Study On Properties Of FePd Nanoparticles Prepared By Solvothermal Method

FePd nanoparticles have attracted considerable interest because of their high coercivity,large uniaxial magnetocrystalline anisotropy and good chemical stability.In this paper,the effects of reducing agent(1,2-hexadecanediol and PEG-400),the ratio of Fe(acac)3/Pd(acac)2 on the microstructure,morphologies,phase fraction,magnetic and catalytic properties of FePd nanoparticles prepared by solvothermal method were studied.The as-synthesized samples are superparamagnetic and contain chemically disordered fcc-FePd and Fe3O4 phases.The fcc-FePd nanoparticles are spherical-like shape,and the Fe3O4 particles are petal-like or flake-like shape.After annealing at 550℃ for 1h,the fcc-FePd phase transforms to fct-FePd phase and the Fe3O4 phase transforms to a-Fe phase.Futhermore,the samples changed from superparamagnetic to ferromagnetic.The electrochemical active surface area(EASA)and catalytic activity for ethanol oxidation increased after annealing.When the nanoparticles were prepared by using 1,2-hexadecanediol as the reducing agent,the average size of fcc-FePd is 2.6～4.1 nm.The effect of 1,2-hexadecanediol concentration on the properties of FePd nanoparticles was studied.The results show that with the increase of 1,2-hexadecanediol concentration,the particle size and phase fraction of fcc-FePd in as-synthesized samples and fct-FePd in annealed samples increased at beginning then decrease,the lattice parameter a and c/a decreased at beginning then increased.The samples with 1,2-hexadecanediol:Fe(acac)3=5:1 has the biggest amount of fcc-FePd(as-synthesized,77.25%)and fct-FePd(annealed,81.98%),largest particle size(as-synthesized:4.1nm,annealed:20.4nm)and smallest a[3.9147(6)A]and c/a(0.9573).The EASA of as-synthesized and annealed samples both increase when increasing 1,2-hexadecanediol concentration increase,and reach maximum when 1,2-hexadecanediol:Fe(acac)3=5:1(as-synthesized:35.6 cm2/mg,annealed:37.1 cm2/mg),then decrease.The peak current density(as-synthesized:51.9 mA/mg,annealed:52.4 mA/mg)and catalytic activity for ethanol oxidation has the same tendency.When the nanoparticles were prepared by using PEG-400 as the reducing agent,the average size of fcc-FePd is 2.9～4.3nm.The effect of PEG-400 concentration on the properties of FePd nanoparticles was studied.The results show that with the increase of PEG-400 concentration,the particle size and phase fraction of fcc-FePd in as-synthesized samples and fct-FePd in annealed samples increased at beginning then decrease,the lattice parameter a and c/a decreased at beginning then increased.The samples with PEG-400:Fe(acac)3=5:1 has the biggest amount of fcc-FePd(as-synthesized,66.50%)and fct-FePd(annealed,84.13%),largest particle size of FePd(fcc:4.3nm,fct:22.1 nm)and smallest lattice parameter a of fcc-FePd[3.9358(9)A)]and c/a of fct-FePd(0.9569).The EASA of as-synthesized and annealed samples both increase when increasing PEG-400 concentration increase,and reach maximum when PEG-400:Fe(acac)3=5:1(as-synthesized:19.2 cm2/mg,annealed:27.5 cm2/mg),then decrease.The peak current density(as-synthesized:7.7 mA/mg,annealed:36.8 mA/mg)and catalytic activity for ethanol oxidation has the same tendency.The nanoparticles were prepared by using PEG-400 as the reducing agent,Fe(acac)3 and Pd(acac)2 with different ratio as the precursors.The effect of Fe(acac)3/Pd(acac)2 ratio on the properties of FePd nanoparticles was studied.The results show that the average size of fcc-FePd is 2.9～6.4 nm.With the increase of Fe(acac)3/Pd(acac)2 ratio,the particle size and phase fraction of fcc-FePd in as-synthesized samples decreased,lattice parameter increased.The particle size,phase fraction and c/a of fct-FePd in annealed samples increased with increasing Fe(acac)3/Pd(acac)2 ratio.The as-synthesized sample with Fe(acac)3/Pd(acac)2=0.6:1 has the biggest amount of fcc-FePd(86.55%),largest particle size of FePd(6.4nm)and smallest lattice parameter[a =3.9065(4)A].The annealed sample with Fe(acac)3/Pd(acac)2=1:1 has the biggest amount of fct-FePd(76.44%),largest particle size of FePd(16.8nm)and biggest c/a(0.9632).The coercivity of annealed sample with Fe(acac)3/Pd(acac)2=1:1(1.8 kOe)is larger than that annealed sample with Fe(acac)3/Pd(acac)2=0.8:1(1.2kOe)and 0.6:1(0.35 kOe).The EASA of as-synthesized samples decreased with increasing Fe(acac)3/Pd(acac)2 ratio.The samples with Fe(acac)3/Pd(acac)2=0.6:1 has the biggest EASA(as-synthesized:47.9 cm2/mg,annealed:51.6 cm2/mg),highest peak current density(as-synthesized:59.4 mA/mg,annealed:66.1 mA/mg)and catalytic activity for ethanol oxidation.The nanoparticles were prepared by using PEG-400 as the reducing agent,The effect of synthesis temperature on the properties of FePd nanoparticles was studied.The results show that the average size of fcc-FePd is 2.7～4.5 nm.With the increase of synthesis temperature,the particle size of fcc-FePd in as-synthesized samples increased,lattice parameter increased at beginning then decreased,phase fraction increased obviously when synthesis temperature up to 200℃.With the increase of synthesis temperature,the particle size and c/a of fct-FePd in as-synthesized samples increased,lattice parameter decreased.The samples synthesized at 200℃ has the biggest amount of fcc-FePd(as-synthesized,79.38%)and fct-FePd(annealed,83.27%),largest particle size of FePd(fcc:4.5nm,fct:19.3nm)and smallest lattice parameter a of fcc-FePd[3.9340(2)A]and c/a of fct-FePd(0.9489).The coercivity of annealed samples increased with the synthesis temperature,the annealed samples synthesized at 200℃ has the biggest intrinsic coercivity(2.2kOe).The samples synthesized at 200℃ has the biggest EASA(as-synthesized:20.1 cm2/mg,annealed:34.6 cm2/mg),highest peak current density(as-synthesized:14.8 mA/mg,annealed:37.4 mA/mg)and catalytic activity for ethanol oxidation.