Synthesis And Properties Of Sulfur Doped Porous Carbon Materials For CO₂ Capture And Oxygen Reduction Reaction

Owing to the high specific surface area and abundant porosity,porous carbon materials hold great potential in the fields of sorption,energy storage and conversion.Heteroatoms modified porous carbon materials normally show much improved properties.Owing to its wide range of resources,cost-effective and abundant pore structure,sulfur doped porous carbon is becoming a hot topic in recent years and has been widely used in gas sorption,lithium-ion batteries and fuel cells.Two different kinds of sulfur-doped porous carbons were successfully synthesized in this paper,and the abilities in carbon dioxide capture and oxygen reduction?ORR?electrocatalysis was systematically discussed,respectively.In the second chapter,sulfur doped porous carbon?S-PC?was synthesized by using benzo[b]thiophenc-3-carboxaldehyde as sulfur source via a template free method,and was tested as CO₂ adsorbent.The morphology and structure of S-PCs were characterized which showed that the S-PC possess high specific surface area with large quantity of micropores.The specific surface area and pore volume could be altered to high values of 997 m²·g^-1 and 0.44 cm³·g^-1,respectively.Besides,the basic S-C functional group of S-PC can offer strong acid-base interaction with acidic carbon dioxide gas.Owing to these fine characters,S-PC showed high CO₂ capacity,high values of 5.13 and 3.22 mmol·g^-1 could be achieved at 273 and 298 K,respectively.In the third chapter,2,2?-diaminodiphenyl disulfide was used as both C,N and S sources to realize simultaneously and in-situ doping of N and S heteroatoms.While FeCl₃·6H₂O was introduced as oxidant and template to induce the polymerization of 2,2?-diaminodiphenyl disulfide for assembling into 3D scaffold.The involved Fe species could also catalyst the graphitization of carbon materials and facilitate the formation of graphitized-N,pyridine-N and thiophene-S species which could enhance the activity towards ORR during calcination.After carbonization,the samples?FeNS/PC?showed high specific surface area of 816 m²·g^-1 with large pore volume of0.60 m³·g^-1.The high specific surface area and well-developed porosity could facilitate the transfer of reactant,electrolyte and product.When tested in O₂-saturated0.1 M KOH solution,FeNS/PC-800 showed superior ORR activity with onset-and half-wave potential of 0.95 V and 0.85 V,respectively.FeNS/PC-800 experienced a high selective 4e^-path ORR process,i.e.O₂ was directly reduced into OH^-.Moreover,FeNS/PC-800 also showed high long-term stability and high methanol tolerance,making it a competent candidate for ORR catalyst.