Ames Goldsmith Corporation is working on low-iridium anode catalysts amid concerns over whether iridium reserves could support a scale up of polymer electrolyte membrane (PEMw) electrolysis.

Precious metal chemistry specialist Ames Goldsmith Corporation, through their Ames Goldsmith Ceimig, Dundee & Ames Advanced Materials, New Jersey divisions, is readying to launch a PEM anode catalyst with less than 15% of the iridium of rival products.

“Over the last three years we have carried out a cross-company development programme, using our scientists from the USA and UK, to develop a state-of-the-art, next-generation catalyst fit for the iridium demand profile in 2050,” says Wayne Thornhill, sales manager at the company.

Provisionally called HyPer WE53s, the product uses iridium deposited on a platinum-based support chemistry and is fully stable in the conditions at the anode. Platinum has a proven track record of stability under electrolyser anode conditions, and is used to protect flow plates.

PEM electrolysers are seen as important for green hydrogen production, with 40% of an estimated 100GW of electrolyser capacity by 2030 expected to use the technology. Global electrolysis capacity is set to rise to an estimated 3,585GW by 2050, based on ambitious targets globally.

At the end of 2022, more than 30 countries had put in place national hydrogen policies to decarbonize their energy requirements in pursuit of net zero emissions targets by 2050.

Electrolyser volumes are set to be boosted especially with the recent introduction of the Inflation Reduction Act in the USA and the REPowerEU hydrogen roadmap in the European Union, coupled with a new EU Green Deal Industrial Plan.

However, PEM’s presence in the electrolyser technology ecosystem could depend on iridium availability. Historically only around eight tonnes of iridium are mined annually, as by-product of platinum production. The current loading of iridium in PEM electrolysers is between 1g and 2.5g per kilowatt.

“The low end of this estimation, assuming the use of a catalyst such as iridium black [more than 98% iridium], equates to 40 tonnes of iridium required by 2030 for 40GW of PEM electrolysis and 1,430 tonnes by 2050,” says Thornhill.

“This level of iridium usage is not achievable and causes many people to question the viability of PEM electrolysis as a long-term solution in the fight against climate change.”

Ames Goldsmith, which has been selling into the market for over 15 years, has long been a champion of low-iridium catalysts for PEM technology. Ames Goldsmith’s bestselling product for the electrolyser market is HyPer WE 550, an iridium ruthenium oxide.

This product contains only two-thirds iridium and has an extremely high surface area, meaning small amounts can be used to achieve the same level of activity as in rival products.

Testing and in-use feedback shows that HyPer WE 550 offers equivalent performance to standard iridium oxide, with lower degradation rates. The accelerated stress tests performed by the company’s university partners were designed to simulate up to 100,000 hours of use.

Industry-wide use of HyPer WE 550 would allow the PEM industry to scale up to 2030 without overly stressing iridium reserves.

Typically, only 0.3g per kilowatt of iridium is required when using HyPer WE 550, meaning 12 tonnes of iridium would be needed for 40GW of PEM electrolysis by 2030 and 430 tonnes would be required by 2050.

“This is a significant improvement in iridium demand and means that there is currently a viable product available, which is produced at scale, which can easily achieve the demand rates well into the mid-2030s,” says Thornhill.

Beyond this period, a need for improvement in iridium loadings could be achieved to some extent through further alloying of metals.

Another technology route being developed is to optimise the use of iridium by depositing a thin layer of iridium nanocrystals on the surface of a support, much in the same way that platinum is deposited on carbon for use in fuel cells. This is the approach used for HyPer WE53s.

To date, many companies have been using supports selected for their durability in the highly oxidising current densities and high acidity found at the anode of the electrolyser.

Carbon is not a viable support in these conditions and supports such as titanium or tin oxides and doped variants of these oxides have been the focus for many companies.

Whilst this technology will aid in limiting the amount of iridium required, the reduction is limited to around 45% of the catalyst because of a requirement to conduct electricity across the surface of the membrane.

When using a non-conductive support, such as TiO2, the metal on the surface is required to provide both the conductivity and the catalysis requiring a high loading of metal.

This new grade, HyPer WE53s, uses <15% iridium supported on a platinum-based support chemistry. Testing has shown comparable performance and stability to iridium oxide of HyPer WE550.

Adoption of this grade should result in iridium loadings of less than 0.06g per kilowatt, meaning the 40GW of PEM electrolysis required by 2030 will only require 2.4 tonnes of iridium and the 1,430GW of PEM by 2050 will require 86 tonnes.

Given a ramp up in electrolyser production, Ames Goldsmith believes this volume should be readily achievable, especially if coupled with developments in PEM component recycling. The selection of a platinum-based support is also supportive of future iridium mining.

Iridium only accounts for up to 4% of the mining basket and therefore companies will not mine for iridium alone. By including a larger proportion of platinum in its products, Ames Goldsmith hopes to prompt the production of iridium.

“This is an important factor going forward as platinum demand reduces over the coming decades with the decline in internal combustion engine vehicles,” says Thornhill.

Despite the relative high cost of platinum, adoption of this new grade should reduce electrolyser costs by two thirds, according to Ames Goldsmith.

An analysis by International Renewable Energy Agency shows that the anode catalyst makes up just 2.7% of current total electrolyser cost, Ames Goldsmith says.

Using HyPer WE 53s would reduce this to less than 0.9% of the total cost, making PEM electrolysis more competitive with alternative electrolysis methods, the company claims.