Electrochemical CO2 Reduction on Pd-based Bimetallic Catalysts Ruud Kortlever, Ines Peters, Collin Balemans, Youngkook Kwon, Marc T.M. Koper Catalysis and Surface Science, Leiden Institute of Chemistry, Leiden University PO Box 9502, 3200 RA Leiden, The Netherlands e-mail address: [email protected] The electrochemical reduction of CO2 has become a widely studied reaction in recent years. It has the potential of closing the anthropogenic carbon cycle by converting CO 2 with renewable energy to fuels.[1] The utilization of CO2 by electroreduction to fuels could not only have the advantage of replacing fossil fuel-based energy sources, but could also lower CO2 concentrations in the atmosphere. However, at the moment the main problems that inhibit electrochemical CO2 reduction from being applied are the high overpotentials that are needed and the poor product selectivity. Therefore, a key challenge in present research is the development of catalysts that efficiently and selectively reduce CO2 to useful products. In our present work, we have been using the ‘reversible catalyst principle’ as inspiration to design an electrochemical catalyst that is able to reduce CO 2 to formic acid at low potentials. This implicates that materials that are active for the oxidation of formic acid to CO2 were tested for the reverse reaction. Since formic acid oxidation catalysts mainly consist of platinum and palladium[2] we have made a catalyst by making (mono-)layers of palladium on a platinum substrate. These catalysts show a very low onset potential of -0.05 V vs. RHE for the reduction of CO2 to formic acid in a pH 7 electrolyte. Furthermore, since the catalyst is also active for the oxidation of formic acid, reversible electrocatalysis is possible with this catalyst. When palladium (mono-)layers were deposited on a gold substrate different catalytic behaviour was observed. This type of catalyst is able to produce hydrocarbons ranging from methane (C1) to C4-species from CO2 starting from a potential of -0.8 V vs. RHE. This is especially remarkable since bulk gold is not able to reduce CO 2 to hydrocarbons and bulk palladium is only able to make methane and ethylene at higher potentials (>-1.2 V vs. RHE.). References [1] M. Gattrell, N. Gupta, A. Co, Energy Convers. Manage. 48 (2007) 12551265. [2] X. Yu, P.G. Pickup, J. Power Sources 182 (2008) 124-132. ise140239 j / mA cm -2 6 4 2 + 2 e+ 2 H+ 0 - 2 e- -2 - 2 H+ -4 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 E (V) vs. RHE Fig. 1: Cyclic voltammogram of reversible CO2 reduction and formic acid oxidation on a Pd@Pt electrode in a pH 7 electrolyte in the presence of CO2 and formic acid.