Synthesis And Electrocatalytic Performance Of High Entropy Nanoalloys And Their Phosphorus/sulfide

High-entropy nanoalloys are a new class of metallic nanomaterials,which are currently defined as the incorporation of five or more elements（The concentration of each element is 5 and 35 at%）into a single-phase solid solution in near molar ratios formed alloy.Due to their outstanding properties in the field of electrocatalysis,there are increasing studies on the synthesis of different high-entropy nanoalloys and their derivatives.High-entropy nano-alloys have a huge specific surface area and can show lots of active sites,and they can enhance the electrocatalytic property through the synergistic effect between elements,which has a good advantage in electrochemical reactions.The composition,size,and structural characteristics of high-entropy nano-alloys will affect their performance and stability,so the controllable preparation of high-entropy nano-alloys is very important.In this thesis,the liquid metal potassium-sodium alloy is used as a powerful reductant to rapidly reduce five immiscible metal salts by shear-assisted method at room temperature,thus combining the five elements to form a high-entropy nanoalloy.On this basis,the synthesized high-entropy nano-alloys were post-treated under different conditions to obtain different kinds of high-entropy nano-metal derivatives.The specific research contents are as follows:（1）A novel method for the synthesis of platinum-based high-entropy alloy nanoparticles（HEA NPs）using a shear-assisted liquid metal reduction strategy at room temperature was developed.The high-entropy nano alloy particles synthesized by the method are uniformly dispersed on the sibunit.By selecting four elements Fe,Co,Ni,Pt as fixed elements,the fifth element as a variable element（transition metal element）to further adjust the surface strain and electronic properties.We have successfully synthesized a very small size（1～3nm）carbon-supported HEA Co-Fe-Ni-Pt-Ta-vxc72NPs,when it is used for electrocatalytic hydrogen evolution reaction and oxygen evolution reaction,which can obtain an outstanding electrochemistry performance and stability.At a current density of 10 m A cm^-2,the overpotential corresponding to the hydrogen evolution reaction（HER）of Co-Fe-Ni-Pt-Ta-vxc72 alloy in 0.5 M H₂SO₄electrolyte is only 10.6 m V;In 1.0 M KOH electrolyte,the overpotential of oxygen evolution reaction（OER）is 290 m V.The electrocatalytic performance of Co-Fe-Ni-Pt-Ta-vxc72 alloy is superior to that of standard catalysts（Pt/C and Ir O₂）for both HER and OER.（2）A method for the synthesis of high-entropy nanoalloy phosphides was developed.First,the carbon-supported quinary high-entropy nanoalloys were synthesized by shear-assisted reduction method,and then a series of high-entropy metal phosphides（HEMPs）were obtained by phosphating treatment with sodium dihydrogen phosphate as the phosphorus source.Among them,the synthesized Co-Fe-Ni-Mo-Ca-P composite has the best electrocatalytic performance and stability when it is subjected to electrocatalytic oxygen evolution reaction.The Co-Fe-Ni-Mo-Ca-P composite can reach a current density of 10 m A cm^-2at only 260 m V overpotential;in addition,its stability can reach 30 h under the chronoamperometry,indicating that it has a relatively good stability.（3）A method for the synthesis of high-entropy nanoalloy sulfides was developed.First,carbon-supported quinary high-entropy nanoalloys:Co-Fe-Ni-Mn-Cr vxc72 were synthesized,and then sulfur powder was used as the sulfur source for sulfide treatment to obtain high-entropy metal sulfides（HEMS）.The optimal electrocatalytic performance after sulfidation was explored by controlling the mass ratio of HEA and sulfur powder during mixed grinding（1:1,1:5,1:10,1:15,1:20）as variables.It was found that at the sintering temperature of 300℃,the best electrocatalytic oxygen evolution reaction performance was obtained when the mixed grinding mass ratio of HEA and sulfur powder was 1:10.It can achieve a current density of 10 m A cm^-2with only 240 m V overpotential in 1.0 M KOH electrolyte,outperforming most OER catalysts.