Direct formic acid fuel cell (DFAFC) has been a hot area of research for recent years due to its advantages, such as high energy density, safe and non-toxic, convenient transportation and so on. In DFAFC, the electrocatalytic activity of the Pd anodic catalyst for formic acid electro-oxidation is much better than that of the Pt catalyst. However, its poor electrocatalytic stability is the primary factor, which restricts its commercial road. Thus, it is significant to improve the electrocatalytic stability of the Pd anodic catalyst. In this thesis, the effect of different supporters on the electrocatalytic performances of the Pd based catalysts for formic acid electro-oxidation were investigated from the two sides, Firstly, the electrocatalytic activity and stability of the catalysts prepared, Secondly, the decomposition of formic acid. The investigation results of this thesis are as follows:1. The electrocatalytic performance of carbon supported Pd catalyst modified with Keggin type of Sn-substituted polyoxometalatate for formic acid electro-oxidizationThe Pd/C catalyst is modified with Keggin type of Sn-substituted polyoxometalatate K7Coâ…¡W11O39Snâ…£OH by the water bath at the room temperature and the resulting catalyst is designated as Pd/C-K7catalyst. It was found that electrocatalytic activity and stability for formic acid electro-oxidation of the Pd/C-K7catalyst are largely improved. The reasons may be as follows:(1) K7Coâ…¡W11O39Snâ…£OH adsorbed on the catalyst can occupy the surface active sites of the Pd atom and reduce the amount of COads.(2) The adsorbed CoIIW11O39Snâ…£OH anion facilitates the electro-oxidation of poisoning species, such as COads or the CO-like species.(3) The Pd/C-K7catalyst can effectively inhibit the decomposition of formic acid. Thus, the poisoning effect is slow down.2. The electrocatalytic performance of the insoluble polyoxometalatate TBA7Coâ…¡W11O39Snâ…£OH supported Pd catalyst for formic acid electro-oxidizationThe insoluble polyoxometalatate TBA7Coâ…¡W11O39Snâ…£OH is used as the carrier and the Pd/TBA7catalyst is synthesized with a simple impregnation-reduction method. It was found that the electrocatalytic activity and stability of the Pd/TBA7catalyst for formic acid electro-oxidation are much better than that of the Pd/C catalyst. It is due to the strong interaction between Pd and TBA7Coâ…¡W11O39Snâ…£OH, leading that the Pd/TBA7catalyst not only possesses a much higher tolerance toward COads poisoning but also inhibits the decomposition of formic acid. Thus, the poisoning effect is slow down. 3. The electrocatalytic performance of the Pd catalyst with the mixed supporters of h-BN and C for formic acid electro-oxidizationThe Pd caytalysts with the mixed supporters of h-BN and C with different weight ratios, such as Pd/BNã€Pd/(BN)2C1ã€Pd/(BN)1C2and Pd/C are synthesized with the simple impregnation-reduction method. It was found that the weight ratio of h-BN and C could affect the electrocatalytic performances of the Pd based catalysts. When the weight ratio of h-BN and C is2, the electrocatalytic activity and stability of the Pd/(BN)2C1catalyst are the best in all of Pd based catalysts. It is due to that h-BN and C have respective advantages. If the content of C is too high, the contact area of h-BN and Pd is small, leading that mutual action becomes small. When the content of C is too low, the resistance of the catalyst would be increased and the electrocatalytic performance would be decreased. Only when the weight ratio of h-BN and C is suitable, the electrocatalytic activity and stability would be best.
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