Carbon supported palladium-copper bimetallic catalysts for promoting electrochemical oxidation of formic acid and its utilization in direct formic acid fuel cells

Carbon supported palladium-copper (Pd-Cu) bimetallic catalysts (Pd_xCu_y/Cs) are fabricated by modified polyol method to enhance the reaction rate of formic acid oxidation reaction (FAOR) and the performance of direct formic acid fuel cell (DFAFC) through weakening the bond with the intermediate of formic acid. According to the evaluations, when the ratio of Pd and Cu is 3 : 1 (Pd₃Cu₁/C), catalytic activity is best. Its maximum current density is 1.68-times better than that of commercial Pd/C. Even from the optical and spectroscopic characterizations, such as TEM, EDS, XPS and XRD, Pd₃Cu₁/C shows an optimal particle size and a higher degree of alloying. This is because in Pd₃Cu₁/C catalyst, the d-band center that induces the weakening in adsorption of formate anion groups to Pd surface is most positively shifted, and this positive shift promotes the reaction rate of FAOR, which is the rate determining step. When the performance of DFAFCs using the Pd_xCu_y/C catalysts is measured, the maximum power density (MPD) of DFAFC using Pd₃Cu₁/C catalyst is 158 mW cm⁻², and this is the best MPD compared to that of DFAFCs using other Pd_xCu_y/C catalysts. In addition, in a comparison with commercial Pd/C catalyst, when the same amount of catalyst is loaded, MPD of DFAFC using Pd₃Cu₁/C catalyst is 22.5% higher than that of DFAFC using commercial Pd/C.