Transition Metal Doped Carbon Compositions Materials For Lithium-Sulfur Battery And Oxygen Reduction Reaction

Transition metal-doped nano-carbon materials combine the advantages of nano-carbon and transition metals and have excellent catalytic activity.They are widely used in lithium-sulfur batteries and electrocatalytic oxygen reduction reactions.Among transition metal nano-carbon composite materials,iron-doped nano-carbon materials belong to the category of higher catalytic activity,but there are still many problems,such as insufficient conductivity of carbon materials,poor ion-conducting ability,and unstable structure.Based on this,we designed a new iron-doped nano-carbon material and studied its role in lithium-sulfur batteries and oxygen reduction reactions.The iron/nitrogen co-doped carbon nanotube materials(Fe-N-CNTs)were prepared in one step by chemical vapor deposition,and a catalytically shaped bamboo-like hollow structure and high specific surface area composite was obtained.X-ray diffraction(XRD),Scanning electron microscopy(SEM),and transmission electron microscopy(TEM)confirmed the existence of Fe3C and Fe3N crystals and their bamboo-like hollow structure,improved the conductivity of carbon nanotubes.Morever,the Tafel slope and the change in the onset potential demonstrate the catalytic performance of Fe-N-CNTs,indicating that it accelerates the conversion reaction rate between polysulfides during the charge and discharge cycle.Furthermore,Fe-N-CNTs as a catalyst is also a carrier of elemental sulfur in a lithium-sulfur battery,which exhibits a higher capacity when it is loaded with elemental sulfur;in particular,when the sulfur loading reaches 13.12 mg cm-2,After 50 cycles,its specific capacity is still maintained at 9.10 mAh cm-1(current density is 2.2 mA cm-2).In addition,the photodeposition method is used to anchor the atomic Pt in Fe/N co-doped nano-carbon material(Fe-N-C)as a catalyst for oxygen reduction reaction.The Fe-doped metal-organic framework is a precursor,and the pyrolyzed Fe/N co-doped nano-carbon material has the characteristics of high specific surface area and high porosity,which can not only form atomic Fe,but also benefit Pt anchored.Due to the increase of active sites,atomic Pt-anchored Fe/N co-doped catalyst showed excellent electrocatalytic performance.The Pt1.1FeNC catalyst in the 0.1 M HClO4 electrolyte had a half-wave potential of 0.85 V vs.RHE,however,under the same test conditions,the commercial Pt/C has a half-wave potential of 0.83 V vs.RHE,which is 20 mV lower than the Pt1.1 FeNC catalyst.In addition,the stability test showed that the half-wave potential of the Pt1.1 FeNC catalyst was reduced by only 20 mV after 10,000 cycles.