Construction of Highly Active Metal-Containing Nanoparticles & FeCo-N4 Composite Sites for Acid Oxygen Reduction Reaction.

Metal-containing nanoparticles (M-NPs) in metal/nitrogen-doped carbon (M-N-C) catalysts have been considered hostile to acid oxygen reduction reaction (ORR). Some works have confirmed that M-NPs can synergistically increase ORR activity in alkaline media. However, the relation between M-NPs and the active sites of metal coordinated with nitrogen (MNx) is hard to be established in acid medium due to the poor stability of M-NPs. Herein, we develop a strategy to successfully construct a new FeCo-N-C catalyst containing the highly active M-NPs and MN4 composite sites (marked as M/FeCo-SAs-N-C). The enhanced catalytic activity and stability of M/FeCo-SAs-N-C is discovered in our systematic experiments. Moreover, theoretical calculation reveals that there is a strong interaction between M-NPs and FeN4 sites, which can favor ORR by activating the O-O bond, thus facilitating a direct 4e- process. Those findings firstly shed light on the highly active M-NPs and FeN4 composite sites for catalyzing acid oxygen reduction reaction, and the relevant reaction mechanism is suggested.