context: The hybrid Na–air battery was assembled in a sandwich structure. Initially, the anode part of the hybrid Na–air cell was fabricated in a glove box. The metallic sodium was cut and pressed into a sheet with a diameter of 10 mm as the anode, followed by the injection of organic electrolyte (1 M NaClO4 in tetraethylene glycol dimethyl ether) into the anode chamber. The solid electrolyte NASICON was sealed as the separator for the anode and cathode chamber, ensuring that one side of the NASICON was in contact with the organic electrolyte and the other side was exposed to air. The NASICON solid electrolyte was chosen to avoid direct contact between the aqueous electrolyte and Na anode, and specifically allow Na ions to shuttle between the anode and cathode during the reactions. The cathode compartment was built under ambient air by directly immersing the air electrode in the O2-saturated 0.1 M NaOH electrolyte. The as-prepared electrocatalysts coated on NF (diameter 10 mm) were directly used as air cathodes. For comparison, the 20% Pt/C (Macklin) and RuO2 catalysts cast on NF (diameter 10 mm) were prepared with a mass loading of 1 mg cm−2.
answer: air 