Study On The Properties Of Polyaniline Derived N-doped Carbon Materials In Electrocatalytic Reduction Of Carbon Dioxide

The excessive release of CO₂ emissions has caused serious environmental problems,such as global warming,rising sea levels,ocean acidification.In September2020,at the 75th Session of the United Nations General Assembly,China proposed to achieve"carbon neutrality"by 2060.Therefore,it is imperative to develop a green economy and sustainable methods to reduce carbon dioxide.Carbon dioxide can be converted into value-added chemicals using electrochemical reduction methods.Although the research on electrochemical CO₂ reduction has made satisfactory progress,tremendous efforts are needed to accelerate its large-scale production and application.The key to advancing the field of carbon dioxide electroreduction is to develop highly selective and highly active catalysts.Nitrogen-doped carbon catalyst have been widely studied for their low cost,wide source of raw materials and simple synthesis process.Doped nitrogen is mainly pyridine nitrogen,pyrrole nitrogen and graphite nitrogen,prepared by direct pyrolysis of carbon-based precursors,ammonia corrosion,soft/hard template.In order to expand the application range of nitrogen-doped carbon materials,we explore new nitrogen-doped carbon materials catalysts.Therefore,nitrogen-doped carbon catalyst with high concentration of imine nitrogen sites（48.1%of all nitrogen）were prepared by pyrolysis of polyaniline precursor was synthesized on the surface of multi-walled carbon tubes by chemical oxidation,and they can reduce CO₂ to CO with high selectivity and stability.Faraday efficiency of CO is 93%and the maximum current density can reach13.8 m A·cm^-2.Moreover,during 6 hours electrolysis at-0.62 V vs.RHE,Faradic efficiency for CO was stable at 90%.The relationship between the content of imine nitrogen and the catalytic activity was analyzed by XPS and Controlled potential electrolysis.It was confirmed that the optimal catalyst has the highest imine nitrogen content,which indicated imine nitrogen as the active sites for catalysis.Oxides can be used as a catalyst support and active components in catalytic systems,because it has high mechanical strength,good thermal stability,oxidation and reducibility and other physical and chemical properties.Oxide/carbon-based catalyst（Zr O₂/NC,Ce O₂/NC）was prepared by pyrolysis of oxide/polyaniline composite.The characterization of Zr O₂/NC and Ce O₂/NC catalysts showed that the metal oxide/nitrogen doped carbon compound exhibited excellent CO₂ reduction reaction activity compared with the nitrogen doped carbon（NC）alone.The maximum Faraday efficiency of Zr O₂/NC reached 90%at-0.73 V（vs.RHE）with the current density of CO was 5.5 m A·cm^-2,which is higher than NC（41%）with the current density of CO of 3.1 m A·cm^-2.