The platinum group metals, or PGMs, consist of platinum, palladium, rhodium, iridium, ruthenium and osmium. They have similar physical and chemical properties and tend to occur, in varying proportions, together in the same geological deposit. The usefulness of PGMs is determined by their unique and specific shared chemical and physical properties.
The PGM elements of the periodic table
While certain of these properties are shared by other materials, it is the particular combination of their chemical and physical properties that make the PGMs so valuable in their end-markets. PGMs have high and specific catalytic activity, possess high thermal resistance, are chemically inert and biocompatible, as well as being hard but malleable for forming into shapes.
Platinum, palladium and rhodium are used in higher-volume industrial and medical applications, while iridium and ruthenium have niche high-technology applications.
The attractive properties of the PGMs makes them all the subject of intensive ongoing research and development into novel end-uses.
The automotive sector is the leading end-user for platinum, palladium and rhodium. All three metals are used in varying proportions in autocatalysts, which form part of the automotive exhaust systems of both gasoline and diesel internal combustion engines in light-and heavy-duty vehicles, both on- and off-road. The unique properties of PGMs help convert harmful exhaust pollutant emissions to harmless compounds, improving air quality and thereby enhancing health and wellbeing. PGMs have accordingly been the main metals used in catalytic converters to date since the imposition of emission controls.
Vehicle exhaust emission controls began in the US in 1975, with the use of PGM-containing catalysts on light-duty vehicles. Subsequently, most other countries adopted similar legislation, notably Japan (1976), South Korea (1987), Mexico (1989), Europe (1993), Brazil (1994) and China (2000). Over time, emissions standards have continued to tighten globally, resulting in higher loadings of PGMs per catalyst in most instances, or else varying formulations and technologies, to ensure compliance with regulations.
Despite the recent increase in PGM prices, platinum, palladium and rhodium face little foreseeable competition in autocatalysts, although extensive substitution of one PGM for another is possible, driven by pricing and supply constraints. Several other metals act as good oxidation catalysts in other environments, but generally lack the thermal durability and resistance to poisoning necessary to survive in the harsh automotive tailpipe environment. An increasingly viable low emissions alternative to the combustion engine exists in the shape of the battery electric vehicle which requires no autocatalyst and hence utilises no PGMs.
However, fuel cell technologies are becoming increasingly prominent across many sectors, including transport, as part of the global push to improve air quality and reduce global warming.
Several of the fuel cell technologies make use of PGMs, principally platinum, ruthenium and iridium, to catalyse their processes.
Investment is an important driver of demand for PGMs, particularly platinum. Investment demand ranges from physical holdings of bullion bars and coins to complex investment vehicles, through exchange traded funds (ETFs) and the futures markets. Physical investments, along with global stocks, are treated as above-ground stocks that are not considered as an end-use as they could be either allocated or returned to the market, depending on price levels and investor strategy.
Learn more about each of the PGMs below:
Information above provided by SFA (Oxford)