Hybrid shells of MnO₂ nanosheets encapsulated by N-doped carbon towards nonprecious oxygen reduction reaction catalysts

Developing nonprecious electrocatalysts for efficient oxygen reduction reaction (ORR) have aroused increasing interest recently. Herein, α-MnO₂ nanosheet-based hollow spheres encapsulated by N-doped carbon (denoted as N-Carbon/MnO₂/N-Carbon) as efficient ORR electrocatalysts were reported. As started from redox reactive polystyrene/polyaniline (PS/PANI) core/shell templates, MnO₂ and PANI layers were sequentially in situ loaded, leading to the formation of MnO₂ nanosheet-based hollow spheres encapsulated by PANI (denoted as PANI/MnO₂/PANI) after PS removal process. Finally, the calcination process ensured the crystallization of MnO₂ and carbonization of PANI, resulting in the formation of N-Carbon/MnO₂/N-Carbon hybrid shells. The N-Carbon/MnO₂/N-Carbon hybrid shells showed excellent electrocatalytic activity towards ORR in 0.1 mol L^-1 KOH aqueous solution, making the hybrids promising cathode catalysts for alkaline fuel cell applications.