Design And Fabrication Of Porous Noble Metal Based High Entropy Alloys

High-entropy-alloys（HEAs）,as a class of emerging multi-component alloys,have inspired extensive research attention on physical properties owing to their high mixing entropy.However,the development and utilization of HEAs in catalysis,energy conversion and other fields have been greatly hindered due to the low specific surface area limited by traditional synthesis methods.Thus,it is important to design HEAs with high specific surface area.In this work,Cu Pd Ni Ag-based HEA microprism arrays and Cu Au Pt Pd-based quasi-HEA with nanoscale bicontinuous ligament/pore structure（np-Cu Au Pt Pd）were successfully synthesized by combining melt-spinning and dealloying processes.The effects of dealloying parameters on the pore structure were investigated,and the evolution mechanisms of pore structure were discussed.To prove utility,np-Cu Au Pt Pd was selected to prepare composite electrode materials for electrocatalytic nitrogen reduction reaction（NRR）performance testing.For the CuPdNiAg system,the Cu₃₅Pd₃₅Ni₂₅Ag₅ HEA ribbon with a dual-phase fcc structure was selected as the precursor.After chemical dealloying in 3 M HCl+1M HNO₃ for 7 h,the Pd O/Ag₂O/Ni O composite with a nanoscale bicontinuous ligament/pore structure（np-Pd O/Ag₂O/Ni O）was obtained.In addition,after chemical dealloying in 1 M HNO₃+0.5 M H₂SO₄ for 16 h,Cu element has been sulfurated during the long-term dealloying process,forming in a small amount of Cu₂S phase.Finally,by using electrochemical dealloying at 850 m V for 3 h in 1 M HNO₃+0.5 M H₂SO₄,Cu_30.0Pd_33.0Ni_30.4Ag_6.6 HEA microprism arrays were prepared successfuly.For the CuAuPtPd system,the Cu₉₇Au₁Pt₁Pd₁ alloy ribbons/microspheres were selected as the precursor.After chemical dealloying in 2 M HNO₃ for 24 h,the Cu Au Pt Pd-based quasi-HEA ribbons/microspheres（np-Cu Au Pt Pd-1/np-Cu Au Pt Pd-2）have been prepared.The as-obtained quasi-HEAs present a hierarchical porous structure with a high specific surface area and a multiphase approximatively componential solid solution characteristic with a broad single-group face-centered cubic XRD pattern,which is different from the traditional single-phase or two-phase solid solution HEAs.Moreover,in comparison with other noble nanomaterials,np-Cu Au Pt Pd-1 exhibits a higher NH₃ yeild rate of 17.5μg h^-1 mg^-1 at-0.2 V vs RHE owing to its unique hierarchical porous structure and synergistic effect.