Electrodeposition Synthesis Of Porous Zn Anode And Cobalt-Iron Oxide Catalyst For Zinc-Air Batteries

Zinc-air battery is an ideal energy conversion and storage system because of its low price,clean and environmental protection,high energy density,and high charge and discharge efficiency.During the charge and discharge process,the negative electrode corresponds to the oxidation and reduction of zinc,and the positive electrode corresponds to the oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）.Current researches on zinc-air batteries mainly focus on catalysts and electrolytes,while researches on zinc anodes are relatively rare.The porous zinc electrodes have large specific surface areas and expose more active sites.Although the high specific surface areas may cause more severe corrosion,their higher reaction efficiency and faster charge and discharge rates still make them highly expected.For positive electrode materials,although noble metal catalysts have good catalytic performance,the problems of insufficient stability and high cost are still outstanding.It is reported that transition metal catalysts（nickel,cobalt,etc.）can obtain better OER and ORR catalytic performance through nitriding,sulfurizing,phosphating,cation regulation,and structural design,which is the mainstream method of current catalyst design.Electrodeposition can be used to cover the surface of the material with a thin film with certain functions.In this paper,the method was used for the synthesis of zinc anode and oxygen catalyst for zinc-air secondary battery.Firstly,we synthesized a three-dimensional honeycomb porous zinc electrode for zinc-air batteries by one-step electrodeposition method.In this work,we can load porous zinc on conductive substrates such as zinc foil,copper foil and porous copper,and the pore structure of porous zinc can be controlled by changing the synthesis parameters.The pore structure of porous zinc can be adjusted by changing the synthesis parameters,and it can be supported on conductive substrates such as zinc foil,copper foil,and porous copper.The significance of supporting porous zinc on the surface of zinc foil is to modify the surface of the zinc foil and form a porous film on its surface,which increases the specific surface area of the zinc electrode,brings higher electrochemical reaction activity,and further improves the performance of the zinc foil.The porous zinc anode has a smaller impedance（1.8Ω）than pure Zn.And zinc-air battery tests show that porous zinc has higher specific capacity（812 m Ah g-1）,higher efficiency（67.9%）,smaller overpotential（0.63 V）,and better cycle performance.In addition,we also prepared a cobalt-iron oxide catalyst with high-efficiency oxygen evolution catalytic activity by two-step electrodeposition-calcination method.Firstly,cobalt hydroxide,iron hydroxide,and cobalt-iron double hydroxide were prepared by electrodeposition,and then tricobalt tetroxide,iron oxide,and cobalt-iron oxide were obtained by calcination.The prepared cobalt-iron oxide has a low impedance（0.3Ω）,an OER overpotential of 287 m V（vs.RHE）at the current density of 10 m A cm^-2,and its stability is also good.It has better OER catalysis than pure cobalt trioxide performance.The introduction of trivalent iron element forms cobalt iron oxide with tricobalt tetroxide,which transforms the local structure from flaky to spherical.Moreover,the interaction between iron and cobalt changes the electron cloud of tricobalt tetroxide.The synergistic effect between the two components enhances the activity of the material and thus improves the catalytic performance.