Iridium Catalysts for PEM Electrolyzers

Precious metal solutions around hydrogen generation with PEM water electolysis and other methods

Table of Contents

PEM Electrolysis: Catalysts for Electrodes

Alkaline and solid oxide electrolysis are two alternative technologies, whereas proton exchange membrane (PEM) electrolysis is increasingly gaining traction. It is expected that PEM electrolysis will play an important role in the transition towards a hydrogen economy.

Due to their excellent dynamic response time PEM electrolyzers are a perfect solution for storing curtailed, excessive renewable energy. Moreover, the advantage of high current density operation allows production of more Hydrogen from smaller set-ups compared to alkaline electrolysis. Due to the high-pressure outlet of hydrogen, PEM electrolyzer technologies are directly connectable to gas stations.

The production of green hydrogen through PEM electrolysis of water is a very suitable concept to enable storage, transportation and deployment of the produced renewable energy. Scale-up and cost reduction of green hydrogen represent the essential steps towards reducing the world´s carbon dioxide footprint.

Heraeus' PEM electrolyzer catalyst portfolio

Heraeus has been committed to precious metals for more than 160 years. Utilizing our profound expertise in precious metal catalysts we are now providing PEM electrolyzer catalysts.

Our product portfolio includes electrolyzer catalysts with different precious metal loadings.

In order to find the perfect solution to your needs, we are able to test in our fully equipped on-site laboratories and test center.


Iridium Black

Iridium Dioxide

Next Generation Low Iridium

Iridium Ruthenium Mix Oxide







High metal purity

High surface area material

Reduced Ir content, supported material

Reduced Ir content

Performance focus

Highly active, stable

Highly active, highly stable

Excellent activity and material efficiency

Excellent activity and material efficiency

BET surface area [m2/g]

21 - 25


20 – 150

120 – 200

Mass activity @ 1.45 Vcell (iR-free)* [A/g]

~ 79

~ 86

~ 570 (30%)

~ 450 (H2EL-50IrRuO)
 online available  online available online available
 45% Ir
 30% Ir
 10% Ir
 Contact Us
80°C, 5 cm² cell; anode 0.3 mg/cm²

Save 50–90% on Iridium compared to the market’s benchmark

We achieved breakthrough innovation by developing PEM electrolyzer catalysts with significantly reduced precious metal loading. H2-EL-xxIrO-S, low loading supported catalyst, will provide you with an up to three times higher catalyst performance while reducing the precious metal loading in the CCM by 50–90% in comparison to earlier generations.

The latest Heraeus innovation is a ruthenium-based catalyst for PEM water electrolysis. Alongside iridium, ruthenium also catalyzes the Oxygen Evolution Reaction (OER), which is the critical part in PEM electrolysis. Ruthenium possesses superior catalytic activity to iridium but lacks stability in the challenging conditions of a PEM electrolyzer stack.

The Heraeus concept solves this problem by combining both ruthenium and iridium oxide in a novel manner, enhancing stability while maintaining the increased catalytic activity provided by ruthenium.

This ruthenium-iridium oxide material class delivers an unprecedented activity boost. The catalyst can achieve up to 50 times higher mass activity than iridium oxide, and unlike ruthenium oxide alone, it remains stable in operational conditions. Accelerated degradation tests confirmed its stability after 30,000 cycles, presenting activity loss significantly lower than for ruthenium oxide and on par with iridium oxide.

The implementation of low-lowding iridium electrolyzer catalysts will be an important factor for the hydrogen ramp up.

Maximum New Electrolyzer Capacity
Iridium-thrifting is a critical factor to avoid potential material bottlenecks during the hydrogen ramp-up and has a high impact on material costs.

Iridium is a scarce metal, and the mining of primary material depends on the mining of platinum. Only about 9 tons of iridium are mined per year, and this amount is already in use in existing applications. Following the assumption that about 1.5 tons can be shifted to the hydrogen economy by using alternatives in other industries and tackling additional material streams in recycling, from 2023-2030 in total about 12 tons could be available.

On the other hand, globally 175GW of electrolyzer capacity has been announced until 2030. 40% of this capacity is expected to be built with PEM, which means 70GW PEM electrolyzer capacity.

With current catalyst loadings of in average 400kg/GW, this would need 28 tons of Iridium until 2030, more than most probably available (see above). With the reduced loading of 100kg/GW, which has been shown for the Heraeus next generation low-iridium catalysts (Möckl et al. JECS 2022), only 7 tons of iridium would be needed, which is in reach.

Your Expert for Catalysts for Electrodes

Steffen Kitzing

Steffen Kitzing

Hydrogen Systems, Recycling

Platinum Precursors for Bipolar Plates

An electrolyzer is made up from many e.g. 50-150 electrolysis cells which form a stack. Between the cells of a stack, so called bipolar plates divide the individual cells from each other and transport the water and product gases to and from the membrane. As well, bipolar plates are conducting electricity and help to cool the system.

There are several alternatives for bipolar plate materials. However, if metals are chosen, the bipolar plates need to be coated with a precious metal e.g. platinum to protect the metal from corrosion. Due to the high electric voltage in the cells would otherwise start unwanted electrochemical processes that lead to oxidation and consequently to degradation of the bipolar plate. The coating prohibits degradation of material and helps to extend lifetime and performance.

Utilizing Platinum DNS, the bipolar plates are coated in an electroplating process with a thin platinum layer. Heraeus delivers Platinum DNS in proven quality according to your specific needs. Get in Touch.

While the platinum coating helps to increase the lifetime of the electrolyzer stack, at some point it will nevertheless reach the end of its lifetime. Close the loop by utilizing our best-in-class recycling services for PEM cells, which are capable to extract the precious metals from the CCMs.

Your Expert for Precursors for Bipolar Plates

Detlef Gaiser

Dr. Detlef Gaiser

Chemical Products

Alkaline Water Electrolysis (AWE)

Most of the hydrogen that is produced today is coming from an Alkaline Water Electrolyzer (AWE). This technology has been around since decades and typically is not based on precious metals. In many cases it has been and still is the method of choice, while meanwhile some fields are emerging, where PEM electrolysis shows advantages, e.g. when it comes to high fluctuation of electrical input as typical especially for green energy.

As said, typically AWE is not involving precious metals. However, due to disturbances in the supply of some of the materials, including zirconia and nickel, also alternative materials are considered, some of them involving platinum group metals.

If you are interested exploring the contribution of possibilities for precious metals for AWE electrolysis our experts will be happy to assist.

Your Expert for Alkaline Water Electrolysis

Detlef Gaiser

Dr. Detlef Gaiser

Chemical Products

High Temperature Electrolysis (SOEC)

In SOE (solid oxide electrolysis), an SOFC (solid oxide fuel cell) runs in reverse mode. Instead of using the fuel cell to generate electricity from hydrogen, a voltage is applied and water vapor is split into hydrogen and oxygen. The actual cell can therefore be used for both purposes: to generate hydrogen as well as to use the hydrogen later for electricity recovery.

Precious metals are rarely used in the SOEC (Solid Oxide Electrolyser Cell) or SOFC itself. However, they are often used in connection with industrial processes that generate waste heat, because the required high operating temperatures are then already available. In these processes, components containing precious metals are then often involved elsewhere.

For fuel processing Heraeus supplies catalytic solutions for Reforming, Water Gas Shift or Gas Purification e.g. by Preferential Oxidation (PROX) or Selective Methanation – all tailored to the needs of an independent decentralized system operation. Please see our  gas purification page or on our solutions to a  fuel cell operation for further HeraPur® purification technologies.

As with other types of electrolysis, the hydrogen can be easily purified from unwanted components in SOE. You can find out more about this under  Hydrogen Purification .

Your Expert for High Temperature Electrolysis (SOEC)

Hendrik Spod

Dr. Hendrik Spod

Chemical Catalysts, Emission Catalysts

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