Plasma Synthesis Of Transition Metal-based Oxygen Defect-rich Heterostructure Catalysts For Rechargeable Zinc-air Batteries

With the continuous development and updating of the energy industry,With the continuous development and updating of the energy industry,new energy conversion systems such as zinc-air batteries are being formed and improved.For rechargeable zinc-air batteries（ZAB）,the oxygen evolution reaction（OER）that occurs during charging and the oxygen reduction reaction（ORR）that occurs during discharge of the air cathode are key factors that affect the performance of ZAB.However,the current commercial catalysts still have the disadvantages of high cost and poor stability,which greatly affects the market application of ZAB.Therefore,it is crucial to develop efficient,stable,and low-cost air cathode catalysts for the development of ZAB.RF plasma enhanced chemical vapor deposition technology（RF-PECVD）is a new type of material modification technology,which can achieve surface engineering such as material surface modification and heteroatom doping under the premise of low energy consumption and no pollution.In this paper,a nickel-cobalt-based heterostructure bifunctional catalyst loaded on carbon nanotubes was prepared by RF plasma-enhanced chemical vapor deposition based on the high OER activity of transition metal Ni,Co and Fe-based compounds and the high ORR activity of carbon nanotubes.The main research contents of this paper are as follows:（1）NiCoO/Ni Co N heterostructured nanowire composite catalysts（P-NCO/NCN-CF@CC）with carbon cloth-loaded carbon fibers and oxygen defect-rich were successfully synthesized by RF-PECVD technique,which contains advanced properties such as carbon integration,cation doping,defect/vacancy introduction and heterostructure,and exhibits a novel core-shell structure:the exterior is composed of Ni Co O_x on the outside and Ni Co O_x and Ni Co N_x together on the inside.It was found by optical emission spectra（OES）that its formation is mainly due to the high reactivity of NH,Hαand Hβreactive species formed during the plasma discharge.In electrochemical tests,P-NCO/NCN-CF@CC exhibited ORR activity comparable to that of Pt/C and higher OER activity than Ru O₂.The excellent bifunctional properties were found to arise from the large number of oxygen defects generated on the material surface after plasma treatment by DFT calculations.When used in all-solid-state zinc-air batteries（SS-ZAB）,its maximum power density was able to reach 109.8m W cm^-2 and remained stable over 300 charge/discharge cycles.（2）Nitrogen-doped carbon microtubules（CMTs@CC）were synthesized by high-temperature calcination on carbon cloth as a substrate for hydrothermal synthesis of Ni Co Fe hydroxide nanowires（NCFLDH@CMTs@CC）,and finally,a heterostructured material loaded on carbon cloth with NCFO@NCFN/NCF was obtained by two RF-PECVD technique（P-NCFO@NCFN/NCF@CMTs@CC）.It possesses excellent OER/ORR bifunctional catalytic activity.The physical phase analysis by XRD and XPS reveals that NCFO@NCFN/NCF is composed of Ni Co Fe O_x,Ni Co Fe N_x and Ni Co Fe alloy together,and the key to its synthesis is the reduction of Ni Co Fe metal nanowires on the material surface by Ar/NH₃ plasma at high temperature,which enhances the electron conduction and charge transfer ability of the material,while the subsequent O₂ plasma treatment increased the active sites on the surface of the material,forming a large number of oxygen vacancies and thus enhancing its catalytic performance.In conclusion,this thesis aims to synthesize high-performance ORR/OER bifunctional catalysts using a novel plasma-enhanced chemical vapor deposition method to improve the ORR/OER bifunctional catalytic activity of the materials by constructing nanomaterials with heterogeneous structures,high specific surfaces and fabricating oxygen defects,thus applying them to rechargeable zinc-air batteries,which provides a new idea for the development of efficient cathode catalysts for zinc-air batteries.