| A fuel cell is a device that converts the chemical energy of fuel into electricity.Fuel cells have attracted much attention because of their environmental friendliness.Fuel cells,whose byproducts are mainly waste heat and water,are non-polluting energy technologies.Cathodic oxygen reduction(ORR)mainly uses precious metals as catalysts which make it expensive and can not be produce at larger quantities.To commercialize fuel cells,low-cost ORR catalysts need to be developed.N,S,and other hetero-atom doped carbon materials are cheap,comparable to commercial Pt/C catalysts,excellent in stability,and can potentially replace precious metals as fuel cell ORR catalysts.In this research,porous carbon(graphite)materials doped with N,S,and other atoms have been studied.The catalytic activity and stability of ORR in the basic medium have been investigated.Firstly,N,S,and Fe doped graphite carbon from lotus stem(NSFe-LG)were synthesized.The effects of pore size,graphitization degree,N content,Fe content,and S content on ORR activity and stability were studied.The results show that the ORR performance of NSFe-LG in an alkaline medium is better than that of commercial Pt / C.The following electrocatalysts were synthesized NSFe-LG,NFe-LG,SFe-LG,and NS-LC and used as electrocatalysts for ORR in KOH media.The results shows,N plays a crucial role in ORR activity.Both Fe and S promote doping of N species while S itself and residual trace Fe itself(after HCl leach)contribute slightly to ORR activity.It was observed that,NS-LC shows higher ORR activity than the NFe-LG but,slightly less active than the NSFe-LG,this result indicating that S may replace Fe to get catalyst that has no metal.The doping of hetero-atoms can change the charge center of the carbon matrix and produce significant catalytic activity of ORR.The high doping concentration of heteroatom,large specific surface area,and high electrical conductivity significantly improve the activity and stability of the synthesized materials,which has potential commercial applications.Secondly,egg as biomass contains lots of vitamins,minerals,and protein.Egg white,yolk,and eggshell membrane are considered promising precursors with abundant heteroatoms,especially N,O,and S.The samples(EWs)were synthesized using different heating temperature of 580 °C,650 °C,720 °C,and 800 °C were defined as EW-580,EW-650,EW-720,and EW-800,respectively.The carbonized EW at 650 oC(EW-650)possesses ultrahigh surface area of(1904 m2 g-1),a large average diameter of 9.8 nm,high content of doped heteroatom(N,O and S),fairly high graphitization degree and dense defect.It was observed that,the EW-650 has higher catalytic activity and stability than EW-720,and EW-800 and commercial Pt/C in an alkaline medium.The synthesis process of the EW-650 is simple,less energy required for the preparation process indicating good economic value affordable. |
