| An electrogenerative technique, involving the reduction of CO(,2), has been investigated for the synthesis of formic acid, formaldehyde and methanol. Such synthetic fuels are considered as possible alternates to the use of petroleum-based fuels. The electrogenerative reduction of carbon dioxide on catalytic electrodes Pt and Pt-Sn is accomplished with significantly lower energy requirements relative to the conventional electrochemical reduction. In addition, because of the different potential regions at which electrocatalytic reduction of CO(,2) occurs, and since the major product formed depends on the potential, the possibility exists to form certain products selectively using electrocatalytic reduction.;Electrocatalytic reduction of carbon dioxide has been investigated at standard pressure (1 atm), and room temperature (25(DEGREES)C) in a three-compartment all-Teflon electrochemical cell. The effects of this type of electrocatalyst (Pt, Pt-Sn) and operating conditions, specifically the cathode potential, the electrode and carbon dioxide concentration, on the reaction rate and product selectivities have been examined. At the optimal potential (0.05 V vs reversible hydrogen electrode) platinum and platinum-tin (11%) yield the same activity for the formation of methanol. However, platinum-tin (11%) was more selective than platinum in the formation of formic acid. The formation of formic acid improves with decreasing hydronium ion concentration of the electrolyte.;After a 3 hour run, the total yields of HCOOH and CH(,3)OH are very low under the conditions used in this work. Hence this process needs to be further developed; only slightly depends on the pH.;Particular attention was paid to the poisoning effect of the chemisorbed intermediates formed in the adsorption of carbon dioxide on plantinum. The accumulation of a poisoning residue on the plantinum surface leads to a large drop in a catalytic activity. The presence of a submonolayer of Sn adatoms on the plantinum surface decreases the probability of forming the poisoning species and enhances the catalytic activity for reduction reactions. Reproducible platinum-tin electrocatalysts with the desired composition have been prepared by underpotential deposition of tin on platinum from 2N HC10(,4) + SnSO(,4) solutions. |
