Nonpyrolyzed Fe-N Coordination-Based Iron Triazolate Framework: An Efficient and Stable Electrocatalyst for Oxygen Reduction Reaction.

Pyrolyzed base-metal-based metal-organic frameworks (MOFs) with FeN _x coordination are emerging as nonprecious metal catalysts for electrochemical oxygen reduction reaction (ORR). However, surprisingly, nonpyrolyzed MOFs involving Fe-N coordination have not been explored for the ORR. This study concerns the catalytic performance of a semiconducting nonpyrolyzed iron triazolate framework (FeTa ₂ ) for ORR in alkaline electrolyte. The FeTa ₂ catalyst is studied as composites with different amounts of conductive Ketjenblack carbon (KB). The performance of these FeTa ₂ -x KB (x denotes the KB/FeTa ₂ weight ratio) composites by onset and half-wave potentials of ORR appears to be superior to most previously documented nonpyrolyzed MOFs. Characterization by elemental analysis, FTIR spectroscopy, XPS, and cyclic voltammetry suggest that N-Fe ^III -OH ^- sites at the surface of FeTa ₂ function as the catalytic active sites. This FeTa ₂ also shows very stable activity during ORR, as supported by accelerated durability test of the FeTa ₂ -x KB sample (20 000 cycles, ca. 90 h). The framework structure of FeTa ₂ remains intact during the durability test, which would help to explain its excellent catalytic durability. This would be the first study demonstrating efficient and stable ORR catalysis by a nonpyrolyzed Fe-N coordination-based MOF material.
(© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)