Three-Dimensional Hierarchical Porous Fe, N-Doped Hollow Carbon Nanospheres as Stable Electrocatalyst for Efficient Oxygen Reduction Reaction in Both Acidic and Alkaline Electrolytes

3D hierarchical porous Fe, N-doped hollow carbon nano-spheres (Fe-N-C HPNCs) as efficient ORR electrocatalyst were obtained using melamine-formaldehyde resin (MF) nanospheres as thermal sacrificial hard template to optimize the pore structure and provide nitrogen source to the catalyst. The optimized Fe-N-C HPNCs catalyst exhibited excellent catalytic activity with onset (E-onset) and half-wave (E-1/2) potential (E-onset=1.07 V; E-1/2=0.90 V vs. RHE) superior to commercial Pt/C catalyst in 0.1 M KOH solution, and demonstrated excellent stability. When applied as cathode electro-catalyst in a Zn-air battery, it produced maximum power density (P-max) of 127 mW cm(-2), which is higher than that of commercial Pt/C (P-max=119 mW cm(-2)). It also showed good activity (E-onset=0.89 V; E-1/2=0.78 V) in 0.1 M HClO4 electrolyte with significantly enhanced stability (Delta E-1/2=-7 mV) relative to the Pt/C catalyst (Delta E-1/2=-27 mV).

Automated summary

Three-dimensional hierarchical porous Fe, N-doped hollow carbon nano-spheres (Fe-N-C HPNCs) were used as efficient ORR electrocatalysts. They exhibited superior catalytic activity and stability compared to commercial Pt/C catalysts, making them suitable for applications in Zn-air batteries.