The Controllable Synthesis Of Single Iron Atom Catalysts And Its Application For Electrocatalytic Reduction From CO₂ To CO

The massive combustion of fossil fuel makes the concentration of CO2 in the atmosphere increase year by year,leading to the increasingly serious greenhouse effect and other environmental problems.Driven by clean electric energy,the electrocatalytic reduction of CO2(CO2ER)into CO can not only reduce the accumulation of CO2 in the atmosphere,but also provide fuels for energy field.However,the reported catalysts for CO2ER generally have the problems of low selectivity,low current density,and high cost in preparation for now,so it is urgent to develop a kind of cheap electrocatalyst with both high selectivity and high current density.In this work,the single iron atom catalysts with excellent CO2ER electrocatalytic performance were successfully synthesized by developing novel synthesis strategies to control the generation of atomically dispersed iron atoms and iron carbide(Fe3C)nanoparticles.First,the single iron atom based nanocarbon electrocatalyst(FeiNC/Si-1000)with high activity was synthesized by gas diffusion strategy in this work,which is nitrogen doped carbon nanoparticles with atomically dispersed Fe atoms.The Fe1NC/S1-1000 catalyst achieved the current density of 6.4 mA cm-2 and CO Faraday efficiency of 96%at-0.5 V.The excellent catalytic activity of CO2ER is derived from the atomically dispersed Fe-N3 active site and the doping nitrogen in carbon skeleton.And the Fe-N3 active site can significantly reduce the energy barriers of generateing*COOH and*CO intermediate.Moreover,optimizing the size of carbon particles can improve the electrochemical active surface area,and increasing the carbonization temperature can increase the content of graphite nitrogen in catalyst and thus improve its CO2ER selectivity.Then,the Fe3C modified single iron atom based electrocatalyst was synthesized by solid phase strategy to control the generation of Fe3C in this work.The Fe3C|Fe1N4 catalyst achieved the CO Faraday efficiency up to 94.6%at-0.5 V,and the current density of 30 mA cm-2 at-1.05 V.The CO2ER activity of Fe3C|Fe1N4 originated from atomically dispersed Fe-N4 active sites,and the adjacent Fe3C nanoparticles improved the CO2 adsorption energy at the Fe-N4 active site,which further optimized the current density of CO2ER.In this work,the problems of low selectivity and low current density of CO2ER catalysts were solved by synthesizing new-type carbon-based single iron atom catalysts.At the same time,the catalysts were used as cathodes that assembled with Zn sheets to form novel Zn-CO2 batteries,which showed a high energy density,the recyclable rechargeability and the possibility of practical application.This work expands a broad application prospect of CO2ER in energy conversion and storage.