This paper will consider the effects of catalyst composition on alkaline membrane electrolyzers with Sustainion™ membranes. In previous work^{1, 2}we have demonstrated that Sustainion™ membranes are stable at 60 °C for at least 1500 hours in 1 M KOH. Here we compare a number of base metal catalysts on the performance of an alkaline water electrolyzer.

Figure 1 shows the voltage needed to maintain 1 A/cm² in an alkaline water electrolyzer running at 60 °C in 1 M KOH. The blue circles in Figure 1 were taken with nickel nanoparticles on carbon paper on both anode and cathode. Initially we observed good performance, with a cell voltage of 2.1 V but the voltage increased by about 110 µV/hr over the 2000 hour run. The voltage needed to maintain 1 A/cm² decreased to 2.05 V when NiFeCo was substituted for Ni on the cathode, but we still observed a voltage rise of 44 µV/hr. We stopped the runs after 2000 hours and found that the membrane was still fine, but the carbon paper on the anode was degrading. So we replaced the carbon paper with metal cloth. We also substituted NiFeOx for Ni on the anode. The voltage needed to maintain 1 A/cm² dropped to 1.9 V, and was stable for 500 hours. The run is continuing.

It is useful to compare our results to those from the recent literature. The best previous alkaline water electrolyzers with base metal catalysts ran at currents below 0.25 A/cm² at 2 V^{3, 4} and even precious metal catalysts have had trouble maintaining 1 A/cm² at under 2 V^{5, 6}. These results show that alkaline water electrolyzers with Sustainion™ membranes and base metal catalysts show near precious metal performance.

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