Fabrication And Electrocatalytic Properties Of Nanoporous Fe-Pt Alloys

Nanoporous metals with three-dimensional bicontinuous ligament/channel structure have promising application potential in catalysts,heat exchangers,actuators,energy storage and biosensors due to their fascinating physicochemical properties.Nanoporous Pt metals and Pt alloys have attracted considerable attention as anodic catalysts of fuel cells in terms of their high catalytic activity for methanol oxidation reaction?MOR?.Various kinds of nanoporous metals have been fabricated from solid solution alloys by dealloying which is one of the effective approaches to produce nanoporous metals.In comparison with solid solution alloys,the amorphous alloys have been highly expected to be an ideal candidate,because they have more than thousands of multicomponent alloy systems with changeable component elements and relatively wide composition ranges,and they present a more chemically homogeneous nature which is absent of crystalline defects and large scaled phase segregations.Some nanoporous single metals,such as Cu and Pd have been synthesized by dealloying the amorphous precursors.However,there are few work on the fabrication of nanoporous bimetallic alloys by dealloying the amorphous alloys.It has been reported that the nanoporous Pt-Fe,Pt-Co and Pt-Ni alloys have been fabricated from the solid solution alloys,and show enhanced electrocatalytic activity for MOR than the nanoporous Pt alloys.In this work,we selected Fe-Pt-B amorphous alloys as dealloying precursors to study the effects of precursors to their compositions,morphologies and electrocatalytic activities for MOR of the prepared nanoporous alloys by X-ray diffraction?XRD?,transmission electron microscopy?TEM?,scanning electron microscope?SEM?equipped with an Oxford X-ray energy-dispersive spectroscope?EDS?and a standard three-electrode system?Interface 1000?.We tested their magnetic properties by vibrating sample magnetometer?VSM?.The results are as follows:1.Nanoporous Fe-Pt alloys composed of a single face-centered-cubic FePt phase have been fabricated by electrochemically dealloying Fe_90-xPt₁₀B_x?x = 25,27.5,30?and Fe_75-yPt_yB₂₅?y = 10,12.5,15?amorphous alloys in 0.1 mol/L H2SO4 solution.The nanoporous Fe-Pt alloys possess fine bicontinuous ligament/channel structures with average pore sizes of about 3¹5 nm.2.The nanoporous Fe-Pt alloys fabricated from Fe_90-xPt₁₀B_x?x = 25,27.5,30?amorphous alloys possess ligament/channel structures with average pore sizes of about 4⁶ nm,and the atomic ratio of Pt/Fe are 57.13/42.87⁶4.68/35.32.The increase in component B content has few influence in the average pore sizes of the nanoporous Fe-Pt alloys,while it improves the atomic ratio of Pt/Fe of them.3.The nanoporous Fe-Pt alloys fabricated from Fe_75-yPt_yB₂₅?y = 10,12.5,15?amorphous alloys possess ligament/channel structures with average pore sizes of about 3¹5 nm,and the atomic ratio of Pt/Fe are 57.13/42.87⁶5.02/34.98.The increase in component Pt content improves the average pore sizes and atomic ratio of Pt/Fe of the nanoporous Fe-Pt alloys.4.The nanoporous Fe-Pt alloys exhibit superior electrocatalytic activity for MOR in the acid media to the commercial Johnson Matthey Pt/C catalyst.The increase in component B content improves electrocatalytic activity for MOR of the nanoporous Fe-Pt alloys.While the increase in component Pt content decreases the electrocatalytic activity for MOR of it.This is related to the atomic ratio of Pt/Fe and average pore sizes of the nanoporous Fe-Pt alloys.5.The saturation magnetization of Fe₆₀Pt₁₀B₃₀ amorphous alloy decreases from 121.49 to 19.09 emu/g,while the coercivity increases from 0.46 to 8.71 Oe after dealloying.This is due to the changes of structures and compositions with dealloying.