Preparation Of Porous Carbon Materials With Defect/Heteroatom Doping And Its Application In Li-CO₂ Battery

The rapid consumption of fossil fuels leads to the excessive emission of CO₂,which has caused serious damage to the original carbon cycle of the environment.The development of efficient catalysts to achieve high value-added conversion of CO₂and the development of high energy density metal-CO₂batteries are important means to solve the above problems,among which Li-CO₂batteries are favored by researchers due to their characteristics of cleanliness,no pollution and high theoretical energy density.However,the difficult decomposition of the discharge product Li₂CO₃leads to some problems such as poor rate performance,low capacity and poor cycle stability.Efficient cathode catalyst can improve the reaction kinetics of CO₂reduction during discharge and decomposition of Li₂CO₃during charge.Although noble metal based catalysts such as ruthenium show high catalytic activity,their high price and scarcity limit their large-scale application.Therefore,there is a need to develop low-cost and efficient non-precious metal catalysts.Based on the above background,this paper prepared two different low-cost and efficient porous carbon-based catalysts and applied them in the research of Li-CO₂batteries.The research contents are described as follows:1.Fe,N,S codoped porous carbon nanotube catalyst for Li-CO₂battery.Porous carbon nanotubes（Fe/N/S-h CNTs）doped with iron,nitrogen and sulfur were prepared by air oxidation method and heteroatom doping strategy and used as cathode catalysts for Li-CO₂batteries.Due to the abundant pore structure of Fe/N/S-h CNTs and the electron structure regulated by heteroatomic doping,Fe/N/S-h CNTs catalysts showed high catalytic activity of CO₂conversion in Li-CO₂cells.Li-CO₂cells based on Fe/N/S-h CNTs as cathode catalyst had a capacity of up to 20100 m A h g^-1at a current density of 500 mA g^-1,and could stably cycle for about 200 cycles at a cutoff capacity of 500 m A h g^-1.This study provides a new idea for the development of efficient and stable Li-CO₂cells and cathode catalysts in other fields.2.Defects rich porous carbon catalyst for Li-CO₂battery.Firstly,the precursor of MOF-5 was prepared by one-pot method,and a kind of porous carbon material（c-p-MOF-5）based on MOF-5 was prepared by introducing nano-Si O₂template.c-p-MOF-5 has abundant channels and defects,which help catalyze the conversion reaction of CO₂and storage of Li₂CO₃.At the current density of 0.5 A g^-1,the full discharge capacity of Li-CO₂battery based on the catalyst can reach 22,000 m A h g^-1,and the cutoff capacity of 500 m A h g-1 can be stable for 250 cycles.The results show that the Li-CO₂battery based on the catalyst has high capacity and cycle stability.