Single-Atom Iron Catalysts on Overhang-Eave Carbon Cages for High-Performance Oxygen Reduction Reaction.

Single-atom catalysts have drawn great attention, especially in electrocatalysis. However, most of previous works focus on the enhanced catalytic properties via improving metal loading. Engineering morphologies of catalysts to facilitate mass transport through catalyst layers, thus increasing the utilization of each active site, is regarded as one appealing way for enhanced performances. Herein, as a proof-of-concept research, we design, for the first time, an overhang-eave structure decorated with isolated single-atom iron sites via a silica-mediated MOF-templated (SMMT) approach for oxygen reduction reaction (ORR) catalysis. This catalyst demonstrates superior ORR performances in both alkaline and acidic electrolytes, comparable to the state-of-the-art Pt/C catalyst and superior to most of the precious-metal-free catalysts reported to date. This superior activity originates from its edge-rich structure, having more three-phase boundaries with enhanced mass transport of reactants to accessible single-atom iron sites (that is, increasing the utilization of active sites), which verifies the practicability of such synthetic approach .