Ionomer-bonded hydrophilic catalyst layer

As discussed above, it is vital to extend the eontact area between the catalyst and the protonic ionomer in order to improve catalyst utilization. To meet this requirement, ionomer-bonded hydrophilie eatalyst layers have been developed. The hydrophilic ink, prepared by mixing the catalyst and ionomer directly, ensures sufficient contact between the eatalyst particles and the ionomer. It was found that an ionomer-bonded hydrophilic catalyst layer could improve Pt utilization by up to 45.4% [25],... 

Membrane-based Hydrophilic Catalyst Layer. Wilson and Gottesfeld [8, 21-23] suggested an ionomer-bonded hydrophilic catalyst layer prepared with the decal transfer method. The so-called decal transfer process includes two key steps (1) coating catalyst ink onto a blank substrate (e.g., PTFE film) then (2) transferring the coat onto the membrane (as shown in Figure 19.6). A typical preparation procedure is as follows ... 

Colloid Method In order to improve gas transport through the ionomer-bonded hydrophilic catalyst layer, some modified hydrophilic electrodes have also been developed. One technique is called the colloid method, which changes Nafion into a colloid state. The colloid ionomer (such as Nafion) can adsorb catalyst particles to form larger catalyst/Nafron agglomerates. It is believed that the colloid method benefits the construction of the CL microstructure and enhances gas transportation [41-45]. Uchida et al. [41, 42] first proved that butyl acetate with a e of 5.01 was the best solvent to form PFSI colloids for the preparation of a catalyst layer. The detailed steps are as follows ... 

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