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Platinum, a noble metal, is oxidised more quickly than expected under conditions that are technologically relevant. This has emerged from a study jointly conducted by the DESY NanoLab and the University of Vienna. Devices that contain platinum, such as the catalytic converters used to reduce exhaust emissions in cars, can suffer a loss in efficacy as a result of this reaction. A team led by principal author Thomas Keller, from DESY and the University of Hamburg, has published a recent study of this phenomenon in Solid State Ionics.
"Platinum is an extremely important material in technological terms," says Keller. "The conditions under which platinum undergoes oxidation have not yet been fully established. Examining those conditions is important for a large number of applications."
Scientists - Layer - Platinum - Zirconia - Crystal
The scientists studied a thin layer of platinum that had been applied to an yttria-stabilised zirconia crystal (YSZ crystal), the same combination that is used in the lambda sensor of automotive exhaust emission systems. The YSZ crystal is a so-called ion conductor, meaning that it conducts electrically charged atoms (ions), in this case oxygen ions. The vapour-deposited layer of platinum serves as an electrode. The lambda sensor measures the oxygen content of the exhaust fumes in the car and converts this into an electrical signal which in turn controls the combustion process electronically to minimize toxic exhausts.
At DESY NanoLab, the scientists applied a potential difference of about 0.1 volts to the platinum-coated YSZ crystal and heated it to around 450 degrees Celsius—conditions similar to those found in many technical devices. As a result, oxygen collected beneath the impermeable platinum film reaching pressures of up...
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