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Su, H. et al. (2013). Membrane electrode assemblies with low noble metal loadings for hydrogen production from solid polymer electrolyte water electrolysis. AbstractHigh performance membrane electrode assemblies (MEAs) with low noble metal loadings (NMLs) were developed for solid polymer electrolyte (SPE) water electrolysis. The electro-chemical and physical characterization of the MEAs was performed by IeV curves, elec-trochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Even though the total NML was lowered to 0.38 mg cm -2 , it still reached a high performance of 1.633 V at 2 A cm -2 and 80 o C, with IrO2 as anode catalyst. The influences of the ionomer content in the anode catalyst layer (CL) and the cell temperature were investigated with the purpose of optimizing the performance. SEM and EIS measurements revealed that the MEA with low NML has very thin porous cathode and anode CLs that get intimate contact with the electrolyte membrane, which makes a reduced mass transport limitation and lower ohmic resistance of the MEA. A short-term water electrolysis operation at 1 A cm -2 showed that the MEA has good stability: the cell voltage maintained at ~1.60 V without distinct degradation after 122 h operation at 80 o C and atmospheric pressure.

Optimization of gas diffusion electrode for polybenzimidazole-based high temperature proton exchange membrane fuel cell: Evaluation of polymer binder in catalyst layer.

7 In this study thermal conductivities of Polymer Electrolyte Membrane Fuel Cell (PEMFC) Catalyst Layers 8 (CLs) were measured. The CLs were fabricated on a thin copper metal film, varied in composition and 9 measured both when dry and in the presence of residual water. In order to demonstrate and evaluate the 10 impact and relevance of the measurements, a 1-D thermal model was developed. 11 It was found that dry CLs, and CLs containing very small water content, had thermal conductivity values 12 of 0.07-0.11 W K −1 m −1 when compressed in the range of 5-15 bar compaction pressure. When adding 13 water up to 70 moles of water per mole of sulphonic group, it was observed that the water only had an effect 14 on the thermal conductivity with values much higher than those reported as the capacity of the ionomer. 15 The literature suggests, depending on the CL, that the ionomer of a CL can carry up to around 10 moles 16 of water per sulphonic group and that water content beyond this level is carried otherwise. We found that 17 for water content beyond 20 moles water per sulphonic group increases the thermal conductivity of the 18 CL considerably. Thus water that is not kept by the ionomer contribute to the increased effective thermal 19 conductivity of the CL while the water kept by of the ionomer has no impact. Absolute values of the thermal 20 conductivity of the wetted "super saturated" CLs were not possible to determine due to the statistical noise 21 in these experiments. The CLs were all found to compress irreversibly and to become incompressible above 22 10 bar compaction pressure 23 When considering wet porous transport layers (PTL) and moderately humidified CL, the PEMFC maximum 24 internal temperature difference increased by 33% when compared to the commonly assumed measured 25 thermal conductivities. Considering that the CL constitute less than 10% of the total PEMFC thickness 26 * Corresponding author; measurements and modelling. * * Corresponding author; catalyst layer sample preparation and development.