Back in the spring of 2015 at the ECS meeting in Chicago I had a definite pleasure to introduce audience to new twist to the way electrolytic hydrogen can be produced, i.e. via an electrolysis process that does not stress the utmost efficiency of the conversion, instead a paradigm of use was introduced that proposed high current operation instead⁽¹⁾. The idea was based on the premise that energy needed for the electrolysis process will in the near future be coming from environmentally friendly renewable technologies, energy that will be available in excess at times as building a reliable energy grid based on renewable technologies requires deploying a substantial overcapacity. The presence of such overcapacity would in all likelihood make low cost energy available, albeit at rather poorly predictable moments. It seemed therefore that deploying low cost electrolyzer farms could capture these low cost energy peaks and convert the temporary excess of power into hydrogen fuel that can be stored, transported, used industrially, converted back to energy at opportune moments or used to propel fuel cell vehicles. For such a scheme to be economical capital expenses associated with deploying electrolyzer farms would need to be substantially reduced. The single most relevant parameter here is the maximum operating current density, even at the expense of efficiency, such mode of operation can reduce electrolyzer installation costs proportionately (i.e. twice the operating current density, half the cost of the electrolyzer). An additional mitigating factor is that the efficiency losses (which at higher current densities are almost exclusively Ohmic) are relatively minor due to already rather high operating voltages of the. That combined with the expected low electrical energy cost during periods of overproduction can make CAPX dominant factor in determining economic viability of such installations.

This brings us to that presentation from three years ago at the 227^th ECS meeting in Chicago where we presented a very successful application of the 3M’s proprietary NanoStructured Thin Film (NSTF) catalyst technology to electrolyzer catalysts, i.e. an Ir-NSTF version of it, which at low, sub. 0.5 mg/cm² Ir loading produced respectable performance in an electrolyzer. What was at least at that time unique to our group was the ability of Catalyst Coated Membranes (CCMs) based on the aforementioned Ir-NSTF technology in combination with 3M’s low Equivalent Weight (E.W.) PerFluoroSulfonic Acid (PFSA) based membranes to reach previously unreported current densities approaching as high as 20 A/cm². Since then other groups have also reported increasingly higher current densities recorded in forms of polarization curves⁽²⁾, and we have reported very good durability of 3M’s Ir-NSTF catalyst in series of presentations^(3-5) where tests of up to 5,000 hours were conducted at typical for today current density of 2.0 A/cm² with minimal (actually record low) observed degradation rates (Figure 1.). This presentation will be a continuation of the above story with an attempt to answer the question that was asked but not yet adequately answered, namely whether such high current densities recorded in a brief periods of time performing polarization curve measurements can actually be sustained for any meaningful period of time. We will also touch on the potential mechanisms of CCM degradation at these very high current densities.

1. Krzysztof A. Lewinski, Sean M. Luopa, (invited) “High Power Water Electrolysis as a New Paradigm for Operation of PEM Electrolyzer” (abstract 1948), Spring ECS Meeting, Chicago, IL, May 2015.
2. Manfred Waidhas, (invited) “Business Opportunities for MW-scale PEM water electrolyzers”, (talk #7), 1^st International Conference on Electrolysis, Copenhagen, Denmark, June 12^th, 2017.
3. Krzysztof A. Lewinski, Dennis van der Vliet, and Sean M. Luopa, “NSTF Advances for PEM Electrolysis - the Effect of Alloying on Activity of NSTF Electrolyzer Catalysts and Performance of NSTF Based PEM Electrolyzers” (Abstract 1457), Fall ECS Meeting, Phoenix, AZ, Oct 2015.
4. Krzysztof A. Lewinski, Dennis van der Vliet, and Sean M. Luopa, “NSTF Advances for PEM Electrolysis - the Effect of Alloying on Activity of NSTF Electrolyzer Catalysts and Performance of NSTF Based PEM Electrolyzers”, (10.1149/06917.0893ecst), ECS Transactions, 69 (17) , p. 893-917 (2015).
5. Krzysztof A. Lewinski, “Operation of low-temp. electrolyzers at very high current densities: a pipe dream or an opportunity?”, (talk #52), 1^st International Conference on Electrolysis, Copenhagen, Denmark, June 14^th, 2017.