Formic acid desorption from graphitized Ni(110)

The adsorption/desorption behavior of formic acid from a monolayer of graphite carbon on Ni(110) was studied using AES, LEED and flash desorption spectroscopy. Formic acid adsorbed at 165 K did not form multilayers of adsorbate. Instead, due to strong hydrogen-bonding interactions the formic acid formed a two-dimensional condensed phase on the surface and exhibited zero-order desorption kinetics initially for a 30-fold change in initial coverage. The zero-order desorption rate constant was k_d = 10¹⁸ exp[?68.2 kJ mol^?1/RT]s^?1, suggesting a desorption transition state with nearly full translational and rotational freedom on the surface. The desorption kinetics and the coverage limit were consistent with the formation of a surface polymer-monomer equilibrium.