A novel composite (FMC) to serve as a durable 3D-clam-shaped bifunctional cathode catalyst for both primary and rechargeable zinc-air batteries

The in-situ construction of oxygen vacancies-rich NiCo2S4@NiMoO4/Ni2P multilevel nanoarray for high-performance aqueous Zn-ion batteries

The development of active and durable cathode materials is the key to achieving high-performance water-based zinc-ion batteries. In this work, the NiCo2S4@NiMoO4/Ni2P nanoarray was employed by hydrothermal and subsequent phosphine...

Exploiting a High-Performance "Double-Carbon" Structure Co9S8/GN Bifunctional Catalysts for Rechargeable Zn-Air Batteries

Rational synthesis of bifunctional electrocatalysts with high performance and strong durability is highly demanded rechargeable metal-air battery. In this work, ZIF-derived Co₉S₈/C coated with conductive graphene nanosheet (Co₉S₈/GN) was synthesized by a simple solvothermal method and formed a stable double-carbon structure. As expected, the prepared Co₉S₈/GN catalyst exhibits a high catalytic activity (ΔE: 0.88 V) and long-term durability toward both oxygen reduction reaction and oxygen evolution reaction (ORR and OER), which is even superior to the Pt/C + Ir/C mixture (0.91 V). In addition, the Zn-air battery with the Co₉S₈/GN catalyst showed higher power density (186 mW cm^-2) and more stable charge-discharge cycling performances (2000 cycles) than the Pt/C + Ir/C (118 mW cm^-2). Based on these analysis results, the favorable catalytic performance of ORR/OER should be illustrated by the following reasons: (i) large specific surface area and unique mesoporous structure, providing abundant active sites; (ii) good conductivity, accelerating the electrons transfer; and (iii) the unique stable "double-carbon" structures (metal-S-C-C), preventing the agglomeration of metal sulfide, building new quick transfer pathway, and forming the strong electron coupling ability and synergistic effect.

Plasma-Assisted Surface Modification on the Electrode Interface for Flexible Fiber-Shaped Zn-Polyaniline Batteries

A novel flexible fiber-shaped zinc-polyaniline battery (FZPB) is proposed to enhance the electrochemical performance, mass loading, and stability of polyaniline cathodes. To this end, electron-cyclotron-resonance oxygen plasma-modified carbon fibers are employed. During plasma treatment, on the carbon-fiber surface, O₂⁺ plasma breaks the C-C, C-H, and C-N bonds to form C radicals, while the O₂ molecules are broken down to reactive oxygen species (O⁺, O²⁺, O₂⁺, and O₂²⁺). The C radicals and the reactive oxygen species are combined to homogeneously form oxygen functional groups, such as -OH, -COOH, and -C═O. The surface area and total pore volume of the treated carbon fibers increase as the plasma attacks. During electrodeposition, aniline interacts with the oxygen functional groups to form N-O and N-H bonds and π-π stacking, resulting in a homogeneous and high-loading polyaniline structure and improved adhesion between polyaniline and carbon fibers. In an FZPB, the cathode with plasma-treated carbon fibers and a polyaniline loading of 0.158 mg mg_CF^-1 (i.e., 2.36 mg cm_CF^-1) exhibits a capacity retention of 95.39% after 200 cycles at 100 mA g^-1 and a discharge capacity of 83.96 mA h g^-1 at such a high current density of 2000 mA g^-1, which are ∼1.67 and 1.24 times those of the pristine carbon-fiber-based one, respectively. Furthermore, the FZPB exhibits high flexibility with a capacity retention of 86.4% after bending to a radius of 2.5 mm for 100 cycles as a wearable energy device.

An efficient bifunctional electrocatalyst derived from layer-by-layer self-assembly of a three-dimensional porous Co-N-C@graphene

Three-dimensional (3D) porous carbon-based materials with tunable composition and microstructure are of great interest for the development of oxygen involved electrocatalytic reactions. Here, we report the synthesis of 3D porous carbon-based electrocatalyst by self-assembling Co-metal organic frameworks (MOF) building blocks on graphene via a layer-by-layer technique. Precise control of the structure and morphology is achieved by varying the MOF layer to tune the electrocatalytic properties. The as-produced electrocatalyst exhibits an excellent catalytic activity for the oxygen reduction reaction in 0.1 mol L^-1 KOH, showing a high onset potential of 0.963 V vs. reversible hydrogen electrode (RHE) and a low tafel slope of 54 mV dec^-1, compared to Pt/C (0.934 V and 52 mV dec^-1, respectively). Additionally, it shows a slightly lower potential vs. RHE (1.72 V) than RuO₂ (1.75 V) at 10 mA cm^-2 in an alkaline electrolyte. A rechargeable Zn-air battery based on the as-produced 3D porous catalyst demonstrates a high peak power density of 119 mW cm^-2 at a cell voltage of 0.578 V while retaining an excellent stability over 250 charge-discharge cycles.

A coordination polymer-derived Co3O4/Co-N@NMC composite material as a Zn-air battery cathode electrocatalyst and microwave absorber

Zn-air batteries, promising energy storage equipment with high energy density, light weight and a compact structure, are a perfect power source for electric vehicles. For a Zn-air battery, the activity of the air cathode electrocatalyst plays an important role in its performance. Here, employing a coordination polymer as a precursor, a composite material built from Co3O4 and Co-N active centres with nitrogen-doped mesoporous carbon as a matrix has been synthesized successfully. This composite material possesses outstanding activity and stability in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes. It possesses a small half-wave potential (ORR1/2 = 0.786 V) and low overpotential (OER10 = 1.575 V) for the ORR and OER, respectively. With this composite material as an air cathode electrocatalyst, a rechargeable Zn-air battery was assembled successfully. During the discharge process, the maximum power density of this Zn-air battery is 122 mW cm-2 at 0.76 V. The specific capacity of this battery is 505 mA h g-1 at 25 mA cm-2. The voltage gap between the charge and discharge processes is only 0.744 V at 10 mA cm-2 and 1.308 V at 100 mA cm-2. This rechargeable battery also shows promising stability after long-term charge-discharge experiments. Furthermore, the composite material also exhibits outstanding microwave adsorption properties. Its maximum reflection loss (RL) arrives at -13.9 dB with a thickness of only 1.0 mm. Thus, we find that coordination polymers are an ideal precursor for Zn-air battery cathode electrocatalysts and microwave absorbers.

Integrating carbonyl iron with sponge to enable lightweight and dual-frequency absorption

In this work, sponge impregnated with iron pentacarbonyl was utilized to obtain a novel composite in which the carbonyl iron (CI) was embedded in a graphitized carbon matrix (CI-C). The CI that results from the thermal pyrolysis of iron pentacarbonyl can homogeneously disperse into the pore structures of the sponge skeleton, which not only improves the stability of the CI, but also modifies the impedance matching character. Moreover, the sponge bulk turns into graphitized carbon during the heat treatment (graphitized catalysis of magnetic metal on carbon at high temperature). Due to the respective strong dissipation ability of CI and the graphitized carbon matrix, the as-prepared CI-C sample exhibits a good microwave absorption performance, including expanding the effective absorption bandwidth and reduced weight, compared to pure CI. Moreover, the sample with 30 wt% paraffin loading not only shows strong reflection loss absorbing ability, but also possesses continuous dual-absorption peaks (9.96 GHz, -38.7 dB, and 13.8 GHz is -37.6 dB). This work not only extends the application of carbonyl iron as a lightweight microwave absorber with dual-absorption peaks but also initiates a new approach for artificially designed carbon-based composites via a simple sponge-impregnation method.

N-doped defective carbon with trace Co for efficient rechargeable liquid electrolyte-/all-solid-state Zn-air batteries

Simple synthesis of multifunctional electrocatalysts with plentiful active sites from earth-abundant materials is especially fascinating. Here, N-doped defective carbon with trace Co (1.5 wt%) was prepared via a scalable one pot solid pyrolysis process. The sample exhibits efficient bifunctional OER/ORR activity in alkaline, mainly ascribed to the unique micro-mesoporous structure (1-3 nm), high population of graphitic-N doping (up to 49.0%), abundant defects and the encapsulated Co nanoparticles with graphitized carbon. The according rechargeable liquid Zn-air batteries showed excellent performance (maximum power density of 154.0 mW cm^-2; energy density of 773 Wh kg^-1 at 5 mA cm^-2 and charging-discharging cycling stability over 100 cycles). As a proof-of-concept, the flexible, rechargeable all-solid-state Zn-air batteries were constructed, and displayed a maximum power density as high as 45.9 mW cm^-2, among the top level of those reported previously.

Co3O4/MnO2/Hierarchically Porous Carbon as Superior Bifunctional Electrodes for Liquid and All-Solid-State Rechargeable Zinc-Air Batteries

The design of efficient, durable, and affordable catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is very indispensable in liquid-type and flexible all-solid-state zinc-air batteries. Herein, we present a high-performance bifunctional catalyst with cobalt and manganese oxides supported on porous carbon (Co₃O₄/MnO₂/PQ-7). The optimized Co₃O₄/MnO₂/PQ-7 exhibited a comparable ORR performance with commercial Pt/C and a more superior OER performance than all of the other prepared catalysts, including commercial Pt/C. When applied to practical aqueous (6.0 M KOH) zinc-air batteries, the Co₃O₄/MnO₂/porous carbon hybrid catalysts exhibited exceptional performance, such as a maximum discharge peak power density as high as 257 mW cm^-2 and the most stable charge-discharge durability over 50 h with negligible deactivation to date. More importantly, a series of flexible all-solid-state zinc-air batteries can be fabricated by the Co₃O₄/MnO₂/porous carbon with a layer-by-layer method. The optimal catalyst (Co₃O₄/MnO₂/PQ-7) exhibited an excellent peak power density of 45 mW cm^-2. The discharge potentials almost remained unchanged for 6 h at 5 mA cm^-2 and possessed a long cycle life (2.5 h@5 mA cm^-2). These results make the optimized Co₃O₄/MnO₂/PQ-7 a promising cathode candidate for both liquid-type and flexible all-solid-state zinc-air batteries.