Atomically Dispersed Cu Nanostructures with pH-Universal Electrocatalytic Oxygen Reduction Activity for Zn–Air Batteries

Constructing efficient and cost-effective oxygen reduction reaction (ORR) electrocatalysts in wide pH ranges is important for renewable energy storage and conversion devices. As prospective alternatives to commercial Pt/C electrocatalysts, transition-metal (TM) single-atom catalysts (SACs) delivered limited catalytic activity and stability in a wide pH range, especially in acidic and neutral electrolytes. Herein, we demonstrate a general synthesis strategy for preparation of TM SACs via the MgO template-assisted pyrolysis process. The as-prepared atomically dispersed Cu embedded in a 3D porous N,S-doped carbon nanostructure catalyst (CuNSC-3) displays superior ORR activity in wide pH electrolytes due to its unique structure feature of hierarchical porosity for enriched CuN4S2 center active sites. CuNSC-3 delivers small potentials (Ej3) of 0.87, 0.42, and 0.52 V at a current density of −3 mA cm–2 in 0.1 M KOH, 0.5 M H2SO4, and 0.1 M PBS solutions, respectively. Furthermore, the Zn–air battery using CuNSC-3 as air cathodes achieves a power density of 225 mW cm–2 and an energy density of 973.5 Wh kgZn–1, implying its promising application in real energy-related devices. The CuNSC-3 electrocatalysts can pave the way for the development of next-generation Cu-based ORR cathode electrocatalysts in a wide pH range as well as give guidance for diverse clean fuels of practical significance.