Surface diffusion of poisoning species during CO and formic acid oxidation on PtAu surface. The key role of the active site

A comparative study of the Pt and Pt/Au surface towards CO and formic acid oxidation was performed by conventional electrochemical techniques used in combination with an electrochemical flow cell (four-electrode configuration) and in-situ Fourier Transform Infrared Spectroscopy. With this purpose, a polycrystalline Pt electrode was modified by spontaneous deposition of gold atoms, achieving a gold surface coverage (θ) in the range of 0 ≤ θ ≤ 0.47. Formic acid and carbon monoxide electrooxidation on polycrystalline Pt and Au-modified Pt surfaces were studied by cyclic voltammetry, linear sweep voltammetry, chronoamperometry and in-situ FTIR techniques. The electrochemical and in-situ FTIR evidence collected for CO and FA oxidation on Pt/Au support the idea of a strongly modified Pt surface. At the Pt/Au electrode, Au operates as a barrier between surface domains, and the main observable result is the uncoupling of the catalytic activity. The free (fast) surface diffusion of reactants at a low potential, which leads to characterize Pt_pc as a “homogeneous surface” towards CO and FA oxidation, is not possible when Au is present.