Studies of MEA Durability in Proton Exchange Membrane Water Electrolysis
Hydrogen production from proton exchange membrane (PEM) water electrolysis is attractive due to its simple and clean nature. Membrane and electrode assemblies (MEAs) of PEM electrolyzers typically use iridium (Ir) as an anode catalyst and Pt as a cathode catalyst. The durability of MEAs plays an essential role for the electrolyzers’ lifetime and cost. However, unlike the well-established MEA durability protocols of PEM fuel cells, there have been a lack of effective procedures for PEM electrolyzer MEA durability evaluation.
The objective of this work is to establish a series of test protocols that can help to rapidly evaluate PEM electrolyzer MEA durability. Three testing approaches have been used in this work, which include high-voltage hold (>1.8 V), voltage cycling (1.4 to 1.8 V or 2.0 V), and constant low-current operations. The electrochemical surface area (ECSA) and polarization curves of the MEAs will be obtained after each test.
Two categories of anode catalysts have been evaluated using the above durability test protocols: one is the commercial Ir black and the other is Ir supported on tungsten-doped titanium oxide (Ir/WxTi1-xO2) developed at Giner. The supported Ir/WxTi1-xO2 catalyst proves to possess 8-10 x higher mass activity than the Ir black. The MEAs made of these two anode catalysts have been evaluated at a variety of loading, low (0.1 mg/cm2), medium (0.4 mg/cm2) and high (1.0 mg/cm2). Figure 1 shows the durability of these two catalysts after voltage cycling from 1.4 V to 1.8 V: (a) 2 mg/cm2 Ir from Ir black; (b) 0.4 mg/cm2 Ir from Ir/WxTi1-xO2. It can be seen that at medium to high Ir loadings, these two catalysts demonstrates minimal performance decay after voltage cycling.
The morphology and structure of MEAs after durability tests will be characterized to correlate to their performance and to elucidate their degradation mechanisms.
Acknowledgement: The financial support is from the Department of Energy under the Contract Grant DE-SC0007471.