Preparation And Properties Of Pd-based Catalysts For Fuel Cell Application

Direct alcohol fuel cell（DAFC）as an efficient and clean energy conversion device is concerned.However,the poor stability of traditional Pd-based catalysts restricts its application fuel cell.To solve this problem,some nanoscale oxides have been prepared using liquid phase reduction method as supporting materials for palladium catalysts.Attention has been focused on the effect of oxides（in particle the binary oxides）on structure and catalytic properties of Pd/C catalysts.In addition,the effects of some other parameters including the type and cont On this basis,the content of metal oxide andent of oxide,and precipitation agents on the structure and catalytic properties of pd-based catalyst have been investigated.Based on these results,the correlation between structure and properties of the Pd-based catalysts bas been clarified.First of all,the effect of SnO₂ content on the structure,catalytic activity and stability of the catalys were studied.The results show that:SnO₂ can enhance the activity of pd-based catalysts.The size of Pd is minimum（4 nm）,the size distribution is most narrow and the catalyst activity and stability is the best,when Pd:SnO₂=2:1;Secondly,the structure,activity and stability of the catalyst prepared CeO₂/C as the carrier by different precipitating agents（sodium hydroxide,ammonia and urea）are showed:the urea as the homogeneous precipitation to preparation of Pd/CeO₂/C,particle size of CeO₂ is smallest.The Pd uniform distribute on the carrier and its particle size is smallest.At the same time,the catalyst has the best catalytic activity and stability;Thirdly,the influence of Ru-Sn oxide on the catalyst structure,catalytic activity and stability were studied.Results show that the proper addition of RuO₂（5 mol%）can be the formation of SnO₂-based solid solution.Not only can reduce the nano crystal grain size of Pd,but also changes the electronic structure of Pd.The catalytic activity and stability of Pd/RuO₂-SnO₂/C catalyst is better than Pd/C and Pd/SnO₂/C catalysts.Among them,Pd/RuO₂-SnO₂/C has the largest electrochemical active surface area（72 m2·g-1）and the lowest CO desorption onset potential（0.54 V）.It shows that Pd/RuO₂-SnO₂/C has the best anti-poisoning of CO;Finally,the effects of Zr-Ce oxide on Pd/C catalysts’ structure,activity and stability were studied.The results show that:CeO₂-based solid solution was formed by adding 50%ZrO₂.Electronic structure of Pd was changed by the strong interaction between Pd and solid solution.The catalytic activity and stability of the catalyst were significantly enhanced.In addition,solid solution can promote the adsorption of OH-on catalys.So as to accelerate the oxidation of striping CO,and improved stability of catalyst.