The influence of orientation on the electrocatalytic hydrogenation of hydroquinone chemisorbed at smooth polycrystalline platinum electrodes

Abstract

Abstract The influence of orientation on the electrocatalytic hydrogenation of hydroquinone (HQ) chemisorbed at smooth polycrystalline platinum electrodes in aqueous solutions has been investigated; experimental measurements, performed in the absence of bulk (unadsorbed) HQ, were based upon thin-layer electrochemical techniques. The extent of hydrogenation was characterized by (i) n H . the average number of hydrogen atoms reacted per chemisorbed HQ molecule, and (ii) the electrolytic charge Q ox for oxidation of chemisorbed organic which remained on the surface after the hydrogenation reaction. The measured values of n H indicate that the extent of HQ hydrogenation is (i) dependent upon the potential E Hyd at which hydrogenation was earned out, and (ii) a sensitive function of its initial adsorbed orientation; at a given E Hyd , n H is larger in the flat (η 6 ) than in the edge (2,3-η 2 ) orientation. Correlation of Q ox with n H , indicates that an appreciable fraction of partially hydrogenated species is desorbed from the surface; this fraction, which is a function of E Hyd , is larger in the 2.3-η 2 than in the η 6 orientation.