微生物燃料电池Fe-N掺杂炭黑阴极催化剂性能研究

Fe-N Modified Carbon Black as a High-performance and Cost-effective Cathode Catalyst in Microbial Fuel Cells

炭黑是一种廉价且具有高导电性的氧还原催化剂,可应用于微生物燃料电池(MFCs)的阴极。然而,纯炭黑的催化性能较差,不能满足实际应用需求。为了提高炭黑的催化性能,以氯化铁(FeCl_3)和三聚氰胺作为Fe源和N源按一定比例与炭黑混合共炭化,对炭黑进行改性处理。结果表明,当Fe-N与炭黑的质量比例为2.6∶1时,MFCs的输出功率密度达到最高值,为1395 mW/m^2,比Pt/C催化剂(876 m W/m^2)提高了59%。SEM观察到炭黑基体上形成了椭圆形或柱状晶体,XRD和XPS测试结果显示是在共炭化过程中生成的Fe3C晶体,引入了吡啶氮和石墨氮,在催化剂表面形成更多的活性位点,这是复合催化剂性能提升的关键因素。随着Fe-N比例的提高,复合催化剂的导电性和比表面积逐渐下降,从另一方面又限制了其性能的提升。综上所述,氯化铁、三聚氰胺和炭黑共炭化制备的复合催化剂是一种具有良好性价比的MFCs阴极催化剂,可在规模化应用中发挥更大作用。

Carbon black is a high conductive and cheap catalyst for oxygen reduction,which can be used as cathode catalyst of microbial fuel cells.However,pure carbon black has low catalytic activity which does not meet the requirement in practical field.In order to improve the catalytic performance of carbon black,ferric chloride（FeCl3） and melamine,as sources of Fe and N respectively,were mixed with carbon black at a certain ratio and co-carbonized.Results show that the output power density reaches the highest value（1395 mW/m2） with the mass ratio of 2.6∶1（FeCl3-melamine/carbon black）,which is 59% higher than that of the widely used Pt/C catalyst（876 mW/m2）.SEM images show that some elliptic or columnar crystals are formed on the surface of carbon black,which is testified to be Fe3C crystal by XRD and XPS.Meanwhile,pyridinic and quaternary nitrogen generated by carbonization provides more active sites on the catalyst surface,thus improving the catalytic performance of composite catalyst.With the increasing ratio of Fe-N,the conductivity and the surface area of composite catalyst decrease gradually,which limits the catalytic performance.All those data demonstrated that the catalyst generated by FeCl3,melamine and carbon black is an exceptional cost-effective cathode catalyst which can be used in scale-up MFCs.