Desorption Kinetics and Activation Energy for Cobalt Octaethylporphyrin from Graphite at the Phenyloctane Solution–Graphite Interface: An STM Study

Abstract

Temperature-dependent desorption rates and desorption energies are determined from a monolayer assembly at the solution–solid (SS) interface. Scanning tunneling microscopy (STM) was used to measure molecular-scale temperature-dependent desorption of cobalt(II) octaethylporphyrin (CoOEP) at the phenyloctane solution–highly ordered pyrolytic graphite (HOPG) interface. At lower temperatures, monolayer formation of metal(II) octaethylporphyrin (MOEP) on HOPG from solution was found to be completely controlled by kinetics, and the adlayer formed was stable up to 70 °C. Significant desorption of CoOEP from the HOPG surface was observed above 80 °C on a time scale of hours. CoOEP desorbs from HOPG into phenyloctane at a rate of 0.0055 ± 0.0007 min–1 at 90 °C, 0.013 ± 0.001 min–1 at 100 °C, and 0.033 ± 0.003 min–1 at 110 °C. From these temperature- and time-dependent measurements, assuming an Arrhenius rate law, the activation energy of molecular desorption at the SS interface was determined using studies solely ...