Analysis of Gas Permeation Phenomena in a PEM Water Electrolyzer Operated at High Pressure and High Current Density

Abstract

In this study, on-line mass spectrometry is used to determine hydrogen permeation during proton exchange membrane water electrolyzer (PEM-WE) operation for a wide range of current densities (0–6 A cm−2) and operating pressures (1–30 bar, differential pressure). H2 permeation measurements with a permeation cell setup, i.e., without applying a current, show a linear correlation between permeation rate and H2 partial pressure, indicating diffusion as the main crossover mechanism. Measurements with full membrane electrode assemblies (MEAs) during PEM-WE operation reveal a significant increase of the gas permeation rate at high current densities, by up to ≈20-fold at 1 bar H2 and up to ≈1.2-fold at 30 bar H2 (Nafion® 212 or Nafion® 117 membrane; Ir-black (anode) and Pt/C (cathode)). Recently, H2 super-saturation of the ionomer phase in the cathode catalyst layer was shown to be the reason for this increase, and we discuss the impact of this effect for different electrode compositions and operating conditions. Finally, the determined H2 permeation rates and electrolyzer performance are used to discuss the overall PEM-WE efficiency for different membrane thicknesses and it is shown that the formation of an explosive gas mixture in the anode at low current densities requires additional mitigation strategies.

A high-performance, durable and low-cost proton exchange membrane electrolyser with stainless steel components

“…If the curve would present hysteresis it would be an indication of mass transport losses12 caused by Nb/Ti coating on the ss-PTL or degradation, as shown in Fig.6a. The performance of the PEMWE cell with stainless steel components is comparable to the highest performances reported up to now by renowned R&D institutes in electrolysis 31,37,53,54. However, thin membranes such as Nafion 212 are not yet suitable for industrial PEMWE since they degrade much faster than Nafion 115 leading to an increased H 2 crossover into the O 2 stream and…”

“…In this work we aim to use the lowest cost materials available, that is stainless steel meshes and plates to construct the PEMWE cells, and the achieved performances are comparable to other reports that use baseline sintered Ti-PTLs. 31,37 In Fig. S2 (ESI †) we show a comparison between the polarization curve of Nb/Ti/ ss-PTLs in Fig.…”

Understanding Degradation Effects of Elevated Temperature Operating Conditions in Polymer Electrolyte Water Electrolyzers

“…The hydrogen content in oxygen represents a safety issue, with 4% hydrogen in oxygen as a lower explosion limit. 63,70 Operation of PEWE is therefore often restricted to a safety limit of 2% hydrogen in oxygen on the anode side. Moreover, industrial electrolyzers are operated at differential pressures of up to 30 bar a , which further increases hydrogen permeation.…”

Structures and properties of polymers in ion exchange membranes for hydrogen generation by water electrolysis

“…13 These membranes have been well studied and characterized. 71,72 It has been well documented that although these membranes exhibit high performance and stability owing to the presence of both fluoro and sulphonic acid groups, they suffer critically from high cost and other issues. 20 Therefore, one of the research-focuses within the domain of PEMs is to minimize the use of Nafion and/or to increase its efficiency.…”

“…Commercial Nafion membranes, having perfluorosulphonic acid structure, have been the material of choice both in PEM‐based fuel cells and water electrolyzers 13 . These membranes have been well studied and characterized 71,72 . It has been well documented that although these membranes exhibit high performance and stability owing to the presence of both fluoro and sulphonic acid groups, they suffer critically from high cost and other issues 20 .…”