All‐Hydrocarbon MEA for PEM Water Electrolysis Combining Low Hydrogen Crossover and High Efficiency

Abstract

Hydrocarbon ionomers bear the potential to significantly lower the material cost and increase the efficiency of proton‐exchange membrane water electrolyzers (PEMWE). However, no fully hydrocarbon membrane electrode assembly (MEA) with a performance comparable to Nafion‐MEAs has been reported. PEMWE‐MEAs are presented comprising sPPS as membrane and electrode binder reaching 3.5 A cm−2 at 1.8 V and thus clearly outperforming state‐of‐the‐art Nafion‐MEAs (N115 as membrane, 1.5 A cm−2 at 1.8 V) due to a significantly lower high frequency resistance (57 ± 4 mΩ cm² vs 161 ± 7 mΩ cm²). Additionally, pure sPPS‐membranes show a three times lower gas crossover (<0.3 mA cm−2) than Nafion N115‐membranes (>1.1 mA cm−2) in a fully humidified surrogate test. Furthermore, more than 80 h of continuous operation is shown for sPPS‐MEAs in a preliminary durability test (constant current hold at 1 A cm−2 at 80 °C). These results rely on the unique transport properties of sulfonated poly(phenylene sulfone) (sPPS) that combines high proton conductivity with low gas crossover.

Anion Exchange Ionomers: Impact of Chemistry on Thin‐Film Properties

“…The relatively low free volume fraction observed in hydrocarbon‐based ionomers, particularly QA‐PPO, can contribute to the lower gas permeability and higher water uptake observed in these ionomers than perfluorinated ones in fuel cells and electrolyzers. [ 9,35 ]…”

The effect of ionomer content in catalyst layers in anion-exchange membrane water electrolyzers prepared with reinforced membranes (Aemion+™)

“…The spray coating procedure was adapted from Klose et al, 6 where details can be found. An ultrasonic spray coater (SNR 300, Sonocell) was used with a 60 kHz ultrasonic nozzle (Sonaer NS60K Atomizer) set to 90% power.…”

“…4 Many emerging AEMs are based on uorine-free, hydrocarbon polymers with the potential advantage of lower synthesis cost compared to incumbent uorinebased membrane chemistry. 5 Some hydrocarbon PEM and AEM membranes (such as sulfonated poly(phenylene sulfone), sPPS 6 or Tokuyama 201 7 ) have shown a promising reduction of the gas crossover compared to the standard uorine-containing PEM (e.g. Naon) or alkaline electrolysis diaphragms.…”

“…2 This may facilitate operation at differential pressures and utilizing thinner membranes. 2,6 While AEM water electrolyzers are an emerging technology, 8,9 wide-spread use is still limited because of issues of stability of the membranes and constituent polymers, effects critically exacerbated at the elevated temperatures required for efficient electrocatalysis. 3,32 For membranes, mitigation strategies addressing mechanical and hydrolytic stability include the adoption of woven or non-woven ber reinforcements of the membrane.…”

Main Hydrogen Production Processes: An Overview

“…As alternative, sulfonated poly(phenylene sulfone) (sPPS) combines high proton conductivity with low gas crossover can be used. It has been reported that the performance of the sPPS-MEAs is substantially better than that of Nafion N115-MEAs (3.5 A•cm −2 vs 1.5 A•cm −2 at 1.8 V) with the same catalyst loading and comparable membrane thickness [170].…”