PEM electrolysis – the future or just another platinum grade problem?

PEM electrolysis

PEM electrolysis – the future or just another platinum grade problem?

Authored by Climate LinkUP Energy Correspondent & Ambassador, Courtney Quinn – co-host of the upcoming webinar on 24 January 2023: ‘The Future of Green Energy’ 

Hydrogen has a huge role to play in the path to net-zero and it will be vital in the decarbonisation of “hard to electrify” areas but there is also an existing demand for low carbon hydrogen in industries such as food production. As much as half of the world’s food production relies on ammonia fertiliser which, more often than not, uses hydrogen produced from fossil fuels1. The need for low carbon hydrogen is present today and demand is only set to increase. In August 2021 the UK government published the “UK Hydrogen Strategy” document which details the UK’s plan for hydrogen’s role in the path to net-zero2. The UK is aiming for 10GW of low carbon hydrogen production capacity by 2030 and in order to reach this target sustainably we must consider the impact of the technologies used to produce the hydrogen.

Hydrogen can be obtained from various raw material sources with varying environmental impacts. Water electrolysis accounts for less than 5% of all the global industrial hydrogen despite being one of the methods with the lowest environmental impact3. The primary reason for water electrolysis not accounting for more is due to cost – hydrogen produced from electrolysis is currently vastly outpriced by higher carbon hydrogen produced using more mature but carbon-based pathways including natural gas reforming. The Hydrogen Shot clean hydrogen cost target stands at $1/kg of H2 by 2030 which is a fifth of the cost when the target was set in 20214. The only hope of meeting this target whilst not compromising on carbon emissions is to improve the durability and performance of electrolysers whilst also reducing manufacturing costs – but herein lies the challenge.

PEM water electrolysis is one of the most promising hydrogen production methods and is ideal for use with electricity produced using renewable energies3. PEM water electrolysis enables the production of high purity hydrogen with no carbon emissions produced as a result of the process, however, the materials used to construct these electrolysers are often both costly and unsustainable.

Many PEM electrolysers use platinum at the cathode and iridium at the anode – both platinum group metals5. Iridium is one of the rarest naturally occurring elements with global production around 7 tonnes annually and in meeting targets for 2030 the global demand could be much greater than that6. In terms of platinum group metal reserves the vast majority of these reserves are located in South Africa (91%) with Russia (6%) and Zimbabwe (2%) following. The US government has acknowledged that platinum group metals and the supply deficit is a critical issue and so it is vital that we look for alternatives to their use in electrolysers.

One potential method of reducing the reliance on platinum group metals would be to operate the elctrolyser at elevated temperatures which would improve reaction kinetics and allow for other electrode and catalyst materials to be explored. In changing the materials of the electrolyser both sustainability and production cost could be improved so what’s the challenge? Typically, operating temperature is currently limited by the membrane (perfluorosulfonic acid) which is only highly conductive when hydrated so as temperature increases the conductivity decreases7. Many research groups are exploring alternatives8,9, but much research has to be done and time is running out if we are to close this vulnerability in time to meet our 2030 targets without having a platinum grade problem on our hands.

  1. Industrial ammonia production emits more CO2 than any other chemical-making reaction. Chemists want to change that. Chemical & Engineering News https://cen.acs.org/environment/green-chemistry/Industrial-ammonia-production-emits-CO2/97/i24.
  2. UK hydrogen strategy. GOV.UK https://www.gov.uk/government/publications/uk-hydrogen-strategy.
  3. Shiva Kumar, S. & Himabindu, V. Hydrogen production by PEM water electrolysis – A review. Materials Science for Energy Technologies 2, 442–454 (2019).
  4. Hydrogen Shot. Energy.gov https://www.energy.gov/eere/fuelcells/hydrogen-shot.
  5. Kiemel, S. et al. Critical materials for water electrolysers at the example of the energy transition in Germany. International Journal of Energy Research 45, 9914–9935 (2021).
  6. Crooks, E. Why iridium could put a damper on the green hydrogen boom. https://www.woodmac.com/news/opinion/why-iridium-could-put-a-damper-on-the-green-hydrogen-boom/ (2022).
  7. Avramov, S., Lefterova, E., Penchev, H., Sinigersky, V. & Slavcheva, E. Comparative study on the proton conductivity of perfluorosulfonic and polybenzimidazole based polymer electrolyte membranes. Bulgarian Chemical Communications 48, 43–50 (2016).
  8. Smith, D. E. & Walsh, D. A. The Nature of Proton Shuttling in Protic Ionic Liquid Fuel Cells. Advanced Energy Materials 9, 1900744 (2019).
  9. Sean, G., Daniel, S., Joshua, G., Jones, R. & Walsh, D. A. Electroanalysis of neutral precursors in protic ionic liquids and synthesis of high-ionicity ionic liquids. Langmuir 33, (2017).

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