Degradation Mechanisms in Advanced MEAs for PEM Water Electrolyzers Fabricated by Reactive Spray Deposition Technology

Abstract

Proton exchange membrane water electrolyzers (PEMWEs) have demonstrated enormous potential as the next generation hydrogen production technology. The main challenges that the state-of-the-art PEMWEs are currently facing are excessive cost and poor durability. Understanding the failure modes in PEMWEs is a key factor for improving their durability, lowering the precious metal loading, and hence cost reduction. In this work, reactive spray deposition technology (RSDT) has been used to fabricate a membrane electrode assembly (MEA) with one order of magnitude lower Pt and Ir catalyst loadings (0.2-0.3 mgPGM cm-2) in comparison to the precious metal loadings in the stat-of-the-art commercial MEAs (2–3 mgPGM cm-2). As fabricated MEA with an active area of 86 cm2, has been tested for over 5000 hours at steady-state conditions that are typical for an industrial hydrogen production system. Herein, we present and discuss the results from a comprehensive post-test analysis of the MEA of interest. The main degradation mechanisms, governing the performance loss in the RSDT fabricated MEA with ultra-low precious metal loadings, have been identified and discussed in detail. All failure modes are critically compared and the main degradation mechanism with the highest impact on the MEA performance loss among the others is identified.

In Search of Lost Iridium: Quantification of Anode Catalyst Layer Dissolution in Proton Exchange Membrane Water Electrolyzers

“…However, in their extended degradation experiments (5000 h of steady-state operation at 1.8 A cm −2 ), Zeng et al obtained a significantly lower catalyst lifetime. 16 This leads to questions of whether the dissolution and redeposition of Ir is affected by the protocol applied or if they are time-dependent processes. These questions will be addressed in future works.…”

“…On the other hand, we recently reported an initial increase followed by a stabilization of Ir amount in the closed anode loop when the PEMWE tests were performed in a metal-free setup . The migration of dissolved Ir species through the membrane and the cathode catalyst layer (CCL) has so far been studied through physicochemical characterization of the aged MEAs, with the main focus being placed on the ACL/membrane interface. ,, It was shown that Ir dissolved from the ACL diffuses through the membrane to the CCL, forming an IrO 2 band adjacent to the ACL, precipitating with the dissolved Pt ions within the membrane and even depositing in the cathode. , …”

“…Comparison of Ir stability in AMS (brown bar) and MEA systems reported in this and the previous work of our group (the first and the second blue bar from the top, respectively) as well as in the work by Zeng et al (bottom dark blue bar), expressed through the predicted catalyst lifetime metric. The previously reported results of our group were recalculated based on the contributions of different parameters to the Ir mass balance presented in Figure b. , …”

Advancing the Rigor and Reproducibility of Electrocatalyst Stability Benchmarking and Intrinsic Material Degradation Analysis for Water Oxidation

“…Additionally, high current densities can cause increased gas bubble formation, resulting in mechanical stress and CCM delamination, as well as increased oxygen concentration at the anode, which can accelerate corrosion or passivation processes and increase Ohmic losses . Under a more common, moderate operation of 1–2 A/cm 2 , Ir and IrO 2 are generally accepted as being sufficiently stable against dissolution for long-term PEM electrolyzer operation when a moderate to high catalyst loading (1.5–2.2 mg Ir /cm 2 ) is employed. ,,, However, recent work by Zeng and co-workers points out that the governing degradation mechanism of an MEA with low Ir loading tested for over 5000 h of steady-state operation was Ir dissolution from the anode catalyst layer . This work reported that 30% of Ir from the anode catalyst layer dissolved and ultimately caused critical chemical and mechanical damage to the membrane.…”

Control of Wind Farm Power Output for Green Hydrogen Production without a Grid Connection

“…One potential improvement for PEM electrolysers is their relatively poor durability [16]. To better understand the degradation of electrolysers connected to RES, [17] subjects a PEM electrolyser to fluctuating power supplies by alternating high and low current densities.…”