Study Of Pd-based Multi-Component Composite Catalyst For Direct Formic Acid Fuel Cell

Direct formic acid fuel cell has attracted extentsive attention due to its advantages of non-toxic,low permeability and so on.Catalysts are very important for the development of fuel cells.Generally,Pt-based catalysts and Pd-based catalysts are commonly used as anode catalysts for formic acid oxidation.In fact,extensive studies have been shown that Pd-based catalysts are more suitable for formic acid oxidation anode catalysts when compared with Pt-based catalysts.However,further studies indicate that Pd catalysts had the disadvantage of low catalytic stability.Therefore,improving the performance of Pd catalysts has become a hot topic in the research filed of direct formic acid fuel cells.It is well known that the performance of the catalyst is affected by its composition and morphology.In recent years,a large number of studies have shown that introduction of base metal elements to Pd catalyst and the control of the morphology and structure of the catalyst can effectively improve the performance of the catalyst.Therefore,in this thesis,from the aspect of catalyst cost and stability,we studied the influence of base metal Sn,Cu and morphology and structure on the performance of catalyst.The major findings of this thesis are summarized below:（1）PdSn/TiC catalysts with different ratio were prepared by impregnation reduction method.The effect of metal Sn on the performance of Pd catalyst was investigated.Meanwhile,the optimum proportion and possible catalytic mechanism of PdSn/TiC catalyst were discussed.Results have suggested that the introduction of metal Sn can improve the dispersity of the catalyst,and the synergistic effect and the electronic effect between Pd and Sn can improve the activity and stability of the catalyst efficiently.It also found that the presence of SnO_x can enhance the toxicity of the catalyst.（2）On the basis of PdSn binary catalyst,the third kinds of metal Cu was added,and different proportion of PdSnCu/TiC catalysts were prepared.The catalytic performance of catalyst for formic acid oxidation was studied.Studies have showed that the catalytic activities,stability and CO tolerance ability were further enhanced by the addition of Cu,and the catalytic performance of Pd₂Sn₁Cu₁/TiC catalyst was the best.This is mainly because Cu or CuO_x can decompose H₂O at low potential to produce hydroxyl group and induce the CO translate to CO₂ on the surface of the catalyst,which weakens the CO poisoning phenomenon and improves the performance of the catalyst.（3）At room temperature,PdSn nanosponge（PdSn NSs）catalysts with different ratios were prepared via liquid phase reduction method using NaBH₄ as reducing agent.The results showed that PdSn NSs catalysts had better activity and stability when compared to PdSn/TiC.This may be because the porous structure of PdSn NSs increases the specific surface area of the catalyst,thereby improving the activity of the catalyst.While the improvement of catalyst stability can be ascribed to the two aspects:on the one hand,PdSn NSs has a special porous structure;on the other hand,PdSn NSs dose not required support,which can avoid the adverse effects brought by the support.