Electrochemical reduction of CO2 and oxidation of adsorbed species on the rhodium electrode

Abstract

The adsorption of CO 2 on the rhodium electrode and the oxidation of the adsorption products were investigated by the use of a radiochemical method, by cyclic voltammetry and by chronoamperometry. The adsorption process occurs in the hydrogen region and the oxidation of the resulting organic species takes place in the oxygen region of the electrode potentials, respectively. Making use of the charges involved in the hydrogen asorption and in the oxidation of the organic adsorbate, the net composition of the CO 2 adsorption products was found to be best represented (for E ads >0.000 V) by the carbon atom bonded to four adsorption sites. It was also found that a surface oxidant is needed for the r.d.s. of the oxidation process. This report refers to some earlier works concerning the interactions of CO 2 with noble metal surfaces. In particular it is shown that the CO 2 adsorption probably does not pass through the activated CO 2 intermediates which are weakly bonded to the bare Rh sites. It is more likely that two Rh-H sites and the CO 2 molecule from the bulk of solution are involved in the adsorption mechanism (r.d.s.)