In situ measurements of change in work function of Pt, Pd and Au surfaces during desorption of oxygen by using photoemission yield spectrometer in air

Abstract

We investigated the change in work function of Pt, Pd and Au surfaces during desorption of oxygen by using a photoemission yield spectrometer with an open counter. Oxygen coverage was formed by UV/ozone treatment, and then continuous change in work function with exposure to air was observed at various temperatures. Work function of Pt, Pd and Au surfaces decreased during desorption of oxygen, and finally returned to the initial value of untreated surfaces. Furthermore, temperature dependence on the change in work function was found. These characteristics were explained using chemical kinetics scheme. The exponential decay of work function was well reproduced by the first-order reaction rate equation, and it was confirmed that the order of rate constant, kr, is kr(Au)<kr(Pd)<kr(Pt). The activation energy was estimated to be 36, 38 and 28kJ/mol for Pt, Pd, Au, respectively.