Improve The Direct Formic Acid Fuel Cell Anode Pd Catalyst Performance Approach And Mechanism

In recent years, formic acid is paid much attention to because of its characteristics of non-toxic, non-flammable, safe, high energy density and so on. Therefore, direct formic acid fuel cell (DFAFC) has much more advantages than that of direct methanol fuel cell (DMFC) and has a very good application prospects. In DFAFC, the electrocatalytic activity of the Pd anodic catalyst for the oxidation of formic acid is better than that of the Pt catalyst. However, its electrocatalytic stability is poor. Thus, it is significant to investigate the improving the electrocatalytic stability of the Pd catalyst and its mechanism. Meanwhile, exploring the method of increasing the electrocatalytic activity and stability of the Pd catalyst is very necessary. In this thesis, the effect of anions and cations on the surface of Pd nanoparticles as well as the effect of the alloy with different atomic ratio on the electrocatalytic performance of the Pd/C catalyst electrode for formic acid oxidation and its mechanism were investigated. The main results of the thesis are as follows:1. The investigation of the influence and mechanism of the electrocatalytic performance of the catalyst with different atomic ratio Pd-Au alloy for formic acid oxidationIn this chapter, the Pd-Au alloy catalyst with different atomic ratio, Pd/C and Au/C catalyst by liquid phase reduction method. It was found that no matter what the proportion of Pd-Au alloy catalyst, their electrocatalytic activity and stability are better than that of Pd/C catalyst. Besides Pd and Au form the alloy could decrease in Pd dissolution, it is related to the strong resistance to poison and the obvious inhibition to self-decomposition of formic acid. However, the electrocatalytic performance of Pd-Au alloys with different Pd and Au atomic ratios are also different. The sutable addition of Au would obtain the best electrocatalytic performance of the catalyst for the oxidation of formic acid. When the Pd-Au/C catalyst with7.5:1atom ratio of Pd and Au it possesses the best electrocatalytic performance for formic acid oxidation.2. The electrocatalytic performance of the Pd/C catalyst prepared with THF complex reduction method for formic acid oxidationIn this chapter, the Pd/C catalyst is prepared with THF complex reduction method. In addition, the particle size, morphology and structure of the catalyst are analyzed with various methods. The study showed that the electrocatalytic performance of Pd/C-T catalyst is much better than that of Pd/C catalyst. The good dispersibility of Pd particles, the strong antitoxic ability of CO and the weak catalytic performance for self-decomposition of formic acid are the reasons for the good electrocatalytic performance.3. Promoting action of Pd2+adsorbed on the surface of Pd/C catalyst on the electrocatalytic performance for formic acid oxidationIn this chapter, the electrocatalytic activity and stability of the Pd/C catalyst and after immersing the Pd/C catalyst in Pd2+solution for the oxidation of formic acid were compared. It was found that some Pd is indeed dissolved in the solution of0.5mol/L H2SO4and0.5mol/L HCOOH. The electrocatalytic performance of the Pd/C catalyst after immersing in Pd2+solution for formic acid oxidation is increased. The reasons are as follows:(1) The Pd2+ionswould effectively inhibit the Pd dissolution.(2) The Pd2+ions adsorbed on thePd nanoparticles could increase in the surface roughness.(3) Pd2+ions on the surface of Pd particles can make the intermediate of formic acid oxidation easy to be oxidized to CO2.(4) Pd2+could be reduced to Pd between-0.2V and0.8V electrode potential. Then, the new active sites are generated and Passivation would be decreased4. The high electrocatalytic performance of the Pd/C catalyst adsorbed AlF63-for the oxidation of formic acidIn this chapter, a new Pd/C catalyst was prepared by the adsorption of AlF63-and the complexation method of tetrahydrofuran (THF). It was found that AlF63-anions are indeed adsorbed on Pd nanoparticles, but there is no THF molecule. Under the solvation effect and action of adsorbed AlF63-, the electrocatalytic performance of the new Pd/C catalyst is much better than ordinary Pd/C catalyst for formic acid oxidation. Because the new Pd/C catalyst owns the high content of PdⅡ, the good dispersibility of Pd nanoparticles, the stronger resistance to CO, the obvious inhibition for self-decomposition of formic acid, and so on.