Preparation And Properties Of Pd-based Catalysts Of Fuel Cell With High Stability

Direct ethanol fuel cells(DEFCs)have attracted much attention recently due to it's extensive sources,clean and less pollution in burning,and also easy to store.These advantages make DEFCs have great significance in solving the energy problem and environmental pollution problems.Catalyst is an important part of fuel cells and also determines the efficiency of fuel cells.But during the process of ethanol electrooxidation,the process of ethanol completely electrooxidation into carbon dioxide is complex,including the dissociation of C-C,the adsorption of intermediate products and so on.The noxious intermediate products will cause catalyst poisoning by adsorption on the catalyst surface,thereby limiting the commercial application of DEFCs.Developing highly efficient and stable catalyst materials is an effective way to promote the application of DEFCs.In this paper,in order to solve the problem of poor stability,high usage of noble metal and high cost of Pd-based catalysts,we have provided several solutions and analyzed the mechanism systematically.Finally,We have obtained the following results:Firstly,we used the hydrothermal carbonization(HTC)technique to modify carbon nanotubes and then used modified carbon nanotubes as carrier to prepare the catalyst Pd/HTC-CNT,also analyzed the introducing HTC technique in carrier material and it's influence on the structure of catalyst and the catalytic activity and stability in ethanol electrooxidation.The results showed that the carrier material of carbon nanotube modified by HTC technique not only help the decrease of formed Pd particles,but also improve the dispersion on the carrier surface and the content of metallic Pd.Therefore,the catalyst Pd/HTC-CNT has the higher electrochemical activity area accordingly shows greater catalytic activity and stability in ethanol electrooxidation.Secondly,we used N-doped carbon nanotubes modified by HTC technique as carrier material to prepare the catalyst Pd/HTC-N1.67%CNT,also analyzed the introduced N element in carrier and it's influence on the structure of catalyst and the catalytic activity and stability in ethanol electrooxidation.The results showed that the interaction between N and Pd facilitates the formation of metallic Pd.On the other hand,the introducing of N provides a number of defects on the surface of NCNTs to help anchoring metallic Pd.Therefore,the catalyst Pd/HTC-N1.67%CNT has the highest electrochemical activity area accordingly shows greatest catalytic activity and stability in ethanol electrooxidation.Thirdly,we used N-doped modified carbon nanotubes as carrier materials and liquid phase reduction method to prepare the PdSn alloy catalyst PdSn/HTC-NCNT.,also analyze the introducing Sn element in alloy catalyst and it's influence on the structure of catalyst and the catalytic activity and stability in ethanol electrooxidation.The results showed that the interaction between N,Sn and Pd facilitates the formation of metallic Pd which is because Sn has low electronegativity compared to Pd.Therefore,the catalyst PdSn/HTC-NCNT catalyst has the highest electrochemical activity area accordingly shows greatest catalytic activity and stability in ethanol electrooxidation.On the other hand,the existence of Sn and its oxides play an important role in the electrooxidation of small organic molecules which can promote the adsorption of oxygen species,remove noxious intermediates and improve the stability of the catalyst.Therefore,The catalyst PdSn/HTC-NCNT shows the best catalytic activity and stability.