A 3-DIMENSIONAL POTENTIAL-ENERGY SURFACE FOR DISSOCIATIVE ADSORPTION AND ASSOCIATIVE DESORPTION AT METAL-ELECTRODES

A simple model is constructed to calculate the potential-energy surfac e of dissociative adsorption and associative desorption reactions at t he metal/solution interface; The model is based on an extension of the Anderson-Newns Hamiltonian and has three reaction coordinates; the bo nd length or the distance between the fragments, the distance from the surface; and-the generalized solvent coordinate familiar from the cla ssical, theory of electron-transfer reactions. The properties of the t hree-dimensional potential energy surfaces are studied and the activat ion energy for dissociative adsorption is calculated as a function of the applied potential and the metal-work function, In the observed tre nds, the absorption energy and hence the electrosorption valency of th e fragments play an important role. For certain ''extreme'' values of the bonding or antibonding energy levels, molecular ions may become me tastable and affect the reaction mechanism. (C) 1998 American Institut e of Physics.