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How Rhodium lost its Mojo (and how, like Austin Powers, it might get it back…)

It is not immediately obvious how to establish a link between Austin Powers and Rhodium – but I’ll try. It centres, essentially, on Austin’s mojo, which, for readers abroad, let’s call his virility, exemplified by his detachable hairy chest.

Well, Rhodium, as a market, once had a lot of mojo, but for a while now this most rare of metals has just not been its usual self.

Of course, no element has a right to be expensive or, as rhodium once was, to be the most expensive metal in the periodic table. But, then again, few metals have the history of rhodium…

In July 2008, just before the world’s most recent financial crash, Rhodium’s value on the open market reached the astronomic price of $10,000 per troy ounce. Let’s just visualise that for a moment – this was $321,500 for one kilo or, in other words, 1 kilo of rhodium in 2008 could have bought a nice one bed flat in a quiet tree-lined road in East Molesey, Surrey.

How could any metal be commercially useful or sustainable in an application at this price? Well, I suppose, subsequent history provides the answer. Not more than two and a half months after hitting the heights (following the financial crash, marked by Lehman Brothers’ bankruptcy in Sept 2008), Rhodium fell in a horribly straight line to $1000 per troy ounce ($32,150 per kilo) – sadly, not even a bedsit’s-worth.

So what is it about rhodium that made this element, until recently, more valuable than gold?

Discovered by the Old Carthusian, and priestly, scientist, William Hyde Wollaston, in 1803, we need to remind ourselves that it is both rarer in natural abundance and commercial production than gold – (Rh 0.2 parts per billion compared to Au 1 ppb and Rh 20-25mtpy versus Au 3,000mtpy).

As with a number of elements, its early history was not a predictor of its defining application. That early use was in thermocouples, capitalizing on its high melting point of 1964°C. But by the 1930s, Rhenium, with its even higher melting point of 3186°C, was beginning to replace it.

What ultimately gave Rhodium its X factor, you could say, was something rather more valuable to modern society than gold – that is to say, our wish for clean air. (And let’s not underestimate this – when I recently took a delegation of South Koreans around Hampton Court Palace opposite our office and expected a favourable comment on the grandeur and beauty, one of them simply said ‘If only we could take home your wonderful air’.)

The culprit for poor air quality in our cities was put at the door of auto-emissions, which spurred lawmakers in Brussels and Washington in the mid-1970s to create anti-pollution law. One of the steps was to ban neurotoxic Tetraethyl lead, which had been added to gasoline from the 1920s to boost octane ratings and, rather, promote catalytic converters – in which rhodium performed a function that other PGMs, Palladium and Platinum, didn’t. Rhodium was better at reducing NOx.

All catalytic converters have one simple aim – to make the unburnt emissions from internal combustion engines less toxic to the air we breathe.

If you have ever seen a de-canned converter in a yard (or perhaps on BBCs Crimewatch, where gangs routinely blow-torch off the cats from big cars like 4×4 Porsche Cayennes) you will have a picture of one in your mind – a man-made honeycomb of white zirconia ceramic, with massive surface area, onto which micron layers of platinum group elements are added as a washcoat.

To the average driver, the matter is simple – by passing the CO (carbon monoxide) engine emission  over and through this multi-surface sponge-like catacomb, as if by magic, the output to atmosphere is catalysed to safe CO2 (carbon dioxide). Result – happy driving.

Catalytic converter

Catalytic Converter, Courtesy of Eastern Catalytic (

What was not so clear to the average motorist, until recently, was the matter of NOx – the main constituent of smog – and to make a distinction between the capture of CO  and NOx. To the man in the street, the emissions from our fossil-fuel dependent power stations and our car emissions conflated in our minds – it was all about the carbon.

But then along comes VW…

All of a sudden smog was everywhere. There were, we now understood, two general types of catalytic converter – three-way (serving to capture CO, Hydrocarbons and NOx) used for petrol engine vehicles, and two-way (serving to capture just CO and Hydrocarbons) for use on diesel engine emissions.

At some point, as legal emission standards rose, and law makers attempted to further restrict the polluting effect of NOx to the atmosphere, a further generation of catalytic converters needed to be developed. These were ‘Lean NOx traps’ and ‘Selective Catalyst Reduction’ formulations (SCRs); the ‘lean NOx traps’ containing Rhodium while ‘Selective Catalyst Reduction’ formulations, with urea, do not.

With NOx emissions in the dock, the questions now being asked are – ‘Did the lean NOx traps under-perform?’, ‘Did VW simply skimp on the Rhodium?’ or can SCRs be improved?

In the smog of this issue, all I can say is that the possible answers may have a huge influence on the search for rhodium’s missing mojo.

What is not in doubt, is the likelihood of change. With US lawmakers on the warpath, everyone needs to try to be a NOx expert now. As a result, motorists are asking ‘What do I need to be environmentally friendly when I drive?’ And metal merchants are asking ‘Which catalyst formulation will benefit?’ Meanwhile, the US Environmental Protection Agency (EPA) has even suggested that VW should, by way of compensation, produce electric vehicles (EVs)  in the USA and set up a nationwide network of charging stations.

As with countless examples in the metal trade, a confluence of circumstances – not any one alone – is likely to be a big influence on this market over the coming years. In terms of influence on outcomes, the US with only 3% of Diesel cars on the road (compared to 50% in Europe) is finding it easier to take the high ground (where the air is thinner and cleaner), as they do not have so much at stake.

However, Dieselgate brought a message to the world that merely placing confidence in the law to obtain clean air was not the same as getting clean air.

Meantime, another subtext stalks the market – namely, the world’s reliance on just two countries – South Africa and Russia, both politically unstable, for more than 90% of the world’s rhodium supply.

Will all this mean that Rhodium will get its mojo back? Well, for that, we might just have to ask Austin Powers.

‘Now, where is that hairy-chest?’

Published March 2nd 2016 on