Double coordination shell modulation of nitrogen-free atomic manganese sites for enhancing oxygen reduction performance.

The rational design and fabrication of the active sites of single-atom catalysts (SACs) remains the main breakthrough for efficient electrocatalytic oxygen reduction reaction (ORR). Although metal-nitrogen-carbon (M-N-C) materials have been reported to exhibit good ORR performance, the M-N bond is prone to oxidation and subsequent destruction in Fenton-like reactions. Here, we report a nitrogen-free Mn-based SAC (Mn-SOG-600) anchored on a nitrogen-free graphene substrate, where manganese is bound to four oxygen atoms and one sulfur atom across two different coordination shells.