The Study Of Electrocatalyst For Oxygen Reduction From Egg-white

Fuel cells have become the most promising novel energy source because of theproperties of high energy-conversion efficiency, abundant sources of fuel andenvironmental benefits, compared with other types of energy sources. It is well-knownthat the electrocatalysts are a key component of fuel cells. At present, Pt-basedelectrocatalysts are the best and most frequently used catalysts for the oxygen-reductionreaction （ORR）. However, Pt-based materials have limited fuel-cell commercializationdue to their high cost, scarcity and poisoning phenomenon. Therefore, preparing thecatalysts with low cost, better electrocatalytic activity, good stability and bettertolerance to methanol is one of the key to solve those problems.This paper was the first time to adopt native egg-white protein （Ew） as N source,and the ORR electrocatalyst was prepared by liquid impregnation combined with hightemperature treatment process. The influences of the choice of metal precursors,precursor compositions, metal loadings, heat-treatment temperatures and heat-treatmenttime on the electrocatalytic activity were studied extensively. Linear sweep voltammetrywas used to investigate the electrocatalytic activity and stability, and methanol-tolerancewas evaluated by cyclic voltammetry. Meanwhile, the structure of the prepared catalystwas characterized by XRD and TG/DTA.The results indicated that the nature of the metallic center in the precursor andmetal content played vital role in activity improvement. The catalyst using FeCl₃·6H₂Oas metal precursor shows higher catalytic activity for the ORR in0.5mol/L H₂SO₄saturated with oxygen, and the optimal metal content for Fe was satisfied with theatomic ratio （6:1） of N to Fe. Metallic Fe is not active site, but it can better facilitate theformation and maintain of active sites, and the stability and methanol-tolerance ofFeEw/C is better than Ew/C, which agreed with the result of XRD. The nature of ORRcatalytic active sites need to be further studied for FeEw/C.The experimental results demonstrated that catalytic activity also was closelyrelated to heat-treatment temperature and time. The FeEw/C catalyst achieved theoptimum activity when the heat-treatment temperature and time were800℃and2h,respectively. The choice of temperature was basically in accroding with the TG/DTA.The onset reduction potential and peak potential of the catalyst prepared by the bestcondition are0.52V（vs.SCE） and0.44V （vs.SCE）, respectively.