(475e) Transition-Metal Doped Carbon Electrocatalysts for Oxygen Reduction

Active and durable non-precious metal catalysts (NPMCs) are highly demanded to replace the rare and expensive Pt for the oxygen reduction reaction (ORR) in polymer electroltye fuel cells and metal-air batteris. Compared to extensively studied ORR catalysis in alkaline media, development of high-performance NPMCs to replace Pt in acidic electrolytes remains grand challenges. Great progress has been made over the last decade to develop transition metal-derived nitrogen-doped carbons (M-N-C, M: Fe or Co), the most promising class of NPMC for ORR electrocatalysis. Among studied catalysts, the Fe-N-C formulation holds the greatest promise for the ORR in acid. Here, we report a new highly active and stable Fe-N-C catalyst featured with well-dispersed atomic Fe in porous carbon matrix, which was prepared through one single thermal conversion from Fe-doped ZIF-8, a metal-organic framework (MOF) containing Zn²⁺ and well-defined Fe-N₄ coordination. Unlike other Fe-N-C catalyst preparation, no additional tedious post-treatments such as acid leaching and the second heating treatment are required in this work. Notably, an O₂-free environment for preparing the Fe-doped ZIF-8 precursor is found to be crucial for yielding uniform Fe distribution into highly porous N-doped carbon matrix. The resulting new Fe-N-C catalyst exhibited exceptionally improved ORR activity with a very high half-wave potential (0.82 V vs. RHE) and sufficient potential cycling stability in acid. Opposite to previous observation, the highly active Fe-N-C catalyst is in the absence of any graphitized nanocarbons, which would lead to a new discussion in the field for understanding the role of carbon during the ORR electrocatalysis.