Brief History of Porous Electrode Theory

The importance of structural effects in gas diffusion electrodes had been realized long before the development of the current generation of CLs for PEFCs started. The basic theory of gas diffusion electrodes, including the interplay of reactant transport through porous networks and electrochemical processes at dispersed electrode-electrolyte interfaces, dates back to the 1940s and the 1950s (Frumkin, 1949). Later work identified the importance of total surface area and utilization of electrocatalyst in porous electrodes (Mund and Sturm, 1975). 

A series of seminal contributions by R. De Levie paved the way for the widespread use of electrochemical impedance measurements in the characterization of porous electrodes (Levie, 1963, 1967 Raistrick, 1990). The transmission line approach of De Levie constituted the seed for the study of interfacial phenomena in electrodes with fractal surfaces (Halsey, 1987 Kaplan et al., 1987 Pajkossy and Nyikos, 1990 Sapoval, 1987 Sapoval et al., 1988 Wang, 1988). 

Major contributions to the development of the macrokinetic or macrohomoge-neous theory of porous electrodes were made by Yu. A. Chizmadzhev, Yu.G. Chirkov, 

Effectiveness factor approaches Macrohomogeneousmodel of ionomer-bound CL Structural (percolation) model of ionomer-bound CL Structural model coupled with water balance in pores Thin-film morphology of ionomer in CL Hierarchical Model, coupling of meso-and macroscale 

FIGURE 3.3 A timeline of developments in porous electrode theory and catalyst layer modeling. 

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