Direct Formic Acid Fuel Cell Pd Anode Catalyst Electrocatalytic Stability Difference Mechanism Studies

In the recent years, it was found that the direct formic acid fuel cell (DFAFC) has many advantages, comparing with the direct methanol fuel cell (DMFC). Pd catalyst is the frequently used anodic catalyst. Its electrocatalytic activity for formic acid oxidation is good. However, its electrocatalytic stability is bad. It is an important problem of DFAFC. Therefore, the study on the mechanism of the poor electrocatalytic stability of the Pd/C catalyst is meaningful. This thesis mainly investigated the mechanism of the poor electrocatalytic stability of the Pd/C catalyst, the effect of the different cathodic and anodic ions on the catalytic performance of the Pd/C catalyst for formic acid decomposition and the electrocatalytic performances of the Pd/C catalysts prepared with NH4F complexing reduction method for formic acid oxidation. The main investigation results of this thesis is as follows: 1 Study on electrocatalytic stability of the Pd/C anodic catalyst in DFAFCIn this chapter, the changes in the structure and the electrocatalytic performance of the Pd/C catalyst after dipping in the formic acid solution for a certain time were investigated. It was found that the relative crystallinity and the average size of the Pd particles of Pd/C catalyst are changed after dipping in formic acid solution. The electrocatalytic activity and stability of the Pd/C catalyst for formic acid oxidation are decreased. Considering that the structure and the electrocatalytic performance are not changed after dipping the Pd/C catalyst in water and the Pd/C catalyst can decompose the formic acid, it may be due to the certain dissolution of Pd in the Pd/C catalyst and the catalytic decomposition of formic acid at the Pd/C catalyst. This result may supply a new approach for exploring the reason for the poor electrocatalytic stability of the Pd/C catalyst for the formic acid oxidation. 2 Effect of adscititious ions on catalytic performance of Pd/C catalyst for formic acid decompositionIn this chapter, the effect of various cathodic and anodic ions on the catalytic performance of the Pd/C catalyst for formic acid decomposition was investigated. It was found that Cr3+,Zn2+,F-,Cl-,Br- in the adscititious ions and PMA could inhibit the catalytic action of the Pd/C catalyst for formic acid decomposition. Cd2+,Fe3+,PO43- would promote the catalytic action of the Pd/C catalyst for formic acid decomposition. While the effects of K+,Ni2+,Cu2+,Pd2+,BO33-,NO3- and PWA on the catalytic action of the Pd/C catalyst for formic acid decomposition are not large. 3 Electrocatalytic performance of Pd/C catalyst prepared with NH4F complexing reduction methodIn this chapter, the electrocatalytic performances of the Pd/C catalysts prepared with the liquid phase reduction method and NH4F complexing reduction method for formic acid oxidation were compared and investigated. It was found that the electrocatalytic performances of the Pd/C catalysts prepared with NH4F complexing reduction method for formic acid oxidation is better than that of the Pd/C catalyst prepared with the liquid phase reduction method. In addition, the Pd/C catalysts prepared with NH4F complexing reduction method could successfully inhibit formic acid decomposition.