The development and synthesis of cathode electrocatalysts with high activity and durable stability for metal-air batteries is an important challenge in the area of electrocatalysis. Herein, we introduce a novel in-situ nitriding and phosphating strategy for producing W₃N₄ and WP from phosphotungstic acid (HPW)-polyaniline-phytic acid-Fe³⁺ organic–inorganic hybrid material. The final material has a three-dimensional porous framework with W₃N₄-WP heterostructures embedded in the carbon matrix (W₃N₄-WP@NPC). As-made materials exhibit exceptional electrocatalytic performance for the oxygen reduction reaction (ORR), with a diffusion-limiting current density of 6.9 mA·cm⁻² and a half-wave potential of 0.82 V. As a Zn-air primary cathode, the W₃N₄-WP@NPC assembled battery can provide a relatively high peak power density (194.2 mW·cm⁻²). As a Zn-air secondary air-cathode, it has great cycling stability over 500 h. This work provides a simple and efficient method for rationally designing high-performance air cathodes from copolymer-anchored polyoxometalates.

The rational design and preparation of promising cathode electrocatalysts with excellent activity and strong stability for metal-air batteries is a huge challenge. In this work, we innovate an approach of combining solvothermal with high-temperature pyrolysis utilizing zeolitic imidazolate framework (ZIF)-8 and ZIF-67 as the template to synthesize a novel hybrid material of hierarchical porous yolk–shell Co-N-C polyhedron nanocatalysts engaged in graphene nanopocket (yolk–shell Co-N-C@GNP). The obtained catalyst exhibits prominent bifunctional electrocatalytic performance for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the alkaline condition, in which the half-wave potential is 0.86 V for ORR, and the over-potential for OER is 0.42 V at 10 mA·cm⁻². The rechargeable aqueous Zn-air battery fabricated with yolk–shell Co-N-C@GNP cathode deliveries an open circuit voltage (OCV) of 1.60 V, a peak power density of 236.2 mW·cm⁻², and excellent cycling stability over 94 h at 5 mA·cm⁻². The quasi-solid-state Zn-air battery (ZAB) using yolk–shell Co-N-C@GNP displays a high OCV of 1.40 V and a small voltage gap of 0.88 V in continuous cycling tests at 2 mA·cm⁻². This work provides a valuable thought to focus attention on the design of high-efficient bifunctional catalysts with hierarchical porous yolk–shell framework and high-density metal active sites for metal-air battery technologies.

Transition metal nitrides and carbides have attracted intensive attentions in metal-air battery application due to their metallic electron transport behavior and high chemical stability toward the oxygen reduction reaction (ORR). Herein, the polyoxometalate@polyaniline composite derived WN-W₂C heterostructured composite (WN-W₂C@pDC) has been fabricated through an in situ nitriding-carbonization strategy, with WN-W₂C nanoparticles implanted on N doped carbon nanorods. As-fabricated WN-W₂C@pDC demonstrates prominent electrocatalytic performance towards ORR and excellent cycling stability in metal-air battery, which possesses positive half-wave potential and large diffusion limiting current density (0.81 V and 5.8 mA·cm⁻²). Moreover, it demonstrates high peak power density of 157.4 mW·cm⁻² as Al-air primary cathode and excellent stability at the discharge–charge test (> 500 h) of Zn-air secondary battery. The excellent activity and durability of WN-W₂C@pDC catalyst should be attributed to the combined effect of intimate WN-W₂C heterointerfaces, unique embedded nanoparticles structure, and excellent electrical media of N doped carbon, confirmed by a series of contrast experiments.