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To develop high-performance and low-cost electrocatalysts for the oxygen reduction reaction (ORR) in Al-air batteries, a promising hierarchical porous N,S-codoped carbon architecture with cobalt-nickel-sulphide nanoparticles immobilized inside was prepared using a simple double-phase encapsulation approach (DPEA), followed by a post heat treatment. The integrated hybrid architecture (Ni-Co-S@G/NSC) exhibited not only a comparable onset potential (0.94 V vs. RHE) and half-wave potential (0.86 V vs. RHE) but also a higher discharge voltage plateau (∼1.23 V at discharge current density of 150 mA cm −2 ) with superior stability to the commercial Pt/C catalyst in ORR and the full cell test. A combination of structural characterizations (e.g., XPS, RSS, XRD, SEM, HRTEM, and BET) and electrochemical analyses showed that the high ORR activity of the Ni-Co-S@G/NSC catalyst was attributed to its high surface area and pore volume, proper degree of the graphitization, and high content of active species combined with their synergetic interactions. Our findings show the advantages in utilizing a metal-organic framework with DPEA for designing well-dispersed, highly active and robust N,S-codoped porous carbons immobilized with sulphide NP catalysts for Al-air batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiMn 2 O 4 -based Ni-Mn bimetallic oxides were fabricated. • The Ni-Mn bimetallic oxides access excellent ORR catalytic performance. • The Ni-Mn bimetallic oxides exhibit good discharge performance in Al-air battery. • Ni-Mn-600 has nanorod morphology and high ratio of (Mn3++Mn4+)/Mn2+ and Ni3+/Ni2+. To date, research on air battery catalysts has been mainly focused on finding materials with a high oxygen reduction reaction (ORR) catalytic activity. However, the high cost of platinum catalysts restricts their commercialization. Herein, we report a simple hydrothermal-calcination method to fabricate low-cost NiMn 2 O 4 -based Ni-Mn bimetallic oxides. The Ni-Mn-600 sample showed a high onset potential (1.01 V vs. RHE), which was more positive than that for 20 wt% Pt/C (0.97 V vs. RHE), and its half-wave potential (0.78 V vs. RHE) was comparable to that for 20 wt% Pt/C (0.84 V vs. RHE). Moreover, Ni-Mn-600 as an Al-air battery air–cathode catalyst exhibited a high discharge plateau of 1.42 V and peak power density of 100.45 mW cm−2, which outperformed those for 20 wt% Pt/C (1.34 V and 76.10 mW cm−2). The high ORR electrocatalytic activity of Ni-Mn-600 may be attributed to the nanorod morphology and high ratio of (Mn3++Mn4+)/Mn2+ and Ni3+/Ni2+. This work demonstrated that NiMn 2 O 4 -based Ni-Mn bimetallic oxides as cathode catalysts have good research prospects in aluminum-air batteries and other energy applications. [ABSTRACT FROM AUTHOR]

• Electrospun N,S codoped porous carbon nanofibers with Co 9 S 8 were fabricated. • The free-standing complex fibers used as cathodes in Li-O 2 and Al-air batteries. • Synergistic roles of Co 9 S 8 nanoparticles core and N,S doped graphitic shell. • The superior batteries performances can be attributed to the synergistic effect. The rational design of economical air cathodes or electrocatalysts with high electrocatalytic activity and durability for both non-aqueous lithium-oxygen (Li-O 2) and alkaline electrolyte aluminum-air (Al-air) batteries is a critical factor for promoting the practical applications. Herein, we report the fabrication of graphitic layers covered with Co 9 S 8 nanoparticles immobilized inside N,S dual-doped hierarchical porous carbon nanofibers by a facile and one-step electrospinning method combined with a pyrolytic process. When employed as free-standing electrodes for a Li-O 2 battery and an Al-air battery, the as-prepared Co 9 S 8 @G/NS-PCNFs deliver excellent battery performances and afford comparable catalytic performance as that of a 20 wt% Pt/C electrode. The results show that the superior battery performance of the Co 9 S 8 @G/NS-PCNF cathode can be attributed to the synergistic effect between the catalytic behavior of the uniformly distributed Co 9 S 8 nanoparticles and the textural properties of the N,S dual-doped hierarchical porous carbon nanofibers. Our findings open a new direction for designing nonprecious hybrid metal sulfide carbon architectures to replace costly Pt/C electrodes and indicate their promising application in next-generation metal-air batteries. [ABSTRACT FROM AUTHOR]

• ZIF-67 nanospheres were concatenated by electrospinning. • CoP was confined to N,P-doped carbon by synchronous carbonization/phosphatization. • CoP-decorated N,P-doped carbon shows an excellent oxygen reduction performance. • CoP-decorated N,P-doped carbon endows Al-air batteries with outstanding properties. Transition metal phosphides (TMPs) have attracted increasing attention as robust and efficient catalyst materials owing to their unique electronic properties and stabilities. Here, CoP-decorated N,P-doped necklace-like carbon (CoP@N,P-CNFs) was fabricated by thermal treatment of electrospun ZIF-67 spheres. The resulting CoP exhibits not only fine nanostructures but also synergistic effects with N,P-doped carbon. Polyacrylonitrile-derived nanofibers also promote the conductivity of the complex. As a consequence, CoP@N,P-CNFs exhibited excellent electrocatalytic oxygen reduction activities and Al-air battery performance. It is believed that nanofibers supporting metal-organic framework-derived heteroatom-doped carbon-encapsulated TMPs can be extended to broad applications in energy storage and conversions. [ABSTRACT FROM AUTHOR]