Preparation And Bifunctional Electrocatalyst Performance Of Silver Nanowires/CoNi Composite

Energy conversion devices such as hydrogen production by electrolysis of water,fuel cells,and metal-air batteries have received widespread attention due to their high energy conversion efficiency and green pollution-free characteristics.The slow oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)restricts the further development of these energy conversion devices.In view of the low conductivity,poor catalytic activity,and high cost of traditional noble metal OER and ORR electrocatalysts,it is urgent to develop electrocatalysts with high efficiency,durability,low cost,high exposed active surface and excellent conductivity.In this paper,solvothermal method is used to synthesize high aspect ratio silver nanowires(AgNWs),and AgNWs and CoNi alloy are compounded to obtain AgNWs@CoNi composite materials.The AgNWs@PPy@CoNi aerogels were prepared by freeze-drying and solvothermal methods,and the ORR and OER electrocatalytic properties of the two composites AgNWs@CoNi and AgNWs@PPy@CoNi aerogels were analyzed.The main contents are as follows:(1)The solvothermal method was used to prepare AgNWs,and the influence of reaction temperature,control agent type,control agent content and pressure on the micro morphology of AgNWs was studied.The results show that when the reaction temperature is 120°C,the content of nanoparticles and nanorods in the product is the least.When the control agent is Fe Cl₃ and the concentration is 39?M,there are almost no particles and nanorods in the product.When the reaction pressure is 2 MPa,the proportion of AgNWs whose diameter is 30-40 nm is about 10%.When the filling ratio of the solution in the reactor is 50%,the obtained AgNWs have a high degree of uniformity,and the number of AgNWs with a diameter of 40-60 nm accounts for about64%,and the diameter of 30-40 nm is about 8%.The small diameter AgNWs have a larger surface energy,which is helpful for the loading of CoNi alloy particles and the formation of core-shell structure.(2)The AgNWs@CoNi composite material was prepared by solvothermal method,and the influence of the concentration of surfactant PVP and Co²⁺and Ni²⁺in solvent glycol on the micro morphology of the material was studied,and the electrocatalytic performance of the composite material was analyzed.When AgNWs surface is coated with PVP,AgNWs@CoNi core-shell structure composite material can be obtained.With the increase of the concentration of Co²⁺and Ni²⁺,the number of CoNi alloys on the surface of AgNWs increases,and the particle size gradually increases,and its electrocatalytic performance shows a tendency to increase first and then decrease.When the concentration of Co²⁺and Ni²⁺is 0.015 M,the half-wave potential in the ORR performance test is 0.67 V,and the Tafel slope is 35.8 m V dec^-1.After a 10-hour stability test,the current density retention rate is about 87.1%.In the OER test,the overpotential of AgNWs@CoNi composite at a current density of 10 m A cm^-2 is 270m V,and the charge transfer resistance is 0.35?.After a 20-hour stability test,the current density retention rate is about 86.5%,and it has a good OER.performance.(3)The three-dimensional AgNWs@PPy aerogels was prepared by freeze-drying,and the influence of the concentration of pyrrole monomer in the mixed solvent of deionized water/ethanol on its microscopic morphology was studied.The results show that the thickness of the AgNWs@PPy aerogels shell increases with the increase of pyrrole concentration.(4)Prepare AgNWs@PPy@CoNi aerogels by solvothermal method,and study the influence of the concentration of Co²⁺and Ni²⁺in solvent glycol on its microstructure and electrocatalytic performance.The results show that with the increase of Co²⁺and Ni²⁺concentrations,the number of CoNi alloys on the surface of AgNWs@PPy aerogels increases,and its electrocatalytic performance first increases and then decreases.When the concentration of Co²⁺and Ni²⁺is 0.0175 M,in the ORR test,the half-wave potential of AgNWs@PPy@CoNi aerogels is 590 m V,and the limiting current density is 3.7 m A cm^-2.In the OER test,AgNWs@PPy@CoNi aerogels has an overpotential of 346 m V at a current density of 10 m A cm^-2,a Tafel slope of 86.25 m V dec^-1,and a charge transfer resistance of 0.1?.After 10 h stability test,the current retention rate reached 89.2%,and it has relatively good ORR and OER performance.