Acta Phys. -Chim. Sin. ›› 2017, Vol. 33 ›› Issue (9): 1875-1883.doi: 10.3866/PKU.WHXB201705088

• ARTICLE • Previous Articles     Next Articles

Experimental Boosting of the Oxygen Reduction Activity of an Fe/N/C Catalyst by Sulfur Doping and Density Functional Theory Calculations

Chi CHEN1,Xue ZHANG2,Zhi-You ZHOU2,Xin-Sheng ZHANG2,*(),Shi-Gang SUN1,*()   

  1. 1 State Key Laboratory of Chemical Engineering, College of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, P. R. China
    2 State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
  • Received:2017-03-30 Published:2017-07-05
  • Contact: Xin-Sheng ZHANG,Shi-Gang SUN E-mail:xszhang@ecust.edu.cn;sgsun@xmu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21373175);the National Natural Science Foundation of China(21621091)

Abstract:

S doping in Fe/N/C non-precious metal catalysts is an effective approach to further improve their catalytic activity for the oxygen reduction reaction (ORR). However, the enhancement mechanism is not yet clear. Here, we synthesized an Fe/N/C catalyst using melamine-formaldehyde resin as the N and C precursors, CaCl2 as the template, and FeCl3 as the Fe precursor. The effects of S doping on the morphology, textural property, composition, and ORR catalytic activity were investigated by adding various amounts of KSCN as a precursor. Transmission electron microscopy (TEM) and N2 adsorption-desorption isotherm results revealed that S prevented the growth of Fe-containing nanoparticles, and facilitated the formation of a porous structure, which increased both the catalyst surface area and mass transfer rate. X-ray photoelectron spectroscopy (XPS) results indicated that a suitable amount of S precursor led to a high doping level of S and provided the highest ORR activity. However, too much S in the precursor decreased the doping levels of both Fe and S, due to the formation of FeS, which could be completely removed by acid leaching. Density functional theory (DFT) calculations showed that the addition of S in an Fe-N4 macrocycle could enhance the interaction strength of the Fe―O bond between the O2 molecule or the intermediate OOHspecies and Fe in the Fe-N4 structure, resulting in a significant decrease in the O―O bond energy, and may help in bond breaking in subsequent reactions, facilitating the ORR process.

Key words: Oxygen reduction reaction, Non-precious metal catalyst, Fe/N/C materials, S-doping, Density functional theory

MSC2000: 

  • O646