Coverage-dependent acrylonitrile adsorption and electrochemical reduction kinetics on Pb electrode

Electrochemical dimerization of acrylonitrile (AN) is an environmentally friendly approach to manufacture adiponitrile (ADN), the key raw material of nylon-6,6. Despite its significance in industry, the studies on the mechanism and kinetics of AN conversion on cathode are relatively limited. Herein we investigated the adsorption and electrochemical reduction of AN on Pb electrode under different coverage by the combination of experiments and density function theory (DFT) calculations. Under various reaction conditions, it was observed that when decreasing the bulk concentration of AN, the generation of ADN decreases as expected while that of the saturated propionitrile (PN) increases on the contrary, indicating a coverage-dependent kinetic behavior. Theoretical analysis revealed high AN coverage on Pb surface could inhibit the formation of H and repel the contacting of C=C with active site, both of which is against the generation PN and favorable for ADN. A kinetic model was then developed for the cathodic reaction by taking the impact of temperature, potential and surface coverage into account, which gives good agreement in a wide range of operation conditions.