Decal method

The nanostructured thin-film electrode was first developed at 3M Company by Debe et al. [40] and Debe [41], who prepared thin films of oriented crystalline organic whiskers on which Ft had been deposited. The film was then transferred to the membrane surface using a decal method, and a nanostructured thin-film catalyst-coated membrane was formed as shown in Figure 2.10. Interestingly, both the nanostructured thin-film (NSTF) catalyst and the CL are nonconventional. The latter contains no carbon or additional ionomer and is 20-30 times thinner than the conventional dispersed Pt/ carbon-based CL. In addition, the CL was more durable than conventional CCMs made from Pt/C and Nation ionomer [40]. 

Wilson, M. S. Membrane catalyst layer for fuel cells. US Patent 5,234,777,1993. Xie, J., Garzon, R, Zawodzinski, T., and Smith, W. Porosimetry of MEAs made by "thin film decal" method and its effect on performance of PEFCs. Journal of the Electrochemical Society 2004 151 A1841-A1846. 

Catalyst decal transfer [6, 78] In the catalyst decaling method, the catalyst ink is cast onto a PTFE blank for transfer to the membrane by hot pressing. A thin CL is left on the membrane when the PTFE blank is peeled away. Finally, the catalyzed membrane is re-hydrated and ion-exchanged to the if form by immersing it in hot dilute H2SO4 solution. 

PTlFE-boiided Decal method CL Sputteiiiia-depositioa CL... 

Krishnan NN, Prabhuram J, Hong YT et al (2010) Fabrication of MEA with hydrocarbon based membranes using low temperature decal method for DMFC. Int J Hydrogen Energy 35 5647-5655... 

FIGURE 2.6 Schematic flowcharts of the conventional decal method and the improved decal method for making a CCM [55]. (For color version of this figure, the reader is referred to the online version of this book.)... 

This procedure is depicted in Fig. 2.6 as the improved decal method. This is the simpler of the two methods. In addition, the fuel ceU testing results [55] indicated that the MEA made by the improved decal method yielded a better fuel cell performance. The authors attributed the superior cell performance to the higher porosity of the agglomerates in the MEA, which facilitated mass transport. 

Aside from being sprayed on the GDL, the catalyst ink can also be applied to the membrane to make a Nafion-bonded hydrophilic CL. To efficiently extend the three-phase reaction zone and reduce the Pt loading, Wilson et al. [37,39,41] developed a thin-fihn electrode using Nafion ionomer as the bonder. Their preparation process uses a decal method, the details of which are as follows [39] ... 

Decal Method In this technique, thin CLs are cast or spread onto a nonadhesive medium, and decal transferred onto an electrolyte by hot-press compression (similar to a clothes iron). This method is suitable for mass production of catalyst layers, with high tolerance and batch processing capability, although the physical bond between the electrode and the electrolyte must be carefully maintained. 

Wei et al. applied SPEEK/poly(ether sulfone) blend membranes to be used as an SPE for water electrolysis. MEA was fabricated by incorporating Ir anode layer and Pt cathode layer with the membrane by a decal method. An electrolytic current of 1655 mA cm" was obtained at 2 V and 80°C with the SPEEK-based MEA and under suitable fabrication conditions. Although the result was still not as good as a Naflon-based MEA, it also suggested that SPEK membrane could be an alternative to Naflon in SPE water electrolysis for hydrogen production. 

The catalysts were tested as PEM fuel cell cathodic catalytic layers on a unit cell-test bench 50 cm Membrane-Electrode Assembhes (MEAs) were prepared by the decal method as described in reference [2]. The electrolyte was a Nafion membrane, and the anode a commercial anode made from Pt-doped carbon black (40 wt.%, TKK) deposited by Paxitech onto a carbon felt (0.6 mgpt cm mixed with Nafion ). The thickness of the cathode was kept constant by keeping constant the carbon mass in the catalytic layer. The Nafion /carbon mass ratio of the ink used to prepare the MEAs was fixed at 0.5. After a standardized start-up procedure, polarization curves, i.e. the t/ceii = f(/m) curves, were measured by setting the cell voltage at each desired value for 15 min, which... 

Catalyst decaling In the catalyst decaling method described by Gottesfeld and Wilson (1992, 1992a) and Chun et al. (1998)... 

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