Amino acid-derived non-precious catalysts with excellent electrocatalytic performance and methanol tolerance in oxygen reduction reaction

Abstract

In polymer electrolyte membrane fuel cells (PEMFCs), slow kinetics and high over-potential of oxygen reduction reaction (ORR) can result in a significantly large amount of Pt usage. Thus, non-precious metal (NPM) catalysts, especially, for ORR, that can be utilized instead of Pt-based catalysts, have been intensively studied. Herein, doped carbon nanostructures as NPM catalysts for ORR in an acid medium were synthesized using a template method with nontoxic, eco-friendly cysteine and iron (III) tetramethoxyphenylporphyrin (Fe-TMPP, 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphyrin iron(III) chloride) used as carbon and doping sources, respectively. To obtain the doped mesoporous carbon nanostructure, mixtures of cysteine and Fe-TMPP with intended ratios (CysX/FeZ) were heated under an N2 atmosphere at 900 °C for 3 h. In particular, Cys2/Fe0.3/C synthesized with an appropriate ratio of cysteine and Fe-TMPP showed a relatively high specific surface area and fairly high portion of doped species such as pyridinic and pyrrolic N, thiophenic S, and Fe-Nx. Moreover, Cys2/Fe0.3/C exhibited significantly enhanced ORR activity and stability in 0.5 M H2SO4 and superior tolerance of methanol in 0.5 M H2SO4 in the presence of CH3OH.