Understanding Degradation Mechanisms in PEM Water Electrolysis Under Dynamic and Static Operating Conditions

Hydrogen production by electrolysis has great potential to enable a decarbonized economy, although further effort is needed to decrease its cost to meet ambitious targets, such as the US Department of Energy Hydrogen Earthshot goal of 1/kg H2. 1 Achieving such low hydrogen production costs using polymer electrolyte membrane water electrolysis (PEMWE) will require decreasing the cost of input electricity while lowering capital costs through thrifting of iridium and other measures. An important opportunity to lower costs is the use of inexpensive intermittent electricity, either directly sourced from renewables or from grid leveling. However, previous studies have shown that dynamic cycling can accelerate degradation, especially when combined with low iridium catalyst loadings. 2 It is therefore necessary to further understand the relevant degradation mechanisms, mitigation strategies, and implications for water electrolysis deployment. Here we present the results of investigations to understand the degradation mechanisms in PEMWEs under dynamic and static operating conditions. This presentation will discuss the attribution of voltage degradation observed during long-term, constant-current operation as well as comparison of the degradation observed under cycled and static test conditions, with select results illustrated in Figure 1. This includes experiments designed to understand the transition between static and dynamic degradation behavior, differences in the degradation mechanisms, and opportunities for mitigation of dynamic degradation. We will further present investigations into the impacts of porous transport layer-catalyst layer interactions on anode catalyst degradation. Finally, we will discuss the implications of these results for guiding research priorities in PEMWE and developing operational and materials-based mitigation strategies. Citations: Energy. gov https: //www. energy. gov/eere/fuelcells/hydrogen-shot. S. M. Alia, S. Stariha, and R. L. Borup, J. Electrochem. Soc. , 166, F1164–F1172 (2019). Figure 1: Voltage over time profiles for durability tests comparing different current densities and cycle/hold protocols. All tests use anode/cathode catalyst loadings of 0. 4 mg Ir cm -2 /0. 1 mg Pt cm -2 and a Nafion N115 membrane, operating at 80°C. Figure 1