Strontium doped Fe-based porous carbon for highly efficient electrocatalytic ORR and MOR reactions.

ABSTRACT

The catalytic activity improvement of Fe-based active sites derived from metal organic frameworks toward oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) remains a major challenge. In this study, the growth of strontium decorated 2-methylimidazole zinc salt (Sr/ZIF-8) is prepared as a carrier to vapor deposited iron formation Sr doped Fe-based nitrogen-doped carbon framework (named as Sr/FeNC). After high-temperature pyrolysis and vapor deposition, strontium carbonate nanocrystals are evenly dispersed on the shrunk dodecahedron carbon frame and multitudinous Fe-based active catalytic sites are embedded in carbon skeleton. The optimal Sr/FeNC-2 catalyst demonstrates the outstanding ORR performance in terms of a half-wave potential of 0.851 V and an onset potential of 0.90 V, while Sr/FeNC-2 exhibits a high current density of 18.2 mA cm-2 and a lower Tafel slope of 21 mV dec-1 in MOR. The exceptional catalytic activity could be ascribed to the synergistic coupling effect of strontium compounds with Fe-based catalytic sites (Fe-Nx, Fe, and iron oxide). In particular, the formation of SrCO3 affects the bonding configuration of the iron species sites, leading to an optimization of the electronic structure within the multihole carbon matrix. The synthetic approach presents a prospective strategy for future endeavors in developing innovative and advanced bifunctional catalysts for ORR and MOR.