Towards a Mechanistic Understanding of Platinum Thin Film Deposition on Au(111)

Pt group metals and alloys thereof have important application as magnetic thin film materials and catalysts for fuel cell applications. The production of ultrathin Pt group metals thin films currently relies on surface-limited place-exchange, requiring the time-consuming exchange of electrolyte, and resulting in films with a possibility of metallic impurities. A new method was recently reported for the production of thin films through the use of large overpotential deposition of Pt on Au(111) using Pt(II) electrolytes with a high halide concentration. Under these conditions, two-dimensional islands form, and three-dimensional growth is inhibited. The mechanisms of this two-dimensional deposition and the self-termination are not completely understood, although experimental evidence suggests that the self-termination is due to underpotential deposited hydrogen blocking the surface of the newly-formed platinum film, preventing additional layers from growing. We use computational techniques coupled with electrochemical experiments to probe the reaction pathway and associated barriers to gain more insight into the growth process and its extendability to other metals.