Electro-catalytic reduction of ethylene on platinum and ruthenium

Abstract

The kinetics of the cathodic reduction of ethylene on platinum and ruthenium in aqueous acid and alkali solutions are reported. The reduction proceeds according to the stoichiometric equations C₂H₄+ 2H⁺+ 2e → C₂H₆(acid), or C₂H₄+ 2H₂O + 2e → C₂H₆+ 2OH^–(alkali). Tafel slopes, reaction orders in hydrogen ion and ethylene together with temperature effects have been determined by steady state potentiostatic techniques combined with chromatographic analysis. Two types of limiting current were observed under different conditions (i) a limiting diffusion current and (ii) a reaction limiting current associated with ethylene desorption from the electrode which leads to a maximum in the (potential-current) plots. Steady state parameters taken in conjunction with coverage measurements obtained from linear anodic sweeps indicate that the overall rate of reaction is controlled by the step C₂H₄(ads)+ H(ads)→ C₂H₅(ads)