Platinum Monolayer Electrocatalysts: Tunable Activity, Stability, and Self-Healing Properties

Platinum monolayer-nanostructured electrocatalysts were developed principally for the oxygen reduction reaction starting with fundamental studies on single-crystal substrates, supported by theoretical treatments, synthesizing nanoparticles, followed by scale-up syntheses and fuel cell tests. These catalysts consist of nanometer-scale core-shell particles with monolayers of platinum that are supported by metal, metal alloy, or nanostructured noble metal/non-noble metal cores. In addition to an ultralow Pt content (one monolayer) and high Pt utilization (all atoms are on the surface and can participate in the reaction), these catalysts are characterized by very high activity and stability induced by supporting nanoparticles cores, by the ability to tune the catalytic activity of a Pt monolayer depending on the properties of the top atomic layer of the cores, and by a self-healing property. The latter two properties, which open particularly broad possibilities for applications of these catalysts, will be briefly analyzed in this article. Examples of tunable activity include electrocatalysts consisting of a Pt monolayer on smooth core surfaces, Pd tetrahedral nanoparticles, Pd nanowire, and hollow Pd nanoparticle cores. The self-healing properties are illustrated by stability tests involving potential cycling. Possible future research involving these catalysts is discussed.