Electrochemical Reduction of Formic Acid on a Copper-Tin-Lead Cathode

The electrochemical reduction of formic acid in acidic solution (2 mol L -1 HCl) on a Cu(88)Sn(6)Pb(6) cathode was studied. The main products of the reduction were methanol and ethanol having %Current Efficiencies (CEs) of 30.3 and 37.6% respectively at -0.8 V vs Ag/AgCl. Small amounts of methane and ethane were also detected. The rate of the reduction increased exponentially with the negative potential in the range -0.65 to -1.00 V and the maximum of the %CE was observed at -0.8 V. The rate of the reduction of HCOOH increased slightly with the concentration of HCOOH. In pure HCOOH as electrolyte a noticeable amount of CH3CHO (17.1%) was detected. A possible reduction mechanism was proposed in which the adsorbed CO is the key intermediate for the formation of all the products.