Fabrication PTFE-bound

PTFE-Bound Catalyst Layer Fabrication Using... 

TicianeUi and co-workers [126] fabricated the low-platinum loading PEM fuel cells featuring PI PE-bound catalyst layers. Cheng and co-workers [128] developed conventional PI PE-bound catalyst layer electrodes for direct comparison with the current thin-film method. The typical process employed for forming the PTFE-bound catalyst layer MEA in their study is detailed in the following [125],... 

In his 1995 patent, Wilson and co-workers desalbed the thin-film technique for fabricating catalyst layers for PEM fuel cells with catalyst loadings <0.35 mg cm. In this method the hydrophobic PTFE employed to bind the catalyst layer is replaced with hydrophilic perfluorosulfonate ionomer (Nafion ). As a result, the binding material in the catalyst layer is composed of the same material as the membrane. Thin-film catalyst layers have been found to operate at almost twice the power density of PTFE-bound catalyst layers. This corresponds to an inaease in active area utilization from 22% to 45.4% when a Nafion -impregnated and PTFE-bound catalyst layer is replaced with a thin-fihn catalyst layer [128]. Moreover, thin-fihn MEA manufacturing techniques are more established and apphcable to stack fabrication [130]. However, utilization of 45% suggests that there is still significant potential for improvement. 

The two widely employed electrode designs are the PTFE-bound and thin-film electrodes. Other methods include those featuring catalyst layers formed with electrodeposition and vacuum deposition (sputtering). In general, electrode designs are differentiated by the structure and fabrication of the catalyst layer. 

The Nafion membranes are produced in this way and with a fabric backing such as PTFE or mixed PTFE - rayon fabrics These supporting materials improve the mechanical strength of the film and keep the dimensional changes in bounds In general, for chlor-alkali electrolysis, the side of the membrane with the highest resistance, selectivity and charge density is preferred toward the cathode side to limit the undesirable effects of the back flow of hydroxide ions into the anode chamber The anolyte side of the membrane polymer is thus less dense, less selective and more conductive than the catholyte side of the separator film ... 

---