Zn-air Battery Performance Research Articles

Redox‐Mediated Two‐Electron Oxygen Reduction Reaction with Ultrafast Kinetics for Zn–Air Flow Battery

AbstractRechargeable Zn–air batteries (ZABs) as high‐energy density and cost‐effective power sources for next generation energy storage have attracted considerable attention. However, the sluggish oxygen electrochemistry leads to high polarization of the air electrode during charge/discharge and consequently a low round‐trip energy efficiency of the cell. Here it is shown that the two‐electron oxygen redox chemistry enabled by a redox mediator, anthraquinone‐2,7‐disulfonic acid disodium salt (AQDS), can effectively boost the performance of ZABs. The kinetics and underlying mechanism of the AQDS‐mediated oxygen reduction reaction at different pH are scrutinized both computationally and experimentally to delineate the reaction pathways and rate‐limiting step. An ultrafast catalytic rate constant of 2.53 × 106 s–1 is achieved at a pH of 13.13 and based on a flow cell configuration, the AQDS‐mediated Zn–air flow battery demonstrates considerably enhanced energy efficiency of 85% at 10 mA cm−2.

Designing a nickel(ii) thiourea-formaldehyde polymer/nanocarbon bifunctional molecular catalyst with superior ORR, OER activities and its application to Zn–air battery

We report the design of a bifunctional molecular catalyst composed of a Ni-coordinated poly(thiourea-formaldehyde) polymer and a nanocarbon, that exhibits very high ORR, OER and Zn–air battery performance.

Heteroatom-doped carbon sheets as metal-free electrocatalysts for promoting the oxygen reduction reaction in Zn-air batteries.

Zn-air batteries are promising energy devices for future sustainable development. It is crucial to promote the cathodic reaction, oxygen reduction reaction (ORR), by applying active electrocatalysts. Herein, a metal-free ORR electrocatalyst has been fabricated by doping S and N atoms into carbon sheets (S-N-C), and it displays high ORR activity and outstanding performance in Zn-air batteries. The S-N-C electrocatalyst exhibits remarkable ORR activity with a half-wave potential of 0.89 V, which is far exceeding that of the commercial Pt/C benchmark and most reported carbon-based electrocatalysts. A full-cell Zn-air battery device with S-N-C as a cathode catalyst is demonstrated, which delivers high power density and good durability.

Probing the Co role in promoting the OER and Zn–air battery performance of NiFe-LDH: a combined experimental and theoretical study

We report a facile approach to construct Co@NiFe-LDH heterostructure catalyst with superior OER and Zn–air performance. DFT calculations revealed that Fe site is the OER active center, while forming heterostructure upshifts the Fe d-band center.

Understanding Electron Configurations and Coordination Environment for Enhanced Orr Process and Improved Zn-Air Battery Performance

Understanding Electron Configurations and Coordination Environment for Enhanced Orr Process and Improved Zn-Air Battery Performance

A Study on the Self-Discharge Behavior of Zinc-Air Batteries with CuO Additives

Zn-air batteries have promise as the next generation of batteries. However, their self-discharge behavior due to the hydrogen evolution reaction (HER) and corrosion of the Zn anode reduce their electrochemical performance. Copper (II) oxide (CuO) effectively suppresses the corrosion and HER. In addition, different electrochemical behavior can be obtained with different shape of nano CuO. To improve the performance of Zn-air batteries, in this study we synthesized nano CuO by the hydrothermal synthesis method with different volumes of NaOH solutions. Materials were characterized by XRD, FE-SEM, and EDX analysis. The sphere-like nano CuO (S-CuO) showed a specific discharge capacity of 428.8 mAh/g and 359.42 mAh/g after 1 h and 12 h storage, respectively. It also showed a capacity retention rate of 83.8%. In contrast, the other nano CuO additives showed a lower performance than pure Zn. The corrosion behavior of nano CuO additives was analyzed through Tafel extrapolation. S-CuO showed an Icorr of 0.053 A/cm2, the lowest value among the compared nano CuO materials. The results of our comparative study suggest that the sphere-like nano CuO additive is the most effective for suppressing the self-discharge of Zn-air batteries.

Boosting the ORR active and Zn-air battery performance through ameliorating the coordination environment of iron phthalocyanine

Iron phthalocyanine (FePc) with unique iron-pyrrolic nitrogen (Fe-N) structure has attracted an increasing attention on the oxygen reduction reaction (ORR). Unfortunately, the Fe-N site is not “active” because of its symmetry in the plane and always exhibits unsatisfactory ORR activity. Herein, we design a non-contact scheme of axial carbon substrate induced Fe-N electron localization to improve its ORR performance. Theoretical calculation indicates that the addition of MWCNTs causes the aggregation of electron cloud around Fe-N, enhances the oxygen adsorption capacity and accelerates the ORR rate. The obtained catalyst shows a Tafel slope of 35.8 mV·dec−1, an initial potential of 0.979 V vs. RHE, a half-wave potential of 0.902 V vs. RHE and a limiting current density of 5.42 mA·cm−2 in alkaline medium. The Zn-air battery assembled by this catalyst also demonstrates a large discharge voltage of 1.296 V, considerable power density of 102 mW·cm−2 and superior cycling stability (500 cycles). This work not only simplifies the process of preparing high efficiency transition metal catalysts but also does some tentative explore for realizing the practical use of Zn-air battery.

Enhanced bifunctional catalytic activities of N-doped graphene by Ni in a 3D trimodal nanoporous nanotubular network and its ultralong cycling performance in Zn-air batteries

Free-standing and flexible air electrodes with long-lasting bifunctional activities for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are crucial to the development of wearable Zn-air rechargeable batteries. In this work, we synthesize a flexible air electrode consisting of 3D nanoporous N-doped graphene with trimodal shells and Ni particles through repeated chemical vapor deposition (CVD) and acidic etching processes. Our results indicate that such trimodal graphene morphology significantly enhances the active N-dopant sites and graphene-coated Ni surface, which consequentially boosts both the ORR and OER activities, as well as catalytic durability. First-principles density functional theory (DFT) calculations reveal the synergetic effects between the Ni and the N-doped graphene; namely, the Ni nanoparticles boost the bifunctional activities of the coated N-doped graphene, and in turn the graphene-covering layers enhance the stability of Ni. Thanks to the better protection from the triple graphene shells, our trimodal N-doped graphene/Ni-based Zn-air battery can be stably discharged/recharged beyond 2500 h with low overpotentials. It is reasonable to expect that such free-standing trimodal graphene/Ni would be promising in many flexible energy conversion/storage devices.

Facile fabrication of N-doped graphene/ Ti3C2Tx (Mxene) aerogel with excellent electrocatalytic activity toward oxygen reduction reaction in fuel cells and metal-air batteries

High cost, limited sources and poor durability hinder the wide use of noble metal based catalysts especially platinum (Pt) based materials for the oxygen reduction reaction (ORR). The design and fabrication of efficient non-platinum based electrocatalysts which are cost-effective and durable are pivotal steps to advances of energy conversion devices such as fuel cells and batteries. In this study, we prepared 3D porous N-doped graphene hybrid structure with two dimensional ultralight Ti3C2Tx (Mxene) nanosheets through hydrothermal method and freez-drying. The Mxene nanosheets not only perform as 2D conductive platform for charge transfer but provide large specific surface area for reactant species to interact with catalyst. The abundance of N rich catalytic sites, high degree of carbon graphitization and appropriate surface area make Mxene, N-doped graphene aerogel (Mxene/NGA) as a favorable catalyst for ORR. It presents comparable catalytic activity (onset potential of 1.003 ​V vs RHE and current density (at 0.2 ​V vs RHE) of 5.65 ​mA ​cm2) with commercial 10% Pt/C (onset potential of 1.000 ​V vs RHE and current density (at 0.2 ​V) of 5.75 ​mA ​cm2). In addition, its durability over long operation time (40000s) is much better than that of Pt/. The Mxene/NGA also presents a noticeable Zn–air battery performance and its performance exceeds that of a 20 ​wt% Pt/C and IrO2 battery, rendering excellent chance for its utilization in green energy technologies.

V2C MXene synergistically coupling FeNi LDH nanosheets for boosting oxygen evolution reaction

Oxygen evolution reaction (OER) is a pivotal electrochemical reaction process for many renewable energy technologies. Due to the sluggish OER kinetics, searching for efficient low-cost non-precious metal catalysts is one of the crucial but very challenging steps. Herein, V2C MXene synergistically coupled with hypophosphite-intercalated FeNi (oxy)hydroxide (H2PO2−/FeNi-LDH-V2C) electrocatalyst is synthesized. The H2PO2−/FeNi-LDH-V2C exhibits excellent OER performance with an overpotential of 250 mV (η10) and small Tafel slope of 46.5 mV dec−1 in 1.0 M KOH electrolyte, and excellent rechargeable Zn-air battery performance with superior open circuit potential (1.42 eV), power density (137 mW cm−2) and well durability. The strong interaction and electronic coupling with prominent charge-transfer between FeNi-LDHs and V2C MXene endow the composite significant OER performance and structural stability, and the adsorption/desorption balance for the OER reaction pathway, eventually promoting the intrinsic activity. This work demonstrates the great promise of MXene-based nanohybrids as advanced electrocatalysts for renewable energy applications.

Synthesis of three‐dimensional Co/ CoO /N‐doped carbon nanotube composite for zinc air battery

Development of bifunctional electrocatalysts for oxygen electrocatalytic reactions is significant in improving the performance of Zn-air batteries. Among all candidates, transition metal compounds and carbon nanotube composites have attracted considerable attention owing to their great catalytic activities. Herein, three-dimensional (3D) macroporous carbon nanotube (CNT) microspheres interconnected with thorn-like N-doped CNT surrounding Co/CoO ([email protected]/CoO-bC) are synthesized via spray pyrolysis, followed by N-doped CNT growth and oxidation. Hierarchical nanohybrids with porous N-doped CNT-network and Co/CoO catalysts are rationally designed and applied as an efficient oxygen electrocatalyst. The porous carbon backbone exhibits high electrical conductivity with robust corrosion resistance. In addition, interconnected N-doped CNTs wrapping Co/CoO nanocatalysts exhibit enhanced catalytic properties as compared to commercial Pt/C and RuO2 in alkaline media. [email protected]/CoO-bC exhibits a robust cycle stability, higher power density, and lower polarization potential difference when applied as the oxygen electrode in a rechargeable Zn-air battery, in comparison to commercial Pt/C-RuO2 mixed powders.

N, F and S doped carbon nanofibers generated from electrospun polymerized ionic liquids for metal-free bifunctional oxygen electrocatalysis

• Electrospinning was used to prepare multiple heteroatom-doped metal-free nanofibrous material derived from PAN and polymerized ionic liquids • A simple method of producing a free-standing air cathode with high surface area and micro-mesoporous structures • Remarkably enhanced bifunctional electrocatalytic performance and durability of the electrocatalyst • DFT calculations confirm the N, S, F tri-doping can effectively promote the catalytic performance of carbon nanofibers • Highly efficient rechargeable Zn-air batteries without organic binder and supportive materials been successfully assembled The rational development of promising oxygen electrocatalysts with remarkable electrocatalytic activity, high stability and low cost is highly important for wide-scale application of sustainable energy technologies. Here, a novel free-standing metal-free carbon-based bifunctional electrocatalyst (NFS-CNF) with uniform multiple heteroatom (N, F and S) doping and large specific surface area (1450.7 m 2 g −1 ), was firstly synthesized by direct pyrolysis of electrospun polyacrylonitrile (PAN)/polymerized ionic liquid (PIL) nanofibers. The as-prepared NFS-CNF presents superior oxygen catalytic performance as well as excellent durability, exhibiting a positive half-wave potential (0.91 V) for oxygen reduction reaction (ORR) and a low overpotential (380 mV at 10 mA cm −2 ) for oxygen evolution reaction (OER) in alkaline medium. Notably, the outstanding bifunctional ORR/OER activity (ΔE=0.70 V) endows remarkable Zn-air battery performance with a peak power density of 127.5 mW cm −2 , a high specific capacity of 826.4 mAh g Zn −1 (corresponding to an energy density of ~991 Wh kg Zn −1 ), a stable cyclability after 600 cycles at 10 mA cm −2 with a voltage gap increase as small as 0.1 V. Density functional theory (DFT) calculations confirm that the N, F, S tri-doping contributes to the improvement in the electrochemical properties of our material. Our work firstly experimentally demonstrates a simple pathway of combining PIL precursor and electrospinning technology to achieve multiple heteroatom doping in metal-free nanofibrous bifunctional oxygen electrocatalysts with greatly enhanced electrochemical activity and durability. Additionally, the realization of efficient rechargeable Zn-air batteries suggests the promising future of our NFS-CNF pieces as robust free-standing air cathodes in various sustainable energy applications.

Tuning the electronic structure of nanoporous Ag via alloying effect from Cu to boost the ORR and Zn-air battery performance

The Ag-based materials are drawing successive attentions as cathode for oxygen reduction reaction (ORR) towards high performance metal-air batteries and polymer electrolyte membrane fuel cells. Its catalytic performance has been profoundly influenced by the active sites and mass transportation channels. Herein, nanoporous AgCu (NP-AgCu) catalysts are fabricated by tuning the Ag/Cu ratio to optimize its electronic structure. The XRD and XPS results demonstrate that the d-band center of Ag moves closer to the Fermi level owing to the alloying effect from Cu. Adopted as electrocatalyst, NP-Ag4Cu exhibits a 7-fold enhancement in oxygen reduction activity as compared to NP-Ag. Upon potential cycling and chronoamperometry, NP-Ag4Cu also presents better stability after 5000 cycles and 20000 s than Pt/C. The NP-Ag4Cu was also used as cathode for Zn-air battery and demonstrate a power density of 151.5 mW cm−2, which compares favorably to that of NP-Ag (83.8 mW cm−2) ascribed to the improved cathodic activity. The present study provides a facile way to boost the ORR performance of Ag-based electrocatalyst and promote its applications in Zn-air batteries.

The dual-nitrogen-source strategy to modulate a bifunctional hybrid Co/Co–N–C catalyst in the reversible air cathode for Zn-air batteries

The Zn-air battery is a promising next-generation battery because of the higher energy density and safety compared with the Li-ion battery. However, the Zn-air battery suffers from huge energy loss and poor cycling performance, which are due to the sluggish kinetics of oxygen reduction/evolution reactions (ORR/OER) and the instability of bifunctional catalysts. The state-of-the-art bifunctional catalyst is the composite of Pt and Ir/Ru oxides, which is hindered by the scarce resource and high cost. Therefore, developing low-cost and high-efficient bifunctional non-noble metal-based catalysts is essential to the deployment of Zn-air batteries. Herein, we report a dual-nitrogen-source mediated pyrolysis route to rationally design and synthesize the hybrid Co/Co–N–C bifunctional catalyst. The tailored catalyst consisting of carbon confined Co nanoparticles and atomically dispersed Co–N–C moiety is identified. Remarkably, the dual-nitrogen-source derived Co/Co–N–C catalyst demonstrates excellent electrochemical performances with a half-wave potential of 0.882 V for ORR and a potential of 1.640 V at 10 mA cm−2 for OER; reasonably, the bifunctionality of Co/Co–N–C, which is supported by the excellent self-breathing Zn-air battery performance (the maximum energy density of 897.1 Wh kgZn−1; no obvious degradation within 167h cycling). The abundant Co-Nx sites and metallic Co nanoparticles synergistically boost the ORR and OER.

Porous FeCo Glassy Alloy as Bifunctional Support for High‐Performance Zn‐Air Battery

AbstractThe Zn‐air battery (ZAB) is attracting increasing attention due to its high safety and preeminent performance. However, the practical application of ZAB relies heavily on developing durable support materials to replace conventional carbon supports which have unrecoverable corrosion issues, severely jeopardizing ZAB performance. Herein, a novel porous FeCo glassy alloy is developed as a bifunctional catalytic support for ZAB. The conducting skeleton of the porous glassy alloy is used to stabilize oxygen reduction cocatalysts, and more importantly, the FeCo serves as the primary phase for oxygen evolution. To demonstrate the concept of catalytic glassy alloy support, ultrasmall Pd nanoparticles are anchored, as oxygen reduction active sites, on the porous FeCo (noted as Pd/FeCo) for ZAB. The Pd/FeCo exhibits a significantly improved electrocatalytic activity for oxygen reduction (a half‐wave potential of 0.85 V) and oxygen evolution (a potential of 1.55 V to reach 10 mA cm−2) in the alkaline media. When used in the ZAB, the Pd/FeCo delivers an output power density of 117 mW cm−2 and outstanding cycling stability for over 200 h (400 cycles), surpassing the conventional carbon‐supported Pt/C+IrO2 catalysts. Such an integrated design that combines highly active components with a porous architecture provides a new strategy to develop novel nanostructured electrocatalysts.

Interfacing spinel NiCo2O4 and NiCo alloy derived N-doped carbon nanotubes for enhanced oxygen electrocatalysis

The active sites on oxygen electrocatalyst and the number of inherent active species are important factors affecting the performance of Zn-air battery. Constructing multiphase interfaces is an effective strategy to increase the number of active species for oxygen electrocatalysts. In this work, the number of intrinsic active species of spinel oxygen electrocatalyst was increased and its catalytic activity was enhanced by the synergistic action of bimetallic center three interfaces and heteroatom-doped carbon nanostructures. The resulting NiCo2O4/NCNTs/NiCo as catalyst exhibits superior activity toward ORR (E1/2 = 0.83 V, JL = −5.38 mA cm−2) and OER (Ej10 = 1.58 V). Further, the obtained catalyst work as a cathode assembles as Zn-air battery with a high open-circuit potential of 1.51 V and excellent cycle stability (586 h). Theoretical results indicate that the desorption of *OH species is the rate-determining step for ORR, the multiphase interfaces in the NiCo2O4/NCNTs/NiCo will provide additional electrons due to the upward shift of antibonding orbitals relative to the Fermi level. Consequently, it boosts the oxygen adsorption and charge transfer and accelerate the reaction kinetics. This work emphasizes the synergistic effect between multiphase interfaces in transition metal composite catalysts and opens up a promising way for the preparation of efficient and stable transition metal electrocatalysts.

3D-ordered macroporous N-doped carbon encapsulating Fe-N alloy derived from a single-source metal-organic framework for superior oxygen reduction reaction

Fe-N compounds with excellent electrocatalytic oxygen reduction activity are considered to be one of the most promising non-precious metal materials for fuel cells. Fe-N compounds with excellent electrocatalytic oxygen reduction activity are considered to be one of the most promising non-precious metal materials for fuel cells, which focuses on the Fe-N4 single-atom catalysts and the iron nitride materials (such as Fe2N and Fe3N). A hybridized catalyst having a hierarchical porous structure with regular macropores could enable the desired mass transfer efficiency in the catalytic process. In this study, we have constructed a new type of hybrid catalyst having iron and iron-nitrogen alloy nanoparticles (Fe-N austenite, termed as Fe-NA) embedded in the three-dimensional ordered macroporous N-doped carbon (3DOM Fe/Fe-NA@NC) by direct pyrolysis of single-source dicyandiamide-based iron metal-organic frameworks. The as-synthesized composites preserve the hierarchical porous carbon framework with ordered macropores and high specific surface area, incorporating the uniformly dispersed iron/iron-nitrogen austenite nanoparticles. Thereby, the striking architectural configuration embedded with highly active catalytic species delivers a superior oxygen reduction activity with a half-wave potential of 0.88 V and a subsequent superior Zn-air battery performance with high open-circuit voltage and continuous stability as compared to those using a commercial 20% Pt/C catalyst.

Molten salt assisted synthesis of three dimensional FeNx/N,S–C bifunctional catalyst for highly compressible, stretchable and rechargeable Zn-Air battery

All-solid-state rechargeable Zn-air battery is deemed to be a promising class of power source for its attractive operational safety and mechanical flexibility. To achieve high performance of Zn-air battery, the density of active sites on the ORR/OER bifunctional electrocatalyst and the maximized access to them are of great importance. In this study, a nitrogen, sulfur and ferric co-doped three-dimensional bifunctional catalyst (FeNx/N,S–C) is developed via a facile and eco-friendly molten salt assisted synthesis. The homogeneously dispersed FeNx species, the surrounding S dopants and the 3D hierarchical architecture synergistically endow FeNx/N,S–C with dense active sites with high accessibility, abundant open pores/channels and efficient mass transfer. Compared with the commercial Pt/C–RuO2 catalyst, the application of FeNx/N,S–C in all-solid-state rechargeable Zn-air batteries results in enhanced ORR/OER activities, lower charge-discharge voltage gaps and improved 52 h cycling durability, implying its good feasibility in practical application. The all-solid-state FeNx/N,S–C based battery shows no performance decay during charge-discharge cycles when its sodium polyacrylate hydrogel electrolyte is compressed up to 67% strain or stretched up to 400% length, implying the feasibility of the present FeNx/N,S–C catalyst in the usage of stable and flexible electronics.

Sulphur modulated Ni3FeN supported on N/S co-doped graphene boosts rechargeable/flexible Zn-air battery performance

Exploring feasible strategy for preparation of sulfur (S) modulated NiFe compounds and meanwhile clarifying the performance promoting mechanism of such catalysts has triggered numerous interest in rechargeable Zinc-air battery research field. Herein, S modulated Ni3FeN supported on N/S co-doped graphene (S-Ni3FeN/NSG) is synthesized via controlling the nitriding process of NiFe disulfides. The beneficial effect of the design strategy and S decoration on electrocatalytic activity are determined and analysed systematacially. The S-Ni3FeN/NSG-700 delivers excellent bifunctional oxygen electrocatalysis performance with half-wave potential of 0.878 V for ORR and low OER overpotential of 260 mV at 10 mA cm−2. Density Functional Theory (DFT) calculations demonstrate that S decoration effectively promotes the formation of OOH* intermediates and observably decreases the maximum of change of the Gibbs free energies for four primitive OER steps. Notably, when S-Ni3FeN/NSG-700 as air electrode applied in Zn-air battery test, the device shows superb durability for 1200 discharge/charge cycles at 10 mA cm-2. The corresponding all-solid Zinc-air battery exhibits excellent mechanical flexibility and a high power density of 140.1 mW cm-2. Two Zinc-air batteries in series can long-term stably power a self-made water-splitting device. This work provides new insights into highly efficient and low-cost bifunctional oxygen electrocatalyst designing.

Improving the Performance of Zn-Air Batteries with N-Doped Electroexfoliated Graphene.

The constantly growing demand for active, durable, and low-cost electrocatalysts usable in energy storage devices, such as supercapacitors or electrodes in metal-air batteries, has triggered the rapid development of heteroatom-doped carbon materials, which would, among other things, exhibit high catalytic activity in the oxygen reduction reaction (ORR). In this article, a method of synthesizing nitrogen-doped graphene is proposed. Few-layered graphene sheets (FL-graphene) were prepared by electrochemical exfoliation of commercial graphite in a Na2SO4 electrolyte with added calcium carbonate as a separator of newly-exfoliated FL-graphene sheets. Exfoliated FL-graphene was impregnated with a suspension of green algae used as a nitrogen carrier. Impregnated FL-graphene was carbonized at a high temperature under the flow of nitrogen. The N-doped FL-graphene was characterized through instrumental methods: high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Electrochemical performance was determined using cyclic voltamperometry and linear sweep voltamperometry to check catalytic activity in ORR. The N-doped electroexfoliated FL-graphene obeyed the four-electron transfer pathways, leading us to further test these materials as electrode components in rechargeable zinc-air batteries. The obtained results for Zn-air batteries are very important for future development of industry, because the proposed graphene electrode materials do not contain any heavy and noble metals in their composition.