Platinum oxidation state for catalytic converters

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Category: Emissions Control

Subject: Platinum oxidation state for catalytic converters

Question

What is the oxidation state of platinum used as catalyst in catalytic converters? Is the platinum zerovalent or used as an oxide or any other type of compound?

Answer

The preparative route is designed to ensure that the platinum precursor is converted to highly dispersed metallic particles. Analytical techniques, such as X-ray photoelectron spectroscopy (XPS) or temperature-programmed reduction, often show some residual oxidised platinum in freshly prepared catalysts. However, the oxide is confined to the surface of the metal particles, and can be readily removed (e.g. just by exposure to operating conditions).

Answer posted 08 August 2007

Submitted by: Mr Jaime Werner

Answered by: Dr Stan Golunski

Affiliation: Technology Manager of Gas Phase Catalysis, Johnson Matthey Technology Centre