Aerial view of queues of cars waiting at a toll station at night

Air pollution from cars could drop thanks to catalytic converters that work well when engines are relatively cold. Credit: Cui Guanghua/VCG/Getty

Technology

How to convince catalytic converters to ignore the chills

Precise arrangement of molecules helps to create a catalyst that works well even at low temperatures.

Scientists have added new metals to materials used for catalytic converters and, by controlling the placement of those metals on a molecular scale, have made catalysts that work much faster than previous versions.

The catalytic converters used in cars generally rely on three-way catalysts, so called because they break down carbon monoxide, hydrocarbons and nitrogen oxides. Only a limited number of such catalysts are available, and most don’t kick into action until they reach 250–400 ºC. This means that until the catalyst is heated by the car’s exhaust, pollutants escape unaltered — a problem that could worsen as engines become more efficient and thus stay cooler longer.

Andrew Getsoian at Ford Motor Company in Dearborn, Michigan, and his team distributed titanium dioxide or zirconium dioxide throughout an aluminium-oxide scaffolding that held molecules of a catalyst based on the metal rhodium. The team used a solvent to control the arrangement of the molecules. This produced a catalyst that started working at temperatures as much as 150 ºC lower than those needed for existing technology.

The researchers say that this work will improve the performance of current catalytic converters and create new possibilities for future designs.