Nano Hexagon NiCeO ₂ for Al–Air Batteries: A Combined Experimental and Density Functional Theory Study of Oxygen Reduction Reaction Activity

Nano hexagon NiCeO 2 is synthesized via a simple one‐pot hydrothermal method and evaluated as a highly efficient electrocatalyst for the oxygen reduction reaction (ORR) in an Al‐air battery (AAB). Structural analysis using X‐ray diffraction reveals peak shifts and lattice contraction, confirming the successful incorporation of Ni into the CeO 2 host matrix. Raman spectroscopy identified a characteristic peak associated with oxygen vacancies, indicating defect formation. Thermogravimetric analysis showed a 4.97% weight gain, likely due to the filling of oxygen vacancies at elevated temperatures. Transmission electron microscope revealed a nano hexagon morphology with an average particle size of 20 nm. X‐ray Photoelectron Spectroscopy analysis confirmed the presence of both cerium and nickel elements. Electronic structure calculations, performed using density functional theory via Quantum ESPRESSO, indicated that Ni doping introduces new 3d states into the CeO 2 band structure, resulting in bandgap narrowing and a lowered Fermi level. Electrochemical testing demonstrated that NiCeO 2 exhibits superior ORR performance compared to commercial Pt/C catalysts. Kinetic analysis suggested a near four‐electron transfer pathway. Durability is assessed using chronoamperometry, showing that NiCeO 2 retained 90% of its initial current after 20 h of operation, outperforming Pt/C. Furthermore, an AAB is constructed using NiCeO 2 as the cathode, which achieved an open circuit voltage of 1.65 V with a discharge capacity of 1070 mAh·g −1 , delivering a notable power density of 77.64 mW·cm −2 . The enhanced ORR activity is attributed to the synergistic interaction between CeO 2 and Ni, which significantly improves the overall performance of the AAB These findings suggest that NiCeO 2 is a promising cathode material for high‐performance AABs.