The large-scale fabrication of highly efficient and low-cost bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is critical to the development of rechargeable zinc-air batteries (ZABs). Herein, a scalable dealloying strategy was proposed to obtain hierarchically porous spinel-type oxide with minor hereditary Al doping. Benefiting from the well-structured porosity and native dopant, O-np-Ni 5 Co 10 (Al), namely AlÀ NiCo 2 O 4 , exhibited excellent electrocatalytic ORR and OER activities, giving a small potential gap of 0.71 V. The rechargeable ZAB with O-np-Ni 5 Co 10 (Al) as cathode catalyst delivered a high specific capacity of 757 mAh g À 1 , a competitive peak power density of 142 mW cm À 2 , and a long-term discharge-charge cycling stability. Furthermore, density functional theory calculations evidenced that appropriate Al doping into NiCo 2 O 4 could significantly reduce the Gibbs free energy difference to 1.71 eV. This work is expected to inspire the design of performance-oriented bifunctional electrocatalysts for wider applications in renewable energy systems.

It is well known that the oxygen evolution reaction (OER) is predominant to restrict hydrogen production efficiency from water splitting. Herein, a porous spinel oxide, CuCo 2 O 4 , with abundant defects is successfully developed via a facile strategy (alloying−dealloying−annealing) as an efficient and economical electrocatalyst for OER. Profiting from the well-structured porosity, cation defects (Cu vacancies) induced by hereditary Mn doping, and anion defects (oxygen vacancies), O V -np-Cu 10 Co 20 (Mn) gives a smaller OER overpotential of 310 mV at 10 mA cm −2 and admirable long-term stability. Under the simulated industrial conditions (60 °C, 6 M KOH), this demands a cell voltage of 1.71 V to reach 500 mA cm −2 , as well as exhibits a slight attenuation of voltage after a chronopotentiometric test over 80 h. Density functional theory (DFT) calculations uncover that Mn doping could elongate the Cu−O bond, increase the electronic states near the Fermi level, and optimize the d-band center position of CuCo 2 O 4 . With the help of moderate oxygen vacancies (O V ), the energy barrier of the rate-determining step can be further reduced to 2.69 eV. This work tactfully takes advantage of the Mn element to not only construct nanoporous skeletons but also modulate electronic structures, paving an easy route to fabricate defect-enriched porous spinel oxides and accelerate the exploitation of the cost-effective OER electrocatalyst.

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