Metalloporphyrin MOF-derived Ni-doped CO3O4 embedded CeO2-Co3O4 heterostructures as highly efficient and durable bifunctional ORR/OER catalysts for zinc-air batteries

• Heterostructured Ni-Co 3 O 4 /CeO 2 -Co 3 O 4 enhances ORR/OER kinetics • MOF-derived Ni-Co 3 O 4 boosts Co 2+ /Co 3 ratio and oxygen vacancies • RZABs achieve 808 mAh g -1 capacity, 396 mW cm -2 with stable cycling • Operando XAS confirms controlled local distortion and structural integrity Herein, a multifunctional strategy for the synchronous synthesis of Ni-Co 3 O 4 nanoparticles embedded onto CeO 2 -Co 3 O 4 sheet-like microstructures is employed to enhance structural/interface stability and improve ORR/OER electrocatalytic efficiency for zinc-air batteries. Characterization analyses confirm that the increased Co 2+ /Co 3 ratio induced by Ni doping Co 3 O 4 promotes oxygen vacancies, integrating with multiple active sites from CeO 2 -Co 3 O 4 . As results, the composites reveal outstanding catalytic performance, delivering an ORR onset potential of 0.98 V and a half-wave potential of 0.81 V (vs. RHE), along with an OER potential of 1.68 V (vs. RHE) at 10 mA cm -2 which are comparable to Pt/c and RuO 2 . In addition, rechargeable ZABs, using the bifunctional catalyst of Ni-Co 3 O 4 /CeO 2 -Co 3 O 4 composites, can achieve a high capacity of 808 mAh g -1 at 1.0 mA cm -2 , maximum power densities of 396 mW cm -2 at 600 mA cm -2 , and high cycling stability over 120 h. Operando XAS during charge/discharge process verifies that the heterostructure composites enhance structural robustness and enable more controlled redox-induced local distortions.