The adsorption of anionic [Pt_x(CO)_y]ⁿ⁻ clusters on an Au(111) electrode and its oxidative conversion to an atomic Pt adlayer

Fabricating platinum film can be a promising approach to remedy the high-cost and scarcity of Pt, and opens up an avenue for studying the electrochemical property of a unique Pt entity. The current report describes Pt-carbonyl cluster denoted as [Pt_x(CO)_y]ⁿ⁻ adsorbed onto an ordered Au(111) substrate from an aqueous PtCl₆²⁻ solution saturated with carbon monoxide (CO). This Pt+CO cluster was converted into CO-capped metallic Pt adlayer by exposing to O₂ and N₂. This transformation manifested in the drastic changes of the Au(111) surface structure, where the striped and honeycomb structures were converted into (√7 × √7)R19.1° and (2 × 2) - CO structures, as revealed by in situ scanning tunneling microscope (STM). The chemical composition of the Au(111)-supported Pt-carbonyl cluster was characterized by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV), which resulted in a 47/73 (Pt/CO) ratio. This Pt-carbonyl cluster was accompanied with counter cations La³⁺, indicating that it was anionic. The XPS and stripping voltammetry results indicate a [Pt₄₇(CO)₇₃]^5- cluster, whose CO molecules could be stripped off to produce an ordered smooth Pt metallic adlayer, making it possible to study the electrocatalytic properties of a well-organized Pt thin film.