Platinum is a key precious metal used inside automotive catalytic converters to speed chemical reactions that convert toxic exhaust gases into less harmful ones, especially oxidizing carbon monoxide and hydrocarbons and helping split nitrogen oxides[2][4].
Why platinum is used and what it does
– Platinum acts as a catalyst: it provides active surface sites where exhaust molecules can adsorb and react without the metal itself being consumed[2][4].
– In three-way converters (the common type on modern gasoline cars) platinum promotes oxidation reactions that turn carbon monoxide to carbon dioxide and hydrocarbons to carbon dioxide and water[2][4].
– Platinum is chemically robust: it tolerates very high temperatures, resists corrosion and poisoning better than many alternatives, and endures the harsh environment inside the exhaust stream[4].
Where platinum sits in the converter
– The converter contains a honeycomb or cellular ceramic substrate whose many channels are coated with a washcoat that holds dispersed platinum (and often palladium and rhodium) as nanoparticles, maximizing surface area for reactions[2][4].
– Converters are typically positioned to reach and maintain high operating temperatures (often several hundred degrees Celsius) so the platinum sites remain active[1][2].
How platinum interacts with other precious metals
– Platinum is usually paired with palladium and rhodium because each metal excels at different reactions: platinum and palladium are effective for oxidation of CO and hydrocarbons, while rhodium is especially good at reducing nitrogen oxides[4].
– Automakers balance the mix of these platinum group metals to meet emissions targets and to manage cost and availability[4].
Practical impacts and trends
– Because platinum and other PGMs are valuable and concentrated in a small physical volume, catalytic converters are frequently targeted for theft and are recycled when vehicles are scrapped[1][2][4].
– Market forces and emissions regulations influence which PGMs are used; shifts between platinum and palladium usage have occurred as prices and supply have changed, and future technologies (for example hydrogen fuel systems) may continue to rely on platinum for catalytic roles[4].
Common misconceptions
– The converter does not “burn” pollutants; it converts them via surface-catalyzed chemical reactions facilitated by metals like platinum[2].
– Not all converters contain the same amounts of platinum; composition varies by vehicle type, engine, model year and regional emissions standards[2][4].
Sources
https://www.autoexpress.co.uk/car-news/108937/what-is-a-catalytic-converter
https://pmrcc.com/en/news-blog/catalytic-converter-101/catalytic-converter-value/
https://www.youtube.com/watch?v=qytqlqDvJ-k
https://iscrapapp.com/blog/how-catalytic-converters-reduce-pollution/