FeNi@nanoporous Carbon Composite Construction And The Electrocatalytic Synthesis Of Urea

With the increase of human activities and the overuse of fossil fuels,the excessive emission of CO₂ into the atmosphere makes the problem of energy,environment and climate change increasingly prominent.Converting CO₂ into valuable industrial chemicals not only reduces the concentration of CO₂,but also offers a promising strategy for the sustainable development of global carbon balance.Fertilizer intensive agricultural and industrial emissions lead to nitrate pollutants,which seriously threats to human health and environmental security.The electrosynthesis of urea by C-N coupling reaction by electrocatalysis between carbon dioxide and nitrate provides a promising way to reduce the environmental impact of industrial production and increase the value of wastes in various industrial processes.Compared with single metal catalysts,alloy catalysts can not only enhance the synergistic effect between active metal sites,but also improve the catalytic performance and selectivity of metal.Hence,this paper mainly carried out the following research work:（1）Firstly,by the wet impregnation method,using porous nanocarbon as the carrier,we in situ synthesized FeNi-nitroprusside loaded on the nanoporous carbon composites（FeNi-NP@C,NP stands for nitroprusside）.Through high temperature pyrolysis,the FeNi-nitroprusside was transformed into FeNi alloy and nanoporous carbon composites loaded with FeNi alloy（FeNi@C）have been prepared.In addition,FeNi@2C-900,FeNi@2C-1000 and FeNi@2C-1100 composite materials were prepared by changing the calcination temperature during the synthesis process（900,1000 and 1100 indicate that the calcination temperature is 900℃,1000℃and 1100℃respectively）.By changing the amount of nanoporous carbon incorporated,the composite materials of FeNi@1C-1000,FeNi@2C-1000,FeNi@3C-1000,FeNi@4C-1000 and FeNi@5C-1000 were prepared（1,2,3,4 and 5 indicated that the mass of added nanoporous carbon was 1 g,2 g,3 g,4 g and 5 g,respectively）.The experimental results show that the introduction of nanoporous carbon can not only control the size of FeNi alloy within the nanometer range,but also significantly improve the stability of the catalytic process of the material.Fe and Ni bimetallic sites are used for the adsorption and activation sites of NO₃^-and CO₂ respectively,which can simultaneously achieve the electrochemical co-reduction of NO₃^-and CO₂,and cooperatively promote the activity of electrocatalytic C-N conjugations into urea.The optimized urea yield and Faradaic efficiency over FeNi@2C-1000 can reach 9.2mmol h^-1 g^-1 and 11.2%at-1.2 V vs.RHE（reversible hydrogen electrode）.This work successfully achieved the synthesis of urea at room temperature and provided new insights for the fixation and conversion of NO₃^-and CO₂.（2）On the basis of the synthesis of FeNi@C by wet impregnation and high temperature pyrolysis method,the FeNi@C-M was further expanded to achieve batch synthesis of hectogram scale.The produced FeNi@C-M catalyst can improve the C-N coupling with NO₃^-and CO₂ as feedstacks,reaching 13.2 mmol h^-1 g^-1 of urea yield at-1.3 V vs.RHE.This work has practical significance for designing cheap,efficient and stable electrocatalysts.