Preparation And Electrochemical Performance Of Carbon Materials Derived From Transition Metal Complexes

With the development of modern industry and the improvement of human living standard,the excessive exploitation of traditional fossil fuels had caused serious pollution and damage to the ecological environment of the earth.Research and development of green new energy had become an important strategy to avoid environmental pollution and achieve sustainable development.The transition metal nitrogen-doped carbon materials（M-N-C）had the characteristics of low cost and high intrinsic catalytic activity,and can replace precious metals and precious metal-based catalysts,showing good application prospects in fuel cells and zinc-air cells.In this paper,two kinds of non-noble metal electrocatalysts were prepared by using a metal coordination polymer of guanine and a defect-rich g-C₃N₄ as precursors,respectively,and their applications in fuel cells and zinc-air cells were investigated.The main research contents are as follows:（1）Preparation and application of carbon materials derived from guanine metal-organic frameworks.The Fe/N doped carbon catalyst（Fe/N-C-900）was prepared by pyrolyzing the metal coordination polymer which was synthesized by the coordination between guanine and iron nitrate.Fe/N-C-900 was formed by the accumulation of irregular carbon nanoparticles（the diameter was 80-600 nm）.The specific surface area and the pore volume were 385.5 m² g^-1 and 1.0 cm³ g^-1,respectively.The nitrogen and oxygen content of Fe/N-C-900 were 2.31 at.%and 4.45at.%,respectively.In the alkaline medium,Fe/N-C-900 possessed better ORR catalytic performance than that of commercial Pt/C,together with good stability and methanol resistance.The open circuit voltage and power density of the Fe/N-C-900based primary zinc air battery were 1.52 V and 141 mW cm^-2,respectively,and the specific capacity is up to 814 m Ah g_Zn^-1 at the current density of 5 m A cm^-2.（2）Preparation and application of Fe/Ni co-doped carbon materials derived from maleic hydrazide-based organic framework.Bifunctional Fe/Ni doped carbon catalysts were prepared by pyrolyzing the mixture of Fe（NO₃）₃,Ni（NO₃）₂and defect-rich g-C₃N₄ which was synthesized by polycondensation of maleic hydrazide and melamine at high temperature.The catalyst（Fe Ni/N-CNT-1000）exhibited excellent bifunctional catalytic activity of ORR and OER.In 0.1 M KOH electrolyte,the ORR/OER potential difference was 0.832 V,which was close to the Pt/Ir composite electrocatalyst.The Fe Ni/N-CNT-1000 based secondary zinc-air cell can provide an open circuit voltage of 1.54 V,a peak power density of 127 m W cm^-2 and a specific capacity of 838 m Ah g_Zn^-1.After 1000 h of cyclic charging and discharging,the energy efficiency decreased by only 4%.