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

In this work, mesoporous carbon decorated by non-precious metals (FeSO4, Fe-2(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 H(2)SO(4 )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 N-2 adsorption-desorption isotherm, FeSO4 verifies strong ability to complex with PEI, which formed more efficient active sites when compared to Fe-2(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. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.