Performance of the High Temperature PEM Membrane Electrode Assembly
This communication will provide details on some of the HT-PEM MEA performance targets most recently achieved by Danish Power Systems, namely;
- MEA performances of >0.7 V cm-2 at 0.2 A cm-2 and >0.5 V at 0.8 A cm-2 using dry H2/Air.
- MEA lifetime of 12000 h at 0.23 A cm-2 using dry H2/Air with a degradation rate of <10 µV h-1.
- An integrated 5 kW stack/reformer system operating for 3000 h using methanol reformate as fuel.
The task of optimizing MEA performance is carried out using rotating disc electrode voltammetry and CO stripping/electrochemical surface area studies in order to improve electrode properties (porosity and phosphoric acid management). Investigations into MEA durability are conducted using post mortem analyses on MEAs tested under operating conditions. These studies are comprised of cross-sectional SEM imaging and X-ray diffraction to monitor catalyst layer/membrane degradation and catalyst particle growth, respectively. Studies using reformate have also led to promising results with an MEA performance of 0.58 V cm-2 at 0.385 A cm-2 with a degradation rate of 30 µV h-1 using wet H2 (30 mol%)/Air.
In addition to reaching performance benchmarks, a reduction in the standard deviation for MEA performance to <5% has been achieved through efforts aimed at improving the uniformity of the membrane and catalyst layer thicknesses.