The Optimized Synthesis Of Different Forms Of PdM Alloy And The Study Of Its Electrocatalytic Performance For Formic Acid

Fuel cell is a device that directly converts chemical energy into electrical energy through an electrode reaction.It has been widely conceemed by researchers with remarkable characteristics of green,high efficiency,and environmental protection,which does not involve any combustion diiring the reaction.Among them,direct formic acid fuel cell(DFAFC)stands out because of its non-toxic,safe and non?flammable,low permeability to Nafion membrane.At present,preeious metal Pd has been recognized as one of the recognized DFAFC catalysts.However,the widely use of Pd-based catalysts still suffer from the high cost,unsatisfactory activity and stability.Therefore,it is significantly to regulate the structure and composition of Pd-based catalysts and further improve the Pd utilization.As demonstrated previously,several approaches could be applied for the improvement of the electro-activity and the utilization of noble metal Pd summarized as following:1.modification with the second/third cost-effective metal(Fe,Co,Ag),by which the crystal and surface electronic structure can be tuned,and combined with the synergistic effect of the formed alloys for enhancement of the electrocatalytic activity.2.loading the catalyst on appropriate support with good conductivity and high specific surface area.Those matrix usually include activated carbon(AC),graphene(G),and carbon nanotube(CNT),which can greatly increase the stability and the catalytic activity of the catalysts.3.control of the morphology over kinetic process design,by which the specific surface area will be enlarged with increased surface active sites,therefore effectively boosting the electrocatalytic efficiency of the catalyst.Above all,three different kinds of approaches were designed to improve the electrocatalytic performance of the Pd-based catalysts toward the DFAFCs.1.Synthesis of the carbon-supported PdM(M=Co,Fe,Ni)alloyed nanodendrites with homogeneous morphology through the direct thermal decomposition methods.The morphology,structure,and composition of the dendrites were fully characterized through a series of approaches like TEM,EDX,XRD and XPS.The electrochemieal test results showed due to the dendritie structural features and alloyed synergy,the as-synthesized PdCo nanodendrites/C catalyst could afford amass current density of 2467.7 A g-1,which is almost 3.53 and 10.4 times higher than those of lab-made Pd/C-control(698.3 A g-1)and commercial Pd/C catalyst(237.6 A g-1),respectively.Furthermore,the PdCo nanodendrites/C catalysts also exhibit superior stability relative to the Pd/C catalysts.2.High-yield preparation of PdFe alloy tetrahedron by one-pot hydrothermal method.The TEM and XRD indicates the unique tetrahedral structure,the large specific surface area and the unique electronic effects of the PdFe alloy.The electrochemical test result shows that the mass current and the area current of the PdFe alloy tetrahedron were 595.8 A g-1 and 33.4 A m-2,which is almost 4.8 and 2.4 times higher than the commercial Pd black,respectively.Furthermore,the PdFe alloy tetrahedron were exhibited strong electrocatalytic stability and good resistance to CO toxicity.3.Fast and efficient synthesis the multi-branched PdAg nanodandelion(PdAg MBDs)by the N5N'-Methylenebisacrylamide(MBAA)served as the structure-directing agent.From the XPS spectra,the metal Ag can effectively change the electronic state of the Pd,and therefore improve the catalytic performance of the Pd catalysts.From the electrochemical test,the electrochemically active surface area(ECSA)of the PdAg MBDs were calculated as 21.13 m2g-1,which are almost 3.3 times higher than the conmercial Pd black(6.42 m2 g-1).Meanwhile,the formic acid oxidation reaction(FAOR)peak currents were reached to 319.6 A g-1,which are 2.7 times higher than the commercial Pd black(118.0 A g-1).