In an example of a method for suppressing aging of platinum group metal (PGM) particles in a catalytic converter, PGM particles are applied to a support. A surface of the PGM particles is passivated by exposing the PGM particles to carbon monoxide at a temperature equal to or less than 200° C. to introduce —CO groups to the surface. Atomic layer deposition (ALD) is performed to selectively grow a barrier on the support around the PGM particles.