(221g) The Effect of Two Different Preparation Method of Cu@Pd/C in Direct Formic Acid Fuel Cell

DFAFCs use anode catalysts based on precious metals such Pd. Unfortunately, palladium has poor stability, and it can be poisoned easily by carboxy species like C(OH)₂. The catalyst poisoning leads to poor stability and efficiency of DFAFC. Therefore, it is important to develop catalysts that are used in the anode of DFAFC. By using the core-shell structure of non-expensive 3d transition metals as core and the Pd as the shell, an electronic structure like the d-band center can be modified by charge transfer effects; additionally, the selectivity and activity will be altered. This lead to changes in adsorption energy of intermediate species during the electro-oxidation of formic acid on Pd surfaces. Because of using these 3d transition metals as a core and Pd as a shell in our core-shell structures, the bond energy between Pd and the intermediate formed in the formic acid electro-oxidation can be formulated with optimum bonds, which is strong enough to cause adsorption not too strong to produce poisoning species.

The studies on the core-shell bimetallic catalysts have resulted in better fuel cell performances, and different electronic properties correspond to pure Pd. Among the Core-shell structure bimetallic catalysts Cu@Pd showed the better performance. However, there are lots of preparation methods to produce the Cu@Pd core-shell catalysts, and no one has compared them yet. In the present study, Cu@Pd/C were prepared by two different methods. Core-shell and skeleton structures of Cu@Pd/C nanoparticle samples were prepared with the average size of the 6.34± 0.74 nm and 6.17± 0.31 nm, respectively. XPS data illustrate that the Pd 3d_5/2 shifts positively to higher binding energy, and the d-band center moves away from the Fermi level. Changing in the BE and d-band center shows that the electronic structure of the surfaces were modified which resulted in higher activity and stability than the Pd/C toward the FAO.