Research On Preparation And Performance Of Functionalized MXene Supported Iron Phthalocyanine Oxygen Reduction Catalysts

Zinc-air batteries have received much attention because of their long lifetime,smooth discharge voltage,zero carbon emission and high theoretical energy density.The main reason limiting the efficiency of zinc-air batteries is the slow kinetic rate of oxygen reduction at the air electrode.Most current commercial catalysts are dominated by expensive and poorly durable noble metal catalysts.Therefore,the development of efficient,economical and stable oxygen reduction electrocatalysts has become a bottleneck problem for the application of zinc-air batteries.In this thesis,the preparation,physical properties,electrochemical properties and zinc-air battery performance of functionalized-MXene-based oxygen reduction catalysts were investigated mainly in terms of improving catalyst activity and stability.Firstly,Alk-MXene/FePc catalysts with three-dimensional petal-like structure were prepared by compounding iron phthalocyanine with alkaline MXene through alkaline treatment and ultrasonic liquid-phase compounding.The catalysts showed excellent oxygen reduction activity and stability in alkaline system with half-wave potential of0.924 V,limiting diffusion current density of 5.63 mA cm^-2.The peak power density of the zinc-air cell assembled with the Alk-MXene/FePc catalyst reached a peak power density of 191.5 mW cm^-2,which exceeded that of commercial Pt/C catalysts,and the peak power density at 10 mA cm^-2.A good long-term discharge stability was achieved at a current density of 10 mA cm^-2,exceeding 140 h,while the specific capacity reaches779.8 mAhg _Zn^-1.The effects of different alkalization time,alkalization concentration and iron phthalocyanine loading on the performance of Alk-MXene/FePc catalyst were investigated.When the alkalization time,alkalization concentration of Alk-MXene and the mass ratio of Alk-MXene to iron phthalocyanine was 8 h,0.5 mol L^-1,and 1:1,respectively,the best oxygen reduction performance of Alk-MXene/FePc catalyst was achieved.The NH₂-MXene/FePc catalyst with ultrathin two-dimensional nanosheet structure was prepared by compounding iron phthalocyanine with amino-functionalized MXene by APTES treatment and ultrasonic liquid-phase compounding.The catalyst showed excellent oxygen reduction activity and stability in alkaline system with half-wave potential of 0.921 V,Tafel slope of 54.26 mV dec^-1,limiting diffusion current density of5.56 mA cm^-2.The peak power density of the zinc-air cell assembled with NH₂-MXene/FePc catalyst reached 182.3 mW cm^-2,which exceeded that of commercial Pt/C catalysts.A good long-term discharge stability was achieved at a current density of 10mA cm^-2,exceeding 140 h,while the specific capacity reaches 774.7 mAhg _Zn^-1.The effects of different APTES treatment times and APTES treatment concentrations on the performance of NH₂-MXene/FePc catalysts were investigated When the APTES treatment time was 24 h and the APTES treatment concentration was 100μL,the best oxygen reduction performance of NH₂-MXene/FePc catalyst was achieved.