

Associated with equations (15.53) and (15.54) are boimdary conditions tiiat express the continuity of the concentration fields and of the fluxes for the steady state as well as for the time-dependent quantities. For y = 5f oxyf = 0, 

---