Oxygen Reduction Electrocatalyst Based on Strongly Coupled Cobalt Oxide Nanocrystals and Carbon Nanotubes

Microwave-assisted synthesis of mesoporous Co3O4 nanoflakes for applications in lithium ion batteries and oxygen evolution reactions

Mesoporous Co3O4 nanoflakes with an interconnected architecture were successfully synthesized using a microwave-assisted hydrothermal and low-temperature conversion method, which exhibited excellent electrochemical performances as anode materials in lithium ion batteries and as catalysts in the oxygen evolution reaction (OER). Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) observations showed the unique interconnected and mesoporous structure. When employed as anode materials for lithium ion batteries, mesoporous Co3O4 nanoflakes delivered a high specific capacity of 883 mAh/g at 0.1C current rate and stable cycling performances even at higher current rates. Post-mortem analysis of ex situ FESEM images revealed that the mesoporous and interconnected structure had been well maintained after long-term cycling. The mesoporous Co3O4 nanoflakes also showed both OER active properties and good catalytic stability. This could be attributed to both the stability of unique mesoporous structure and highly reactive facets.

Co3O4 nanoparticles decorated carbon nanofiber mat as binder-free air-cathode for high performance rechargeable zinc-air batteries

An efficient, durable and low cost air-cathode is essential for a high performance metal-air battery for practical applications. Herein, we report a composite bifunctional catalyst, Co3O4 nanoparticles-decorated carbon nanofibers (CNFs), working as an efficient air-cathode in high performance rechargeable Zn-air batteries (ZnABs). The particles-on-fibers nanohybrid materials were derived from electrospun metal-ion containing polymer fibers followed by thermal carbonization and a post annealing process in air at a moderate temperature. Electrochemical studies suggest that the nanohybrid material effectively catalyzes oxygen reduction reaction via an ideal 4-electron transfer process and outperforms Pt/C in catalyzing oxygen evolution reactions. Accordingly, the prototype ZnABs exhibit a low discharge-charge voltage gap (e.g. 0.7 V, discharge-charge at 2 mA cm(-2)) with higher stability and longer cycle life compared to their counterparts constructed using Pt/C in air-cathode. Importantly, the hybrid nanofiber mat readily serves as an integrated air-cathode without the need of any further modification. Benefitting from its efficient catalytic activities and structural advantages, particularly the 3D architecture of highly conductive CNFs and the high loading density of strongly attached Co3O4 NPs on their surfaces, the resultant ZnABs show significantly improved performance with respect to the rate capability, cycling stability and current density, promising good potential in practical applications.

Graphene-based transition metal oxide nanocomposites for the oxygen reduction reaction

The development of low cost, durable and efficient nanocatalysts to substitute expensive and rare noble metals (e.g. Pt, Au and Pd) in overcoming the sluggish kinetic process of the oxygen reduction reaction (ORR) is essential to satisfy the demand for sustainable energy conversion and storage in the future. Graphene based transition metal oxide nanocomposites have extensively been proven to be a type of promising highly efficient and economic nanocatalyst for optimizing the ORR to solve the world-wide energy crisis. Synthesized nanocomposites exhibit synergetic advantages and avoid the respective disadvantages. In this feature article, we concentrate on the recent leading works of different categories of introduced transition metal oxides on graphene: from the commonly-used classes (FeOx, MnOx, and CoOx) to some rare and heat-studied issues (TiOx, NiCoOx and Co-MnOx). Moreover, the morphologies of the supported oxides on graphene with various dimensional nanostructures, such as one dimensional nanocrystals, two dimensional nanosheets/nanoplates and some special multidimensional frameworks are further reviewed. The strategies used to synthesize and characterize these well-designed nanocomposites and their superior properties for the ORR compared to the traditional catalysts are carefully summarized. This work aims to highlight the meaning of the multiphase establishment of graphene-based transition metal oxide nanocomposites and its structural-dependent ORR performance and mechanisms.

Graphene-supported iron-based nanoparticles encapsulated in nitrogen-doped carbon as a synergistic catalyst for hydrogen evolution and oxygen reduction reactions

Electrolyzers and fuel cells have been extensively investigated as promising solutions for renewable energy storage and conversion. Hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) are important electrocatalytic processes in electrolyzers and fuel cells. Exploring efficient non-precious metal catalysts for HER and ORR in acidic medium remains a great challenge. Herein, we report that graphene-supported iron-based nanoparticles encapsulated in a nitrogen-doped carbon (Fe@N-C) hybrid material acts as an efficient HER and ORR catalyst. The hybrid material was synthesized by pyrolysis of graphene oxide and ammonia ferric citrate followed by acid-leaching. During the pyrolysis, nitrogen was doped into a graphene lattice, and the carbon nanoshell grown on graphene effectively suppressed the stacking of graphene sheets, exposing more active sites to reactants. The hybrid material showed higher electrocatalytic activities than graphene sheets or Fe@N-C alone, which is probably attributed to the synergetic role of nitrogen-doped graphene and Fe@N-C towards the electrocatalytic reactions.

Carbon nanotubes and catalysis: the many facets of a successful marriage

Carbon nanotubes have emerged as unique carbon allotropes that bear very interesting prospects in catalysis.

Nitrogen-doped graphene/carbon nanotube/Co3O4 hybrids: one-step synthesis and superior electrocatalytic activity for the oxygen reduction reaction

N-rGO/CNTs/Co₃O₄ hybrids were prepared through a simple one-step hydrothermal method, and exhibited comparable electrocatalytic ORR activity to Pt/C catalysts, excellent tolerance to methanol crossover effects, and even better long-term stability.

High-performance nickel manganese ferrite/oxidized graphene composites as flexible and binder-free anodes for Li-ion batteries

The obtained binder-free and flexible free-standing Ni_0.5Mn_0.5Fe₂O₄/oxidized graphene (NMFO/OGP) and NMFO/OGP coated on polypropylene microporous film exhibited good electrochemical performance.

Facile fabrication of sandwich-structured Co3O4/N-rGO/AB hybrid with enhanced ORR electrocatalytic performances for metal–air batteries

We have rationally designed and facilely synthesized Co₃O₄/N-rGO/acetylene black with remarkable electrocatalytic activity and durability for ORR.

Recent advancements in Pt and Pt-free catalysts for oxygen reduction reaction

Based on the understanding of the ORR catalytic mechanism, advanced Pt-based and Pt-free catalysts have been explored.

Confined platinum nanoparticle in carbon nanotube: structure and oxidation

Confined metal particles show unexpected structural versatility, leading to higher stability and better catalytic performance, as predicted from first-principles-based global optimization methods.

Hybrids based on transition metal phosphide (Mn2P, Co2P, Ni2P) nanoparticles and heteroatom-doped carbon nanotubes for efficient oxygen reduction reaction

Hybrids based on transition metal phosphide (Mn₂P, Co₂P, Ni₂P) nanoparticles and heteroatom-doped carbon nanotubes were facilely synthesized, and used as efficient oxygen reduction reaction (ORR) catalysts in alkaline solution.

Carbon nanotube catalysts: recent advances in synthesis, characterization and applications

Carbon nanotubes are promising materials for various applications.

Thermal evolution of cobalt deposits on Co3O4(111): atomically dispersed cobalt, two-dimensional CoO islands, and metallic Co nanoparticles

Cobalt deposition onto Co₃O₄(111) leads to formation of atomically dispersed cobalt species, which form ordered two-dimensional oxide islands upon annealing.

Titanium oxynitride interlayer to influence oxygen reduction reaction activity and corrosion stability of Pt and Pt-Ni alloy

A key advancement target for oxygen reduction reaction catalysts is to simultaneously improve both the electrochemical activity and durability. To this end, the efficacy of a new highly conductive support that comprises of a 0.5 nm titanium oxynitride film coated by atomic layer deposition onto an array of carbon nanotubes has been investigated. Support effects for pure platinum and for a platinum (50 at %)/nickel alloy have been considered. Oxynitride induces a downshift in the d-band center for pure platinum and fundamentally changes the platinum particle size and spatial distribution. This results in major enhancements in activity and corrosion stability relative to an identically synthesized catalyst without the interlayer. Conversely, oxynitride has a minimal effect on the electronic structure and microstructure, and therefore, on the catalytic performance of platinum-nickel. Calculations based on density functional theory add insight with regard to compositional segregation that occurs at the alloy catalyst-support interface.

Co3O4 nanoparticles/cellulose nanowhiskers-derived amorphous carbon nanoneedles: sustainable materials for supercapacitors and oxygen reduction electrocatalysis

Amorphous carbon nanoneedles-supported Co₃O₄ nanoparticles, materials that have electrocatalytic activity for ORR and the ability to store charges, are synthesized with nanoreactors using Co(ii) ions and cellulose nanowhiskers as precursor.

Strong-coupled Co-g-C3N4/SWCNTs composites as high-performance electrocatalysts for oxygen reduction reaction

A high performance electrocatalyst for ORR in alkaline is based on the strong coupling of Co-g-C₃N₄ derived active sites on SWCNTs.

Sulfur-doped porous carbon nanosheets as high performance electrocatalysts for PhotoFuelCells

New sulfur-doped highly porous carbon nanosheets applicable as electrocatalysts in PhotoFuelCells.

Spinel nickel ferrite nanoparticles strongly cross-linked with multiwalled carbon nanotubes as a bi-efficient electrocatalyst for oxygen reduction and oxygen evolution

NiFe₂O₄ nanoparticles successfully cross-linked with the outer walls of MWCNTs demonstrate excellent catalytic activities and stabilities for both the ORR and OER compared to commercial Pt/C, owing to the strong coupling and synergistic effects.

MnNiCoO4/N-MWCNT nanocomposite catalyst with high selectivity in membraneless direct formate fuel cells and bifunctional activity for oxygen electrochemistry

A nanocomposite electrocatalyst MnNiCoO₄/N-MWCNT exhibits the desired catalytic selectivity for the development of membraneless direct formate fuel cells.

Cobalt nanoparticles embedded in N-doped carbon as an efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions

Cobalt based catalysts are promising bifunctional electrocatalysts for both oxygen reduction and oxygen evolution reactions (ORR and OER) in unitized regenerative fuel cells (URFCs) operating with alkaline electrolytes. Here we report a hybrid composite of cobalt nanoparticles embedded in nitrogen-doped carbon (Co/N-C) via a solvothermal carbonization strategy. With the synergistic effect arising from the N-doped carbon and cobalt nanoparticles in the composite, the Co/N-C hybrid catalyst exhibits highly efficient bifunctional catalytic activity and excellent stability toward both ORR and OER. The ΔE (oxygen electrode activity parameter for judging the overall electrocatalytic activity of a bifunctional electrocatalyst) value for Co/N-C is 0.859 V, which is smaller than those of Pt/C and most of the non-precious metal catalysts in previous studies. Furthermore, the Co/N-C composite also shows better bifunctional catalytic activity than its oxidative counterparts, which could be attributed to the high specific surface area and the efficient charge transfer ability of the composite, as well as the good synergistic effect between N-doped carbon and the Co nanoparticles in the Co/N-C composite.

Binder-free carbon nanotube electrode for electrochemical removal of chromium

Electrochemical treatment of chromium-containing wastewater has the advantage of simultaneously reducing hexavalent chromium (CrVI) and reversibly adsorbing the trivalent product (CrIII), thereby minimizing the generation of waste for disposal and providing an opportunity for resource reuse. The application of electrochemical treatment of chromium is often limited by the available electrochemical surface area (ESA) of conventional electrodes with flat surfaces. Here, we report the preparation and evaluation of carbon nanotube (CNT) electrodes consisting of vertically aligned CNT arrays directly grown on stainless steel mesh (SSM). We show that the 3-D organization of CNT arrays increases ESA up to 13 times compared to SSM. The increase of ESA is correlated with the length of CNTs, consistent with a mechanism of roughness-induced ESA enhancement. The increase of ESA directly benefits CrVI reduction by proportionally accelerating reduction without compromising the electrode's ability to adsorb CrIII. Our results suggest that the rational design of electrodes with hierarchical structures represents a feasible approach to improve the performance of electrochemical treatment of contaminated water.

Multifunctional electroactive heteroatom-doped carbon aerogels

The design and synthesis of highly active, durable, and cheap nanomaterials for various renewable energy storage and conversion applications is extremely desirable but remains challenging. Here, a green and efficient strategy to produce CoOx nanoparticles and surface N-co-doped carbon aerogels (Co-N-CAs) is reported by multicomponent surface self-assembly of commercially melamine sponge (CMS). In the methodology, the CMS simultaneously function as green N precursor for surface N doping and 3D support. The resulting Co-N-CAs exhibit 3D hierarchical, interconnected macro- and bimodal meso-porosity (6.3 nm and <4 nm), high surface area (1383 m(2) g(-1)), and highly dispersed, semi-exposured CoOx nanoparticles (diameter of 12.5 nm). The surface doping of N, semi-exposured configuration of CoOx nanoparticles and the penetrated complementary pores (<4 nm) in the carbon walls provide highly accessibility between electroactive components and electrolytes to improve reactivity. With their tailored architecture, the Co-N-CAs show superior electrocatalytic oxygen reduction (ORR) activities comparable to the commercially Pt/C catalysts, high specific capacitance (433 F g(-1)), excellent lithium storage (938 mAh g(-1)), and outstanding durability, making them very promising for advanced energy conversion and storage. In addition, the presented strategy can be extended to fabricate other metal oxide- and N-co-doped carbon aerogels for diverse energy-related applications.

Enhanced electrocatalytic performance for oxygen reduction via active interfaces of layer-by-layered titanium nitride/titanium carbonitride structures

Cathode materials always limit the performance of fuel cells while the commercial platinum-based catalysts hardly meet the requirements of low cost, durable and stable. Here a non-precious metal oxygen reduction reaction (ORR) electocatalyst based on titanium nitride/titanium carbonitride hierarchical structures (TNTCNHS) is demonstrated as high activity as Pt/C. In alkaline condition, tuning interface/mass ratio of TiN/TiCN, we observed the onset potential of ~0.93 V vs. RHE and a limit diffusion current density of ~5.1 mA cm⁻² (at a rotating speed of 1600 rpm) on TNTCNHS with a relative low catalyst loading of ~0.1 mg cm⁻². The kinetic current, durability and tolerance to crossover effect studies reveal even more efficient than carbon-supported platinum. The architecture fabrication for such electrocatalyst is easy to realize in industrial-scale facilities, for the use of chemical vapor deposition (CVD) technique could support a huge area production (more than 10000 cm² for one pot) to satisfy the enormous market requirements in the future.

Nitrogen-doped mesoporous graphene as a synergistic electrocatalyst matrix for high-performance oxygen reduction reaction

To balance the anchoring sites and conductivity of the catalyst supports is a dilemma in electrocatalytic oxygen reduction reaction (ORR). Nitrogen-doped mesoporous graphene (N-MG) with large surface area, high porosity, and superior intrinsic conductivity has been developed to address this issue. Using N-MG as the backbone, a hybrid catalyst of Co3O4 nanocrystals embedded on N-MG (Co3O4/N-MG) was prepared for the electrocatalytic ORR in alkaline media. The Co3O4/N-MG showed high catalytic activity for the four-electron ORR, giving a more positive onset potential (0.93 V vs RHE) and a higher current density. The unique property of N-MG and the synergetic effect of Co3O4 and N-MG are prominent for ORR. With improved electrocatalytic activity and durability, the Co3O4/N-MG can be an efficient nonprecious metal catalyst and potentially used to substitute the platinum-based cathode catalysts in fuel cells and metal-air batteries.

Co3O4 nanowires supported on 3D N-doped carbon foam as an electrochemical sensing platform for efficient H2O2 detection

Using a simple hydrothermal procedure and a subsequent annealing treatment, one-dimensional (1D) cobalt oxide nanowires (Co3O4-NWs) with tunable size have been successfully in situ fabricated on a three-dimensional (3D) carbon foam (CF) network. By changing the hydrothermal treatment time (0.5, 1, or 2 h) at 180 °C, size-controlled Co3O4 nanowires can be formed on the CF. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) measurements showed that nanoporous Co3O4 nanowires grew uniformly on the 3D carbon framework. Because of the 3D porous architecture and the high conductivity of the carbon foam skeleton, the obtained composites are characterized by fast mass transport, large surface area and high electronic conductivity, which make them very promising electrochemical sensing materials. Among the studied composites, the Co3O4-NWs/CF hydrothermally treated for 1 h exhibited the lowest detection limit (1.4 μM) and the largest linear ranges (0.01-1.4 mM) with a sensitivity of 230 nA μM(-1) cm(-2) for H2O2 detection. The present study shows that metal oxides supported on 3D carbon materials present a class of promising sensing platform for the electrochemical detection of H2O2.

Nickel-based thin film on multiwalled carbon nanotubes as an efficient bifunctional electrocatalyst for water splitting

Herein, we report electrodeposited nickel-based thin film (NiOx) on multiwalled carbon nanotubes (MWCNTs) as a highly efficient bifunctional catalyst for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Under reductive conditions (-1.2 V vs Ag/AgCl), the hydrogen evolution catalyst (H2-NiO(x)) was facilely deposited on MWCNTs. The resulting film demonstrates good catalytic activity for hydrogen production in a near-neutral aqueous solution at low overpotential. When switched to oxidative conditions (+1.1 V vs Ag/AgCl), the amorphous H2-NiO(x) film onto MWCNTs can be transformed into another amorphous material (O2-NiO(x)) to efficiently catalyze OER. The NiO(x)-MWCNTs catalyst was further characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). The results show that the content of oxygen in the O2-NiO(x)-MWCNTs film is higher than that in the H2-NiO(x)-MWCNTs film. The NiOx-MWCNTs catalyst has good catalytic stability, and the film is reversible when the potentials are switched between the reductive conditions and oxidative conditions. The Faradaic efficiencies of hydrogen and oxygen production are >95%.

Facile synthesis of Co₃O₄@CNT with high catalytic activity for CO oxidation under moisture-rich conditions

The catalytic oxidation reaction of CO has recently attracted much attention because of its potential applications in the treatment of air pollutants. The development of inexpensive transition metal oxide catalysts that exhibit high catalytic activities for CO oxidation is in high demand. However, these metal oxide catalysts are susceptible to moisture, as they can be quickly deactivated in the presence of trace amounts of moisture. This article reports a facile synthesis of highly active Co3O4@CNT catalysts for CO oxidation under moisture-rich conditions. Our synthetic routes are based on the in situ growth of ultrafine Co3O4 nanoparticles (NPs) (∼2.5 nm) on pristine multiwalled CNTs in the presence of polymer surfactant. Using a 1% CO and 2% O2 balanced in N2 (normal) feed gas (3-10 ppm moisture), a 100% CO conversion with Co3O4@CNT catalysts was achieved at various temperatures ranging from 25 to 200 °C at a low O2 concentration. The modulation of surface hydrophobicity of CNT substrates, other than direct surface modification on the Co3O4 catalytic centers, is an efficient method to enhance the moisture resistance of metal oxide catalysts for CO oxidation. After introducing fluorinated alkyl chains on CNT surfaces, the superhydrophobic Co3O4@CNT exhibited outstanding activity and durability at 150 °C in the presence of moisture-saturated feed gas. These materials may ultimately present new opportunities to improve the moisture resistance of metal oxide catalysts for CO oxidation.

A comparative study of composition and morphology effect of Ni(x)Co(1-x)(OH)2 on oxygen evolution/reduction reaction

Oxygen electrochemistry has been intensely studied in the pursuit of sustainable and efficient energy conversion and storage solutions. Over the years, developing oxygen electrode catalysts with high activity and low cost remains a great challenge, despite tremendous efforts. Here, NixCo1-x(OH)2 is used as a bifunctional electrocatalyst for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The effect of its compositions (x = 1, 0.55, 0) and morphologies (including both multilayer and single-layer NixCo1-x(OH)2) on catalytic activity is studied systematically in order to optimize the oxygen-electrochemical performance of 3d-M (M = Ni and Co) metal hydroxides. Our results show that the compositions of NixCo1-x(OH)2 has a great influence on overpotentials by comparing multilayer Co(OH)2, Ni0.55Co0.45(OH)2, and Ni(OH)2 for OER. Multilayer Ni(OH)2 exhibits the lowest overpotential of 324 mV at the current density of 5 mA/cm(2). Moreover, the overpotential could be greatly lowered by using single-layer NixCo1-x(OH)2. Single-layer Ni(OH)2 nanosheet manifests 71 mV overpotential decrease (5 mA/cm(2)) and a factor of 14 turnover frequency increase as compared to multilayer Co(OH)2 for OER. As for ORR, multilayer Co(OH)2 shows the best activity among multilayer NixCo1-x(OH)2. Similar to OER, single-layer NixCo1-x(OH)2 demonstrates enhanced ORR activity over multilayer NixCo1-x(OH)2. Single-layer Co(OH)2 exhibits the best catalytic activity and 3.7 electrons are transferred during oxygen reduction process. The successful identification of the composition and morphology effect of 3d metal hydroxides on electrocatalytic performance provides the foundation for rational design of active sites for high-performance catalyst for both OER and ORR.

Flexible nitrogen-doped graphene/carbon nanotube/Co3O4 paper and its oxygen reduction activity

Due to the demand of an efficient, inexpensive and scalable synthesis of oxygen reduction reaction (ORR) catalyst for practical application in fuel cell, we demonstrate a facile strategy to fabricate the flexible nitrogen-doped graphene/carbon nanotube/Co3O4 (NG/CNT/Co3O4) paper catalyst. In the hydrothermal process, the in situ formation of Co3O4 nanoparticles, reduction of GO and doping of nitrogen species occur simultaneously in the assembled paper in ammonia solution. Because of the synergistic effects of three active components and the spacing effect of CNTs and Co3O4 nanoparticles on avoiding the re-aggregation of assembled graphene nanosheets, the free-standing NG/CNT/Co3O4 paper exhibits an enhanced ORR catalytic performance with stable durability and strong methanol-tolerant capability, indicating promising potential as ORR electrocatalyst in practical applications.

Nitrogen-doped porous carbon/Co3O4 nanocomposites as anode materials for lithium-ion batteries

A simple and industrially scalable approach to prepare porous carbon (PC) with high surface areas as well as abundant nitrogen element as anode supporting materials for lithium-ion batteries (LIBs) was developed. Herein, the N-doped PC was prepared by carbonizing crawfish shell, which is a kind of food waste with abundant marine chitin as well as a naturally porous structure. The porous structure can be kept to form the N-doped PC in the pyrolysis process. The N-doped PC-Co3O4 nanocomposites were synthesized by loading Co3O4 on the N-doped PC as anode materials for LIBs. The resulting N-doped PC-Co3O4 nanocomposites release an initial discharge of 1223 mA h g(-1) at a current density of 100 mA g(-1) and still maintain a high reversible capacity of 1060 mA h g(-1) after 100 cycles, which is higher than that of individual N-doped PC or Co3O4. Particularly, the N-doped PC-Co3O4 nanocomposites can be prepared in a large yield with a low cost because the N-doped PC is derived from abundant natural waste resources, which makes it a promising anode material for LIBs.

Strongly coupled NiCo(2)O(4)-rGO hybrid nanosheets as a methanol-tolerant electrocatalyst for the oxygen reduction reaction

Strongly coupled NiCo2 O4 -rGO hybrid nanosheets are syntheiszed through a cost-effective two-step strategy involving a facile polyol process and subsequent thermal annealing treatment in air. The hybrid nanosheets exhibit impressive electrocatalytic performance for the oxygen reduction reaction (ORR) with a current density and onset potential comparable to those of commercial Pt/C catalyts, while having perfect tolerance to methanol..

Hierarchical nanostructured NiCo2O4 as an efficient bifunctional non-precious metal catalyst for rechargeable zinc-air batteries

A nickel-doped cobalt oxide spinel structure is a promising non-precious metal electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal-air batteries and water electrolyzers operating with alkaline electrolytes. One dimensional NiCo2O4 (NCO) nanostructures were prepared by using a simple electrospinning technique with two different metal precursors (metal nitrate/PAN and metal acetylacetonate/PAN). The effect of precursor concentration on the morphologies was investigated. Single-phase, NCO with an average diameter of 100 nm, porous interconnected fibrous morphology was revealed by FESEM and FETEM analysis. The hierarchical nanostructured 1D-spinel NiCo2O4 materials showed a remarkable electrocatalytic activity towards oxygen reduction and evolution in an aqueous alkaline medium. The extraordinary bi-functional catalytic activity towards both ORR and OER was observed by the low over potential (0.84 V), which is better than that of noble metal catalysts [Pt/C (1.16 V), Ru/C (1.01 V) and Ir/C (0.92 V)], making them promising cathode materials for metal-air batteries. Furthermore, the rechargeable zinc-air battery with NCO-A1 as a bifunctional electrocatalyst displays high activity and stability during battery discharge, charge, and cycling processes.