FST coated membrane to reduce hydrogen system costs

Weinheim, Germany – Freudenberg Sealing Technologies (FST) has developed a new generation of catalyst-coated membranes (CCMs) for PEM electrolysis, the company announced 16 Oct.

The coated membranes require just 0.5 milligrams of iridium per cm2 and achieves a cell voltage of 1.74 volts at a current density of 3 amperes per cm2.

Iridium, a rare precious metal, is essential to the operation of PEM electrolyses: serving as a catalyst on the oxygen side of the membrane, where water is split.

Citing estimates from Fraunhofer ISE, FST said one gigawatt of electrolysis capacity requires 25,000 to 35,000 square meters of CCM.

At a loading of 0.5 mg/cm², this corresponds to approximately 125-175kg of iridium, the company noting that "many commercially available membranes require even more."

But using less precious metal is “beneficial only if efficiency is maintained,” noted FST, which has structured the catalyst layers so that the new CCM achieves “excellent” cell voltages.

As a result – and despite the low iridium content – the electrolyser requires less electricity per kilogram of hydrogen, thereby reducing operating expenditure.

FST went on to note that pressure on the hydrogen side of the membrane is often up to 30 bar higher than on the oxygen side.

As a result, it said, hydrogen can migrate through the membrane, creating an explosive mixture at concentrations of around 4% by volume or higher.

The company has, therefore, developed a proprietary safety technology for its CCMs.

This limits this migration so that the hydrogen content in the oxygen is less than 0.25% by volume – a “very high” safety margin.

“The cost of precious metals at the purchasing stage and electricity consumption during operation are two key factors in the economic viability of electrolysis,” commented Michael Milch, global head of new markets sales, CCM.

“Our new generation of CCMs addresses both, reducing total costs over the electrolyser’s life cycle without compromising safety,” according to the FST executive.