Study On Catalytes Of Direct Formic Acid Fuel Cell

Three-dimensional nanoporous materials prepared by dealloying have the characteristics of self-support and good stability, which is the most popular method for the preparation of nanoporous materials. But single-phase solid solution or intermetallic compound are often used as pre alloy to prepare nanoporous materials with uniform composition and structure previously, limited systems greatly hinder the development of dealloying to prepare multi doped nanoporous metal catalysts. The research is about to combine metallic glass with electrochemical potentiostatic dealloying method, to fabricate Pd-based NPMs by dealloyingPd30CuxNi50-xP20(x=0,20,30,40). And the effect of metallic glasses’composition, corrosion potential, corrosion solution concentration, corrosion temperature and time on the composition and morphology of Pd based catalyst and its catalytic properties were studied, providing great theoretical guidance and practical significance to the development of the efficient and stable catalysts in direct formic acid fuel cell.First of all,the influence of metallic glasses’compositions on the composition and morphology of multicomponent Pd based catalysts is studied. In PdNiCuP amorphous system, Pd30CuxNi50-xP20(x=0,20,30,40)metallic glassy ribbons have larger degree of super-cooling and glass transition temperature, showing good glass forming ability, thus Pd30CuxNi50-xP20(x=0,20,30,40) system are used as pre-alloy, and dealloyed respectively at their critical potential(mV) to get nanoporous materials with moderate pore size, uniform composition. When the amorphous ribbons are dealloying at their critical potential, the addition of Cu is beneficial to promote the dealloying process, greatly shorten the dealloying time, and the average pore size is also gradually becoming larger; when dealloying at the specific voltage, because of different overpotentials, the degree of coarsening of the pores and ligaments are also different. For Pd3oCuxNi50-xP20 (x=20,30,40) systems,during the process of dealloying, non noble metals (Cu, Ni, P) atoms dissolve first on the surface, noble metal (Pd) atoms diffuse and aggregate, and finally form a stable core shell structure Pd@ PdNiCu.The effects of external conditions on the morphology and composition of the nanoporous materials formed by metallic glassy ribbons are studied. Once the dealloying time and temperature are fixed, the Pd3oNi50P20 and Pd30Cu40Ni10P20 ribbons are dealloyed respectively in 0.5 mol/L、1.0mol/L and 2.0mol/L H2SO4 solution.In 2.0 mol/L H2SO4 solution,the metallic glassy ribbons can not form a clear three-dimensional porous structure due to the surface passivation.And when the solution concentration and the etching time are fixed,the content of Ni and Cu elements in the NPMs is decreasing rapidly as the temperature is increased.Finally,the effects of the composition and pore size of the nanoporous catalysts on formic acid are determined after the dealloying process are confirmed.Pd30Ni50P20 metallic glassy ribbon dealloys in the same solution for different time,which can get the NPMs with the similar pore size,while the content of Ni is different.Among all the NPMs,the catalyst with least Ni shows the best catalytic performance.The catalytic potential is 340mV,and the current can reach to 5.63mA/cm2.