Iridium-Containing Automotive Emission Control Catalysts

Abstract

The possibility of partial replacement of rhodium by iridium in palladium–rhodium bimetallic nanoparticles acting as active sites of three-way catalysts has been studied. Pd–Ir–Rh trimetallic alloy particles were obtained by the thermolysis of a solid solution of double complex salts containing palladium and the second metal (iridium or rhodium) under reducing conditions. It has been determined that all the three metals are uniformly distributed in the bulk of the catalyst in places of location of alloy nanoparticles. The trimetallic catalyst samples are not inferior in thermal stability to the bimetallic catalyst Pd–Rh/γ-Al₂O₃, provided that iridium is incorporated into the active cluster as Ir³⁺ ions. The partial replacement of rhodium by iridium reduces the cost of the new material.