PGM thrifting and its role in scaling new technologies

Platinum group metals (PGMs) are used in a wide range of products and applications. Though most commonly associated with autocatalysis, their uses are diverse and are set to expand in areas including clean energy, transportation, healthcare and digital technologies.

One reason PGMs can support applications at scale is their ability to deliver high performance in very small quantities. Through ‘thrifting’, researchers continually find new ways to get more performance from the same quantity of metal, improving what is known as ‘metal efficiency’. The impact can already be seen in autocatalysts: in 2016, European gasoline cars used approximately the same amount of PGM per kilogram of vehicle as they did in 1992, but produced around 70% less exhaust pollution. Continued research is what made the catalysts considerably more effective. By improving what each gram can achieve, thrifting can lower costs, support sustainability and enable wider use of PGM-based technologies.

Thrifting is already well established across PGM technologies, but there is still considerable scope to improve metal efficiency further. This blog considers three research questions that could help PGMs deliver even more value as established and emerging applications continue to develop.

1. How far can iridium efficiency in PEM electrolysis be improved? 

Proton exchange membrane (PEM) electrolysis provides a route to generating hydrogen, which will be vital for decarbonising 'hard-to-abate' sectors such as heavy-duty transport and shipping. Crucially for the energy transition, PEM is particularly well-suited to connecting with renewable energy sources.

Iridium oxide (IrO₂) is currently used in this process because it offers the best balance of activity and stability. But with perceived uncertainty surrounding global iridium supply, a lack of confidence among policymakers is limiting investment and fostering the belief that there may not be enough iridium to meet demand. Global iridium supply from mining is fixed at approximately 7–8 tonnes per year, with limited scope for increase. [i]

Though PGMs already operate within a closed-loop recycling system, to enable PEM electrolysis to scale without hitting a supply constraint, iridium-specific power density in PEM electrolysers needs to reduce by roughly an order of magnitude by 2050 — from around 0.3–2 mg/W today, depending on methodology, to a target of 0.04–0.05 mg/W. [ii]

This is the research challenge: at a given operating voltage, the output per mass of iridium needs to increase substantially. [iii] Progress is already being made through three complementary approaches: reducing cell resistance, lowering iridium loading per unit area and increasing the intrinsic activity of the catalyst. Researchers are also exploring different forms of iridium oxide to make more efficient use of the metal.

The scale of the target is significant, but current research indicates that progress is on track. The opportunity now is to build on that momentum and translate advances in catalyst performance into scalable electrolyser systems.

Find out more in our webinar with Mark Clapp: "Green hydrogen via PEM electrolysis"

2. Can platinum loadings in fuel cells be reduced further?

Thrifting means achieving the same or greater performance with less metal, reducing PGM intensity for more sustainable use. Energy efficiency is therefore not the only metric that counts: how much material is used to achieve a given output matters too. [iv]

As the world moves towards green technologies, the need to improve the efficiency of all systems will only grow, and this is also true of PGMs. But PGMs have a good precedent for this. Platinum loadings in FCEVs have fallen by more than 90% since the early 1990s as research has improved the efficiency with which the metal is used. Average loadings currently stand at around 45 g per vehicle across passenger and commercial vehicle classes. By 2050, JM modelling projects that this average could fall to between 15 g and 23 g per vehicle.

Recycling complements these gains by recovering platinum at the end of a fuel cell’s useful life and reducing net demand. Designing systems with recovery and recycling in mind could strengthen this closed loop further.

Efficiency gains in fuel cell loadings have already been substantial, but this remains an active research topic, with new advances in thrifting being achieved through ongoing development and optimisation of catalysts.

3. Beyond passenger vehicles: where else can thrifting support the scaling of new PGM-based technologies?

Platinum is a crucial component of heavy-duty fuel cells. However, most published durability datasets are based on passenger-vehicle operating conditions. Heavy-duty transport introduces different duty cycles and degradation mechanisms that remain comparatively under-studied.

The US Department of Energy has set a target platinum loading of 0.3 mg/cm² for fuel cells, compared with current levels of approximately 0.45 mg/cm². This defined gap gives researchers a clear target for further development. Importantly, reducing platinum loading has benefits beyond metal efficiency. Alongside increased power density and temperature tolerance, it is one of the material and design improvements needed to reach cost parity with diesel at $60/kW.

The same principle will matter as newer PGM applications develop. Fields such as spintronics and photocatalytic hydrogen production are still at an early stage, but their future economics will depend partly on how much performance can be achieved from a small amount of metal. Applying the lessons learned from autocatalysts, fuel cells and electrolysers could help these technologies progress towards wider use. [v]

Learn more in Iryna Zenyuk's webinar "Platinum electrocatalysts in fuel cells for heavy-duty vehicles"

Looking forward

PGM thrifting is not a response to a lack of metal. It is a well-established way of improving performance, lowering costs and making valuable materials go further. Combined with closed-loop recycling, it has already supported the development of technologies ranging from autocatalysts to fuel cells.

As PEM electrolysis, heavy-duty fuel cells and emerging applications continue to develop, researchers have an opportunity to extend this track record. Further improvements in metal efficiency could help these technologies scale sustainably while increasing the value delivered by every gram of PGM.