Controllable Synthesis,Structural Characterization And Electrochemical Properties Of Palladium-Based Nanocrystals

As the global population increases and climate changes,people are pay more attention to energy.Fuel cells are a promising energy conversion system that is far more efficient than conventional combustion,and the final product is usually just H₂O and CO₂.It is because of these advantages such as green and clean fuel cell that it has gradually become the key research objects in the direction of new energy.Platinum（Pt）and platinum-based nanomaterials have always been the most effective catalysts for ORR,but there are some defects when widely used in fuel cells.For example,high price and cost,easy poisoning and other defects in the test process.In this context,Pd and Pd-based nanomaterials were found to be potential substitutes for platinum in electrochemical energy conversion processes.Because Pd and Pt belong to the same family in the periodic table of elements,and Pd,also as precious metal,has the same face-centered cubic structure,it has become an excellent candidate to replace Pt and has aroused increasing interest of researchers.In this paper,we have prepared uniform truncated angle tetrahedral Palladium（T-Pd-Ths）with the morphology and size of about 13.4 nanometers by solvothermal method.Pd（acac）₂ was used as the metal precursor and N,N-dimethylformamide（DMF）and glycerol were used as the solvent of the reaction,polyvinylpyrrolidone（PVP-8000）was used as the surfactant,including formaldehyde,Mo（CO）₆ and other reagents.In alkaline medium,T-Pd-Ths/C showed high oxygen reduction（ORR）activity and excellent resistance to carbon monoxide（CO）toxicity.It is verified that the ORR process is a typical 4-electron process by RRDE experiments.Furthermore,T-Pd-Ths/C has demonstrated extremely high durability after 50,000 cycles,with a mass activity loss of only 7.69%after 50,000 cycles of ADT durability.Notably,in actual direct methanol fuel cell（DMFC）device,the T-Pd-Ths/C delivers superior open-circuit voltage（OCV）and peak power density（PPD）to commercial Pt/C from 25 to 80℃.Then,using Pd（acac）₂ as metal precursor,we studied the effects of changing reagent and reaction conditions on the catalyst morphology by using control variable method.In the presence of Mo（CO）₆,a large number of nano-catalysts with flake structure were synthesized and characterized by ICP-OES.The crystal was found to be pure palladium.The XRD results show that the crystal has typical face-centered cubic structure（fcc）.We found that the products had better oxygen reduction（ORR）performance.Under alkaline conditions,the mass activity of ORR was 1.55 A mg^-1.After 10,000 cycles of durability testing,mass activity decreased by 14.2%,showing a good stability.In 0.1 M HCl O₄+0.5 M HCOOH test environment,it shows good formic acid performance.