Mesoporous carbon based non-precious metal catalysts for oxygen reduction reaction: Effect of metal species and valence state

Abstract

In this work, mesoporous carbon decorated by non-precious metals (FeSO4, Fe2(SO4)3 and CoSO4) have been successfully prepared using a simple one-pot process. A low-cost and easily available nitrogen-containing polymer [poly(ethyleneimine), (PEI)] was chosen as carbon precursor, and nano-silica was employed as a template to provide a large specific area and abundant active sites for the catalyst. The FeSO4-PEI was found to exhibit excellent ORR activity in 0.1 M KOH in terms of onset potential and half wave potential of 0.178V and 0.05V (vs. SHE), respectively. FeSO4-PEI also shows remarkable ORR performance even in 0.5 M H2SO4 with an onset potential and a half wave potential of 0.807V and 0.654V (vs. SHE), respectively. Durability test demonstrates that the FeSO4-PEI only has a small negative shift about 19 mV in 0.1 M KOH and 30 mV in 0.5 M H2SO4 aqueous solution, suggesting an outstanding stability for oxygen reduction. Combined with the physical characterizations of SEM-EDS, XRD, XPS and N2 adsorption-desorption isotherm, FeSO4 verifies strong ability to complex with PEI, which formed more efficient active sites when compared to Fe2(SO4)3-PEI and CoSO4-PEI catalysts. The good catalytic properties could be attributed to the unique nature of metal species, the high specific surface area and the favorable degree of graphitization.