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Platinum group metals: an enabler for hydrogen, not a barrier

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Proton exchange membrane (PEM) electrolysers and PEM fuel cells rely on platinum group metal (PGM) catalysts, notably platinum and iridium. Many see this as a challenge, given the rarity and value of the PGMs. In fact, if used efficiently, these metals will actually facilitate the development of a resilient supply chain. To understand why this is, let’s look at the PGM landscape and the implications for PEM technologies in more detail.

By Margery Ryan, Principal Strategy Analyst for PGM, Johnson Matthey

Established mining operations – extensive reserves

What is the platinum group? It is a set of six precious metals – platinum, palladium, rhodium, ruthenium, iridium and osmium – that are close together on the periodic table and have a unique combination of useful properties that make them indispensable in their applications. They also occur in association with each other in mineral deposits. Most PGM mining occurs in its own right, although some PGM is also extracted as a by-product of mining for other metals (notably nickel and copper in Canada and Russia).

PGM mining is heavily concentrated in southern Africa, targeting igneous deposits in South Africa and

Zimbabwe that were formed two billion years ago by huge intrusions of magma from the Earth’s mantle that solidified below the Earth’s surface. These deposits are unique in their size, extending over

66,000 km2 (an area equivalent to Sri Lanka), and in the quantity of PGMs they contain.

Around 80% of the 190 tonnes (approximately) of primary platinum extracted every year comes from southern Africa. At the other end of the scale, 7 to 8 tonnes of iridium are mined every year, mainly as a minor by-product of platinum mining, and up to 95% of annual iridium extraction occurs in southern Africa. On the face of it, this could look like a geopolitical risk. But let’s dig a little deeper.

Platinum supplies from southern Africa
Resilient mine supplies from southern Africa since 1990 (https://matthey.com/pgm-demand-history)

PGM mining and refining is complex and technically challenging, so the sector is populated by several large, publicly quoted mining companies who are subject to stringent mining and labour regulation, rather than ‘artisanal’ mining. These well-established companies report annually on their production plus environmental, social and governance (ESG) performance. While the wider operating environment in South Africa and Zimbabwe has frequently been challenging, and risks remain as they do for mining operations anywhere, output from these operations has been remarkably resilient. At a political level, South Africa and Zimbabwe both recognise the enormous economic benefit of their PGM mining operations.

Thanks to the size of these deposits, and the vast quantities of PGMs they are estimated to host, we can be confident that enough PGM can be extracted to meet global needs for decades to come – although further investment will be needed to maintain and expand output. As the primary product of this mining, platinum’s central role in hydrogen technologies will be an important incentive for investment. And a strong business case for continued investment in platinum helps deliver a healthy supply of iridium.

2021 Platinum and Iridium Supply
Platinum and iridium total supply (primary and secondary) in 2021 (matthey.com/pgm-market-report-2022)

Recycling is a given for PGMs

PGM recycling happens routinely. Johnson Matthey was a pioneer in PGM recycling and is the largest global secondary refiner by volume of these metals today. Other companies also operate large secondary PGM refineries across the world that process substantial volumes of scrap material. The largest source of recycled metal returned to the market every year (known as secondary supply) is catalytic converters, recovered from scrapped diesel and gasoline vehicles. Collection and processing of these parts can be encouraged by recycling mandates but is primarily incentivised by the value of the PGMs they contain.

Already nearly a quarter of platinum supplied to the market every year is recycled metal. But even that is not the whole story: significant PGM recycling also happens in what we call ‘closed loop’. This is metal that is recovered from end-of-life products, processed, but then returned to the original owner for reuse in the same application, for example in PGM-based process catalysts. This closed-loop recycling considerably reduces the ongoing requirement for primary (mined) metal in a wide range of industrial applications.

This is particularly important for iridium, because the recyclability of iridium is often raised as a challenge. In fact, substantial quantities of iridium are circulating constantly in closed loop, generally unseen by the market (Johnson Matthey does not report closed-loop recycling in its supply and demand figures). Johnson Matthey and others have established efficient processes for recycling iridium. Although investment continues to optimise these processes, iridium in PEM components can be recycled today.

This points to two important advantages in using PGM: the first is that PGM recycling is value driven. The second is that PGM used in hydrogen technologies remains an asset that will be recovered and reused as much as possible. As with other industrial applications to date, we expect to see an inventory of recycled PGM building up within the hydrogen industry over the longer term.

Platinum is ready for a new market

When looking at any commodity, it is important to understand the balance between supply and demand. Platinum is currently in industrial oversupply: more of the metal is put on to the market every year than industrial users require. The ‘grouped’ nature of PGM mining explains this: in today’s market, palladium and rhodium, which are by-products of platinum mining, are undersupplied and in high demand by the automotive industry for catalytic converters. Therefore, it would not make sense to mine less platinum, because this would then also produce less palladium and rhodium.

2021 Platinum Demand
Platinum demand by application in 2021

The single biggest use of platinum today is in automotive emissions control catalysts, although platinum is much less dominated by automotive consumption than palladium and rhodium. But in the long term, this market will decline as the internal combustion engine is eventually phased out.

Platinum’s second largest market – jewellery – has been in decline for some years. The largest regional market for platinum jewellery is China and consumer spending patterns have shifted in that market. Globally, we expect almost 30 tonnes less platinum will be used in jewellery this year than in 2017.

Hydrogen technologies will therefore be replacing some of platinum’s older markets. Contrast this to the situation in the battery sector where users of metals such as lithium and nickel face stiff competition for supply, which has to expand dramatically amid sharply rising demand.

Minimising mineral intensity

That said, platinum is still a valuable and limited resource, and must be used efficiently. Considerable reductions to the intensity of platinum use in fuel cells have already been achieved through innovation, to around 30 g per vehicle (without compromising performance), and this ‘thrifting’ continues. It’s a familiar progression in the PGM industry: for example, the reliance of automotive emissions control on PGM has only been sustainable because of increasingly efficient metal use.

Only a few grams of PGM are needed to treat the pollutants in a gasoline vehicle’s exhaust to meet the stringent standards required today, and only a few grams will be needed to catalyse the fuel cell vehicles of the future.

Iridium: small but mighty

For PEM electrolysers the key metal is iridium. PEM electrolysers use iridium at the anode and platinum at the cathode, which are typically printed as catalyst-containing ‘inks’ in a thin layer applied to the proton-exchange membrane. This forms a catalyst coated membrane (CCM), which splits water into oxygen and hydrogen under an electric current, with a semi-permeable membrane that allows proton exchange. Seals are applied and the CCM is then sandwiched between gas diffusion layers to allow the gases to move to and from the active layers, forming a cell. A number of these cells connected in series then forms the heart of the electrolyser stack.

JM Proton Exchange Membrane Diagram
Diagram of the catalyst coated membrane (CCM) and PGM use within it

While platinum is targeted as one of the major products of mining operations, iridium occurs in such small quantities that nobody goes after it in its own right: it gets a free ride to the surface on the back of platinum.

Minor in quantity it may be, but iridium is a very useful industrial metal. Its electrochemical power is harnessed not just in PEM electrolysis, but also in the chlor-alkali industry, in the production of copper foil by electrodeposition, and in other applications. As a chemical catalyst, it is often used to produce acetic acid. In electronics, it is used in OLEDs and as solid iridium crucibles to ‘grow’ crystals that are used as filters in our mobile phones. But it is probably most familiar as the ignition tips in long-life spark plugs for our cars.

Currently the iridium market is balanced, in that all metal produced by the mines each year is used by these various applications (2021 was unusual: demand was still recovering from Covid, and some of the miners sold additional metal from stocks). With new applications such as PEM electrolysis expected to see growing demand, demand reduction in other areas will occur in response, through a mixture of technological innovations that allow switching to substitutes, increased efficiency and therefore thrifting, or increased recycling.

2021 Iridium Demand
Iridium demand by application in 2021

Solving the iridium challenge

So, the key question: will there be enough iridium available for PEM electrolysis capacity to grow as hoped? The answer is yes – if we maximise the efficiency with which we use the metal, and if we recycle.

To illustrate the power of these two drivers, let’s look at a theoretical case where just 1.5 tonnes per year of iridium is available to be used in PEM electrolysis (this is only around 20% of annual mined production, so a realistic assumption). How much PEM capacity could we build up within that constraint?

The impact of thrifting and recycling on PEM capacity
Projected cumulative PEM capacity with consumption limited to 1.5 tonnes of primary iridium per year, using the Hydrogen Council 1.5°C scenario

Today’s technology uses around 400 kg per gigawatt of PEM capacity, so 1.5 tonnes doesn’t buy you a lot of gigawatts. The blue lines on the chart show the impact of progressive thrifting: reduce the metal per gigawatt by 80% by 2030 and you can build 60% more capacity than if you only halve your metal requirement by 2030 (and our projection assumes continued thrifting to 2050). Add recycling to that, with an assumption that it happens in ‘closed loop’, so the iridium is retained within this industry, and we see a growth curve that gives over 2.5 times more capacity by 2050 than with thrifting alone.

In this exercise, even within an applied constraint of just 1.5 tonnes per year of primary iridium and using an ambitious scenario for hydrogen uptake, PEM can take market share of 40%, and achieve an installed capacity of over 1,000 GW by 2050 (based on the Hydrogen Council scenario and JM analysis).

There is one more thing to say about efficiency. Formulating more effective catalysts, more efficient membranes, and tuning the way they are assembled into catalyst coated membranes (CCMs) will increase overall system performance, so that not only will less iridium be used per gigawatt, but each gigawatt will be able to produce more hydrogen, boosting the efficiency of our raw materials use even more.

PGM for resilient supply chains

This is the power of the PGMs: they need only be used in small quantities to deliver a powerful technological impact. They are precious metals, and their price reflects that, but it is exactly this value that ensures they are used efficiently and are recycled. Circularity and minimised mineral intensity – or ‘reduce, reuse, recycle’ – are well known concepts in the PGM industry.

Added to that, supply chains that are based on PGMs rather than on base metals face different dynamics, e.g., from those experienced in the battery industry, and those dynamics support the use of PGMs in hydrogen technologies.

We know these aims can be achieved. Johnson Matthey has a long track record in PGM thrifting and in catalyst technology, and this know-how is being brought to bear on the components we produce for fuel cells and electrolysers. We can support our customers throughout the electrolyser product lifecycle, beyond system design and manufacture, offering deep understanding of the PGM markets, PGM supply and management, and a full recycling solution.

The hydrogen industry faces many challenges as it scales up and becomes an essential part of the energy transition, but concerns that platinum group metals are a barrier are misplaced. If we use them well, they can help to enable hydrogen energy.

About Johnson Matthey

Johnson Matthey (JM) is a 205-year-old British company that has become a global leader in sustainable technologies, with a vision to make the world cleaner and healthier, today and for future generations. Today, JM is applying its unique expertise in platinum group metals, complex chemistry, catalysis, and process engineering to catalyse the net-zero transition, and through the development of new solutions is supporting the emerging hydrogen economy. Underpinning this is its expert team of PGM market researchers and analysts, giving unique and informed insights on key issues in PGMs and how the markets are likely to develop.

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About this Featured Article

This article was selected and posted by the HTW Editorial Team. It was originally pubished in the Hydrogen Tech World magazine – an open-access, bimonthly digital publication dedicated to technologies associated with hydrogen production via water electrolysis, hydrogen transport, storage and distribution, and hydrogen application in fuel cells.

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Matjaž Matošec
Matjaž Matošec
Matjaž is a seasoned writer and communicator eager to effectively disseminate knowledge and always on the lookout for exciting stories and people willing to share their insights and first-hand experience. He is curious about all things industrial and passionate about the energy transition. He is editor-in-chief of the Hydrogen Tech World magazine, manager of the Hydrogen Tech World Conference, and research manager at Resolute Research.

All images were taken before the COVID-19 pandemic, or in compliance with social distancing.