Interfacial Engineering of Co3 O4 /Fe2 O3 Nano-Heterostructure Toward Superior Li-O2 Batteries.

A major issue with Li-O2 batteries is their slow oxygen reduction and evolution kinetics, necessitating catalysts with high catalytic activity to improve reaction kinetics and cycle stability. Herein, a nano-heterostructured catalyst composed of Co3 O4 and Fe2 O3 (Co3 O4 /Fe2 O3 ) with a porous rod morphology is achieved through an interfacial engineering strategy by constructing Fe2 O3 on the Co3 O4 surface, which can function as a high-performance cathode in order to efficiently encourage the oxygen reduction and evolution while also reduce the battery polarization during charging and discharging. The density functional theory (DFT) calculations show the differences in charge density at the interface of nano-heterostructures, demonstrating the occurrence of an electron transfer process in the interface region of Co3 O4 and Fe2 O3 , implying a strong electronic coupling transfer, and in turn changing the electronic structure of the Co3 O4 . This significantly reduces the adsorption energy of LiO2 intermediates, thereby effectively lowering the overpotential. The resultant Li-O2 battery has larger discharge specific capacity, lower overpotential for the efficient oxygen evolution/reduction, as well as good cycling stability of 280 cycles. This work demonstrates an effective method to fabricate the nano-heterostrucutred materials with enhanced catalytic efficiency for advanced energy applications.

Defect-Engineered Co3 O4 @Nitrogen-Deficient Graphitic Carbon Nitride as an Efficient Bifunctional Electrocatalyst for High-Performance Metal-Air Batteries.

The ability to craft high-efficiency and non-precious bifunctional oxygen catalysts opens an enticing avenue for the real-world implementation of metal-air batteries (MABs). Herein, Co3 O4 encapsulated within nitrogen defect-rich g-C3 N4 (denoted Co3 O4 @ND-CN) as a bifunctional oxygen catalyst for MABs is prepared by graphitizing the zeolitic imidazolate framework (ZIF)-67@ND-CN. Co3 O4 @ND-CN possesses superb bifunctional catalytic performance, which facilitates the construction of high-performance MABs. Concretely, the rechargeable zinc-air battery based on Co3 O4 @ND-CN shows a superior round-trip efficiency of ≈60% with long-term durability (over 340 cycles), exceeding the battery with the state-of-the-art noble metals. The corresponding lithium-oxygen battery using Co3 O4 @ND-CN exhibits an excellent maximum discharge/charge capacity (9838.8/9657.6 mAh g-1 ), an impressive discharge/charge overpotential (1.14 V/0.18 V), and outstanding cycling stability. Such compelling electrocatalytic processes and device performances of Co3 O4 @ND-CN originate from concurrent compositional (i.e., defect-engineering) and structural (i.e., wrinkled morphology with abundant porosity) elaboration as well as the well-defined synergy between Co3 O4 and ND-CN, which produce an advantageous surface electronic environment corroborated by theoretical modeling. By extension, a rich diversity of other metal oxides@ND-CN with adjustable defects, architecture, and enhanced activities may be rationally designed and crafted for both scientific research on catalytic properties and technological development in renewable energy conversion and storage systems.

Toward highly efficient bifunctional electrocatalysts for zinc-air batteries: from theoretical prediction to a ternary FeCoNi design.

3d Transition-metal nitrogen-carbon nanocomposites (T-N-C, T = Fe, Co, Ni, etc.) with highly active M-Nx sites have received much attention in the field of rechargeable zinc-air battery research. However, how to rationally dope metallic elements to decorate T-N-C catalysts and enhance their electrocatalytic performances remains unclear. Herein, we demonstrated that cobalt-doped Fe-rich catalysts are effective in improving ORR performances by density functional theory (DFT) calculations. On this basis, we reported a kind of novel bifunctional electrocatalyst of hollow nitrogen-doped carbon tubes with coexisting M-N-C single atoms and alloy nanoparticles (denoted FexCoyNiz@hNCTs). Benefiting from the synergistic effect between different components, the as-prepared Fe4Co1Ni2@hNCT catalyst exhibited a small overpotential difference of 0.75 V between an OER potential at 10 mA cm-2 and an ORR half-wave potential, as well as an excellent zinc-air battery performance, when serving as the air cathode. This work provided a scalable design concept for multi-metal doping toward high-performance T-N-C electrocatalysts.