Electrochemically induced oxygen spillover and diffusion on Pt(111): PEEM imaging and kinetic modelling

Abstract

Electrochemically induced oxygen spillover and diffusion in the Pt(O₂)|YSZ system is investigated in a combined experimental and theoretical study. The spreading of spillover oxygen is imaged by photoelectron emission microscopy (PEEM) on dense and epitaxial Pt(111) thin film electrodes prepared by pulsed laser deposition (PLD). Two different models are used to obtain surface diffusion coefficients from the experimental data, (i) an analytical solution of Fick's 2nd law of diffusion, and (ii) a numerical reaction-diffusion model that includes recombinative desorption of O₂ into the gas phase. The resulting diffusion coefficient has an activation energy of 50 kJ mol⁻¹ and a preexponential factor of 0.129 cm² s⁻¹ with an estimated uncertainty of ±20% for the activation energy and ±50% for the absolute value. The Fickian model slightly overpredicts diffusion coefficients due to the neglect of oxygen desorption. Experimental and theoretical results and limitations are discussed and compared to previous work.