Synthesis And Properties Of Pt/Pd Nanomaterials As Electrocatalysts For Alcohols Oxidation Reaction

The catalysts for electrocatalytic oxidation of alcohols have some problems to be solved,such as poor catalytic activity,durability,CO resistance,and high cost.The key to solving these problems lies in the effective regulation of the specific surface area and surface structure characteristics of catalysts,that is,the multi-factors synergistically enhance the comprehensive performance of the catalysts through the nano-size geometry as well as the diversity of surface components and structures.In the present work,Pt/Pd-based nanomaterials were synthesized through different methods,and their surface compositions and structures were designed and regulated.The electrocatalytic properties of alcohols oxidation reactions were analyzed,and the correlations between geometric size,surface composition,structural characteristics,and performance of the catalysts were investigated to find out the influence mechanism.NiPtAu hollow nanocrystals were prepared by chemical replacement method,and the contents,distribution characteristics,and catalytic performance of Au on the surface were analyzed.It is found that the introduction of non-catalytic active component Au and its surface content and distribution have important effects on the performance.The specific activity(31.52 m A cm^-2)and mass activity(1184.64 m A mg _Pt^-1)of the Ni PtAu catalyst with Au content of 15.17 at.%were about 7.0 and 1.6 times of those of commercial Pt/C,respectively.Additionally,the onset potential（-0.65 V）and peak potential（-0.38 V）of CO oxidation of this catalyst are lower than those of commercial Pt/C,and its stability does not degrade significantly after pumping the CO,showing excellent CO resistance.The theoretical calculation confirms that the introduced Au can weaken the adsorption of CO at the Ptsurface and inhibit the toxic effect of CO,so as to improve the anti-CO toxicity performance and working actual effect.Pd nanoparticles supported on carbon black were fabricated by solid-phase transient thermal shock,the structural characteristics,formation conditions,and influence on the catalytic performance of twin boundaries and atomic steps constructed on the nanoparticles surface were analyzed.The results show that the surface defects generated on the Pd nanoparticles under the extreme non-equilibrium conditions are greatly beneficial to improve the catalytic performance,the specific activity(3.22 m A cm^-2)and mass activity(1846.00 m A mg^-1)reach 4.6 and 6.4 times higher than those of commercial Pd/C,respectively.It also displays excellent long-term cycle stability（85.0%activity retention after 900 cycles）and CO tolerance.The theoretical calculation results further reveals that the twin boundaries promote the separation of CO and OH at the optimal adsorption sites on the Pd surface,resulting in uneven adsorption,which can reduce the severity of the active site poisoning and significantly improve the electrocatalytic performance.Ketjen black supported Ptsingle atoms-clusters materials were manufactured by air-assisted low-temperature thermal shock,and their structural characteristics,morphology formation mechanism,and performance were analyzed.It is found that the carbon defects and surface oxygen hinder the thermal migration and agglomeration of Ptatoms during the synthesis process,resulting in fine and uniform Ptnanoparticles,and the valence state of Pton the surface layer increases under the action of surface oxygen.It exhibits superior specific activity(5.65 m A cm^-2)and mass activity(1087.00m A mg^-1)which are much better than those of commercial Pt/C.In addition,the CO oxidation peak potential of the material is about 40 m V lower than that of commercial Pt/C,which shows superior CO tolerance in weakening CO adsorption and promoting rapid oxidation and desorption of CO at lower potential.The morphology,surface microstructure,and electrocatalytic performance of Pt/Pd nanomaterials obtained by several different preparation methods were discussed.Combined with experimental analysis and theoretical calculation,the structural evolution of catalysts during the different synthesis processes and influence mechanism on their properties are revealed.The effective strategies of catalyst synthesis and property modification based for alcohol oxidation reaction are proposed,which can provide useful reference for the structural design and control of catalysts,and promote the research and development of direct alcohols fuel cells.