Pd-Based Bimetallic and Trimetallic Catalyst for Direct Formic Acid Fuel Cells

Abstract

The annealing process effect on the activity of Pd/C, PdCu/C alloy, PdNi/C alloy, and the physical mixture of PdCu/C and PdNi/C alloys are studied. These Pd-based bimetallic catalysts are synthesized via a metal-salt reduction reaction. CV results indicate that the non-annealed Pd-based catalysts show similar surface structure and less electrochemical activity towards formic acid oxidation than the annealed samples in the following order: Pd/C < PdNi/C < physical mixture < PdCu/C, After annealing, the PdCu/C shows a surface structure change with more Pd(100) on the surface, while the physical mixture shows not only slightly more Pd (100) but also a larger Hdes peak shift indicative of a weaker Pd-adsorbate bond. Consequently, an enhanced activity towards formic acid oxidation is achieved for both annealed PdCu/C alloy and annealed physical mixture nanoparticles with the physical mixture nanoparticles showing the highest activity (i.e. increased from 1.7 to 3.2 mA/cm2 for PdCu/C alloy and from 1.2 to 3.8 mA/cm2 for the physical mixture nanoparticles). Based on our experimental results, the enhanced activity of the annealed samples is due to the combined effects of structural change and weakening of Pd-adsorbate bond.