Metal-Organic-Framework-Derived Co-Fe Bimetallic Oxygen Reduction Electrocatalysts for Alkaline Fuel Cells.

The oxygen reduction reaction (ORR) is considered the cornerstone for regenerative energy conversion devices involving fuel cells and electrolyzers. The development of non-precious-metal electrocatalysts is of paramount importance for their large-scale commercialization. Here, Co-Fe binary alloy embedded bimetallic organic frameworks (BMOF)s based on carbon nanocomposites have been designed with a compositionally optimized template, by a facile host-guest strategy, for ORR in alkaline media. The electrocatalyst exhibits promising electrocatalytic activity for ORR with a half-wave potential of 0.89 V in 0.1 M NaOH, comparable to state-of-the-art Pt/C electrocatalysts. More importantly, it exhibits robust durability after 30 000 potential cycles. Scanning transmission electron microscopy (STEM) and quantitative energy-dispersive X-ray (EDX) spectroscopy suggest that the Co-Fe alloy nanoparticles have a homogeneous elemental distribution of Co and Fe at the atomic-scale optimized BMOF and Co/Fe ratio of 9:1. The long-term durability is attributed to its ability to maintain its structural and compositional integrity after the cycling process, as evidenced by STEM-EDX analysis. This work provides valuable insights into the design and fabrication of novel platinum-group-metals-free highly active ORR electrocatalysts in alkaline media.