Fabrication And Catalytic Performance Towards H₂O₂ Reduction Of Hierarchically Nanoporous Structure From CoCrFeNiAl High-Entropy Alloys

As a kind of reactive oxygen species（ROS）,small molecule H₂O₂ is one of the important target analytes in environmental,biological,clinical and food application fields.Therefore,the accurate and rapid detection of H₂O₂ is very important.Among various H₂O₂ sensing techniques,non-enzymatic electrochemical sensing techniques have been widely studied because of their advantages of simple devices,rapid detection,low cost and high sensitivity.The transition metal materials with nanostructure are high potential catalyst material with excellent performance which can provide the large active surface area,good conductivity and catalytic activity.High-entropy alloys generally contain several transition metal elements with high catalytic activity.It is expected that the nanoporous high-entropy alloys exibit excellent catalytic performance due to the large specific surface area and multiple active elements.Electrochemical corrosion behavior of Co Cr Fe Ni Al series high-entropy alloy,the preparation of high-entropy nanoporous structure by dealloying and its H₂O₂ catalytic performance were investigated in this paper.The main contents are listed as followings:（1）The effect of Al content on the corrosion performance of Co Cr Fe Ni Si_0.1Al_x（x=0.5,1,2）in neutral and acidic environments was studied.The experimental results show that the corrosion resistance of Co Cr Fe Ni Si_0.1Al_x（x=0.5,1,2）high-entropy alloy in 3.5 wt%Na Cl and 0.5 M H₂SO₄ solutions decreases with the increase of Al content;（2）The Co Cr Fe Ni Al_x（x=0.9,1.0,1.2,1.5）high-entropy alloy ribbons obtained by the single-roll stripping method were used as the precursor,and the nanoporous structure NPCCF-x was prepared by dealloying.The effects of Al content,dealloying solution concentration and dealloying time on the porous structure were investigated.The experimental results show that under the same dealloying conditions,the more Al content,the easier it is for the sample to form a macroporous structure.After dealloying for 12 h in 1 M H₂SO₄,NPCCF-0.9 and NPCCF-1 samples only have small nanopores with diameters of～13.2 nm and～18.6 nm,respectively;NPCCF-1.2 has only single-level large pores with a diameter of～0.49μm and the depth of the pores is small;NPCCF-1.5 has a hierarchically nanoporous structure with an average pore diameter of～0.87μm for large pores and～13.2 nm for small pores.The pore size increases with the increase of dealloying concentration and dealloying time,accompanying with the decreasing of the ligament size.Combined with the microstructure characterization,the mechanism of dealloying has been preliminarily discussed;（3）The catalytic behavior of nanoporous materials obtained by dealloying towards H₂O₂reduction was studied.The NPCCF-1.5 electrode material has a higher sensitivity of 510.4μA m M^-1 cm^-2（the detection interval is 0.05-11.95 m M）compared with NPCCF-0.9,NPCCF-1and NPCCF-1.2.The high catalytic performance of NPCCF-1.5 electrode material is mainly due to its large electrochemically active area(1.64cm^-2),smaller charge transfer resistance R_ct（4.432Ω·cm²）,larger apparent heterogeneous electron transfer rate k(1.21 s^-1)and co-existing of multiple transition metal oxides.