Defect Engineering toward Atomic Co–Nx–C in Hierarchical Graphene for Rechargeable Flexible Solid Zn‐Air Batteries

Rechargeable flexible solid Zn‐air battery, with a high theoretical energy density of 1086 Wh kg^?1, is among the most attractive energy technologies for future flexible and wearable electronics; nevertheless, the practical application is greatly hindered by the sluggish oxygen reduction reaction/oxygen evolution reaction (ORR/OER) kinetics on the air electrode. Precious metal‐free functionalized carbon materials are widely demonstrated as the most promising candidates, while it still lacks effective synthetic methodology to controllably synthesize carbocatalysts with targeted active sites. This work demonstrates the direct utilization of the intrinsic structural defects in nanocarbon to generate atomically dispersed Co–N_x–C active sites via defect engineering. As‐fabricated Co/N/O tri‐doped graphene catalysts with highly active sites and hierarchical porous scaffolds exhibit superior ORR/OER bifunctional activities and impressive applications in rechargeable Zn‐air batteries. Specifically, when integrated into a rechargeable and flexible solid Zn‐air battery, a high open‐circuit voltage of 1.44 V, a stable discharge voltage of 1.19 V, and a high energy efficiency of 63% at 1.0 mA cm^?2 are achieved even under bending. The defect engineering strategy provides a new concept and effective methodology for the full utilization of nanocarbon materials with various structural features and further development of advanced energy materials.     

Bifunctional Transition Metal Hydroxysulfides: Room‐Temperature Sulfurization and Their Applications in Zn–Air Batteries

Bifunctional electrocatalysis for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) constitutes the bottleneck of various sustainable energy devices and systems like rechargeable metal–air batteries. Emerging catalyst materials are strongly requested toward superior electrocatalytic activities and practical applications. In this study, transition metal hydroxysulfides are presented as bifunctional OER/ORR electrocatalysts for Zn–air batteries. By simply immersing Co‐based hydroxide precursor into solution with high‐concentration S^2?, transition metal hydroxides convert to hydroxysulfides with excellent morphology preservation at room temperature. The as‐obtained Co‐based metal hydroxysulfides are with high intrinsic reactivity and electrical conductivity. The electron structure of the active sites is adjusted by anion modulation. The potential for 10 mA cm^?2 OER current density is 1.588 V versus reversible hydrogen electrode (RHE), and the ORR half‐wave potential is 0.721 V versus RHE, with a potential gap of 0.867 V for bifunctional oxygen electrocatalysis. The Co₃FeS_1.5(OH)₆ hydroxysulfides are employed in the air electrode for a rechargeable Zn–air battery with a small overpotential of 0.86 V at 20.0 mA cm^?2, a high specific capacity of 898 mAh g^?1, and a long cycling life, which is much better than Pt and Ir‐based electrocatalyst in Zn–air batteries.     

Interfacing Manganese Oxide and Cobalt in Porous Graphitic Carbon Polyhedrons Boosts Oxygen Electrocatalysis for Zn–Air Batteries

Rational design and synthesis of highly active and robust bifunctional non‐noble electrocatalysts for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are urgently required for efficient rechargeable metal–air batteries. Herein, abundant MnO/Co heterointerfaces are engineered in porous graphitic carbon (MnO/Co/PGC) polyhedrons via a facile hydrothermal‐calcination route with a bimetal–organic framework as the precursor. The in situ generated Co nanocrystals not only create well‐defined heterointerfaces with high conductivity to overcome the poor OER activity but also promote the formation of robust graphitic carbon. Owing to the desired composition and formation of the heterostructures, the resulting MnO/Co/PGC exhibits superior activity and stability toward both OER and ORR, which makes it an efficient air cathode for the rechargeable Zn–air battery. Importantly, the homemade Zn–air battery is able to deliver excellent performance including a peak power density of 172 mW cm^?2 and a specific capacity of 872 mAh g^?1, as well as excellent cycling stability (350 cycles), outperforming commercial mixed Pt/C||RuO₂ catalysts. This work highlights the synergy from heterointerfaces in oxygen electrocatalysis, thus providing a promising approach for advanced metal–air cathode materials.     

Boosting Bifunctional Oxygen Electrocatalysis with 3D Graphene Aerogel‐Supported Ni/MnO Particles

Electrocatalysts for oxygen‐reduction and oxygen‐evolution reactions (ORR and OER) are crucial for metal–air batteries, where more costly Pt‐ and Ir/Ru‐based materials are the benchmark catalysts for ORR and OER, respectively. Herein, for the first time Ni is combined with MnO species, and a 3D porous graphene aerogel‐supported Ni/MnO (Ni–MnO/rGO aerogel) bifunctional catalyst is prepared via a facile and scalable hydrogel route. The synthetic strategy depends on the formation of a graphene oxide (GO) crosslinked poly(vinyl alcohol) hydrogel that allows for the efficient capture of highly active Ni/MnO particles after pyrolysis. Remarkably, the resulting Ni–MnO/rGO aerogels exhibit superior bifunctional catalytic performance for both ORR and OER in an alkaline electrolyte, which can compete with the previously reported bifunctional electrocatalysts. The MnO mainly contributes to the high activity for the ORR, while metallic Ni is responsible for the excellent OER activity. Moreover, such bifunctional catalyst can endow the homemade Zn–air battery with better power density, specific capacity, and cycling stability than mixed Pt/C + RuO₂ catalysts, demonstrating its potential feasibility in practical application of rechargeable metal–air batteries.     

Ni‐Fe Nitride Nanoplates on Nitrogen‐Doped Graphene as a Synergistic Catalyst for Reversible Oxygen Evolution Reaction and Rechargeable Zn‐Air Battery

Obtaining bifunctional electrocatalysts with high activity for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is a main hurdle in the application of rechargeable metal‐air batteries. Earth‐abundant 3d transition metal‐based catalysts have been developed for the OER and ORR; however, most of these are based on oxides, whose insulating nature strongly restricts their catalytic performance. This study describes a metallic Ni‐Fe nitride/nitrogen‐doped graphene hybrid in which 2D Ni‐Fe nitride nanoplates are strongly coupled with the graphene support. Electronic structure of the Ni‐Fe nitride is changed by hybridizing with the nitrogen‐doped graphene. The unique heterostructure of this hybrid catalyst results in very high OER activity with the lowest onset overpotential (150 mV) reported, and good ORR activity comparable to that for commercial Pt/C. The high activity and durability of this bifunctional catalyst are also confirmed in rechargeable zinc‐air batteries that are stable for 180 cycles with an overall overpotential of only 0.77 V at 10 mA^?2.     

Co Nanoislands Rooted on Co–N–C Nanosheets as Efficient Oxygen Electrocatalyst for Zn–Air Batteries

Developing non‐precious‐metal bifunctional oxygen reduction and evolution reaction (ORR/OER) catalysts is a major task for promoting the reaction efficiency of Zn–air batteries. Co‐based catalysts have been regarded as promising ORR and OER catalysts owing to the multivalence characteristic of cobalt element. Herein, the synthesis of Co nanoislands rooted on Co–N–C nanosheets supported by carbon felts (Co/Co–N–C) is reported. Co nanosheets rooted on the carbon felt derived from electrodeposition are applied as the self‐template and cobalt source. The synergistic effect of metal Co islands with OER activity and Co–N–C nanosheets with superior ORR performance leads to good bifuctional catalytic performances. Wavelet transform extended X‐ray absorption fine spectroscopy and X‐ray photoelectron spectroscopy certify the formation of Co (mainly Co⁰) and the Co–N–C (mainly Co²⁺ and Co³⁺) structure. As the air‐cathode, the assembled aqueous Zn–air battery exhibits a small charge–discharge voltage gap (0.82 V@10 mA cm^?2) and high power density of 132 mW cm^?2, outperforming the commercial Pt/C catalyst. Additionally, the cable flexible rechargeable Zn–air battery exhibits excellent bendable and durability. Density functional theory calculation is combined with operando X‐ray absorption spectroscopy to further elucidate the active sites of oxygen reactions at the Co/Co–N–C cathode in Zn–air battery.     

Single Fe Atom on Hierarchically Porous S,N‐Codoped Nanocarbon Derived from Porphyra Enable Boosted Oxygen Catalysis for Rechargeable Zn‐Air Batteries

Iron–nitrogen–carbon materials (Fe–N–C) are known for their excellent oxygen reduction reaction (ORR) performance. Unfortunately, they generally show a laggard oxygen evolution reaction (OER) activity, which results in a lethargic charging performance in rechargeable Zn–air batteries. Here porous S‐doped Fe–N–C nanosheets are innovatively synthesized utilizing a scalable FeCl₃‐encapsulated‐porphyra precursor pyrolysis strategy. The obtained electrocatalyst exhibits ultrahigh ORR activity (E_1/2 = 0.84 V vs reversible hydrogen electrode) and impressive OER performance (E_{j = 10} = 1.64 V). The potential gap (ΔE = E_{j = 10} ? E_1/2) is 0.80 V, outperforming that of most highly active bifunctional electrocatalysts reported to date. Furthermore, the key role of S involved in the atomically dispersed Fe–Nx species on the enhanced ORR and OER activities is expounded for the first time by ultrasound‐assisted extraction of the exclusive S source (taurine) from porphyra. Moreover, the assembled rechargeable Zn–air battery comprising this bifunctional electrocatalyst exhibits higher power density (225.1 mW cm^?2) and lower charging–discharging overpotential (1.00 V, 100 mA cm^?2 compared to Pt/C + RuO₂ catalyst). The design strategy can expand the utilization of earth‐abundant biomaterial‐derived catalysts, and the mechanism investigations of S doping on the structure–activity relationship can inspire the progress of other functional electrocatalysts.     

Reduced Graphene Oxide‐Wrapped Co9–xFexS8/Co,Fe‐N‐C Composite as Bifunctional Electrocatalyst for Oxygen Reduction and Evolution

Searching for highly efficient bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) using nonnoble metal‐based catalysts is essential for the development of many energy conversion systems, including rechargeable fuel cells and metal–air batteries. Here, Co_9–xFe_xS₈/Co,Fe‐N‐C hybrids wrapped by reduced graphene oxide (rGO) (abbreviated as S‐Co_9–xFe_xS₈@rGO) are synthesized through a semivulcanization and calcination method using graphene oxide (GO) wrapped bimetallic zeolite imidazolate framework (ZIF) Co,Fe‐ZIF (CoFe‐ZIF@GO) as precursors. Benefiting from the synergistic effect of OER active CoFeS and ORR active Co,Fe‐N‐C in a single component, as well as high dispersity and enhanced conductivity derived from rGO coating and Fe‐doping, the obtained S‐Co_9–xFe_xS₈@rGO‐10 catalyst shows an ultrasmall overpotential of ≈0.29 V at 10 mA cm^?2 in OER and a half‐wave potential of 0.84 V in ORR, combining a superior oxygen electrode activity of ≈0.68 V in 0.1 m KOH.     

Hollow Co3O4 Nanosphere Embedded in Carbon Arrays for Stable and Flexible Solid‐State Zinc–Air Batteries

Highly active and durable air cathodes to catalyze both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are urgently required for rechargeable metal–air batteries. In this work, an efficient bifunctional oxygen catalyst comprising hollow Co₃O₄ nanospheres embedded in nitrogen‐doped carbon nanowall arrays on flexible carbon cloth (NC‐Co₃O₄/CC) is reported. The hierarchical structure is facilely derived from a metal–organic framework precursor. A carbon onion coating constrains the Kirkendall effect to promote the conversion of the Co nanoparticles into irregular hollow oxide nanospheres with a fine scale nanograin structure, which enables promising catalytic properties toward both OER and ORR. The integrated NC‐Co₃O₄/CC can be used as an additive‐free air cathode for flexible all‐solid‐state zinc–air batteries, which present high open circuit potential (1.44 V), high capacity (387.2 mAh g^?1, based on the total mass of Zn and catalysts), excellent cycling stability and mechanical flexibility, significantly outperforming Pt‐ and Ir‐based zinc–air batteries.     

Co Nanoparticles Confined in 3D Nitrogen‐Doped Porous Carbon Foams as Bifunctional Electrocatalysts for Long‐Life Rechargeable Zn–Air Batteries

Proper design and simple preparation of nonnoble bifunctional electrocatalysts with high cost performance and strong durability for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is highly demanded but still full of enormous challenges. In this work, a spontaneous gas‐foaming strategy is presented to synthesize cobalt nanoparticles confined in 3D nitrogen‐doped porous carbon foams (CoNCF) by simply carbonizing the mixture of citric acid, NH₄Cl, and Co(NO₃)₂·6H₂O. Thanks to its particular 3D porous foam architecture, ultrahigh specific surface area (1641 m² g^?1), and homogeneous distribution of active sites (C–N, Co–N_x, and Co–O moieties), the optimized CoNCF‐1000‐80 (carbonized at 1000 °C, containing 80 mg Co(NO₃)₂·6H₂O in precursors) catalyst exhibits a remarkable bifunctional activity and long‐term durability toward both ORR and OER. Its bifunctional activity parameter (ΔE) is as low as 0.84 V, which is much smaller than that of noble metal catalyst and comparable to state‐of‐the‐art bifunctional catalysts. When worked as an air electrode catalyst in rechargeable Zn–air batteries, a high energy density (797 Wh kg^?1), a low charge/discharge voltage gap (0.75 V), and a long‐term cycle stability (over 166 h) are achieved at 10 mA cm^?2.     

Novel MOF‐Derived Co@N‐C Bifunctional Catalysts for Highly Efficient Zn–Air Batteries and Water Splitting

Metal–organic frameworks (MOFs) and MOF‐derived materials have recently attracted considerable interest as alternatives to noble‐metal electrocatalysts. Herein, the rational design and synthesis of a new class of Co@N‐C materials (C‐MOF‐C2‐T) from a pair of enantiotopic chiral 3D MOFs by pyrolysis at temperature T is reported. The newly developed C‐MOF‐C2‐900 with a unique 3D hierarchical rodlike structure, consisting of homogeneously distributed cobalt nanoparticles encapsulated by partially graphitized N‐doped carbon rings along the rod length, exhibits higher electrocatalytic activities for oxygen reduction and oxygen evolution reactions (ORR and OER) than that of commercial Pt/C and RuO₂, respectively. Primary Zn–air batteries based on C‐MOF‐900 for the oxygen reduction reaction (ORR) operated at a discharge potential of 1.30 V with a specific capacity of 741 mA h g_Zn^–1 under 10 mA cm^–2. Rechargeable Zn–air batteries based on C‐MOF‐C2‐900 as an ORR and OER bifunctional catalyst exhibit initial charge and discharge potentials at 1.81 and 1.28 V (2 mA cm^–2), along with an excellent cycling stability with no increase in polarization even after 120 h – outperform their counterparts based on noble‐metal‐based air electrodes. The resultant rechargeable Zn–air batteries are used to efficiently power electrochemical water‐splitting systems, demonstrating promising potential as integrated green energy systems for practical applications.     

“Wiring” Fe‐Nx‐Embedded Porous Carbon Framework onto 1D Nanotubes for Efficient Oxygen Reduction Reaction in Alkaline and Acidic Media

This study presents a novel metal‐organic‐framework‐engaged synthesis route based on porous tellurium nanotubes as a sacrificial template for hierarchically porous 1D carbon nanotubes. Furthermore, an ultrathin Fe‐ion‐containing polydopamine layer has been introduced to generate highly effective FeN_xC active sites into the carbon framework and to induce a high degree of graphitization. The synergistic effects between the hierarchically porous 1D carbon structure and the embedded FeN_xC active sites in the carbon framework manifest in superior catalytic activity toward oxygen reduction reaction (ORR) compared to Pt/C catalyst in both alkaline and acidic media. A rechargeable zinc‐air battery assembled in a decoupled configuration with the nonprecious pCNT@Fe@GL/CNF ORR electrode and Ni‐Fe LDH/NiF oxygen evolution reaction (OER) electrode exhibits charge–discharge overpotentials similar to the counterparts of Pt/C ORR electrode and IrO₂ OER electrode.     

Metal and Nonmetal Codoped 3D Nanoporous Graphene for Efficient Bifunctional Electrocatalysis and Rechargeable Zn–Air Batteries

Developing bifunctional electrocatalysts with high activities and long durability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial toward the practical implementation of rechargeable metal–air batteries. Here, a 3D nanoporous graphene (np‐graphene) doped with both N and Ni single atoms/clusters is reported. The predoping of N by chemical vapor deposition (CVD) dramatically increases the Ni doping amount and stability. The resulting N and Ni codoped np‐graphene has excellent electrocatalytic activities for both the ORR and the OER in alkaline aqueous solutions. The synergetic effects of N and Ni dopants are revealed by density functional theory calculations. The free‐standing Ni,N codoped 3D np‐graphene shows great potential as an economical catalyst/electrode for metal–air batteries.     

Metal–Organic‐Framework‐Derived Hybrid Carbon Nanocages as a Bifunctional Electrocatalyst for Oxygen Reduction and Evolution

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are cornerstone reactions for many renewable energy technologies. Developing cheap yet durable substitutes of precious‐metal catalysts, especially the bifunctional electrocatalysts with high activity for both ORR and OER reactions and their streamlined coupling process, are highly desirable to reduce the processing cost and complexity of renewable energy systems. Here, a facile strategy is reported for synthesizing double‐shelled hybrid nanocages with outer shells of Co‐N‐doped graphitic carbon (Co‐NGC) and inner shells of N‐doped microporous carbon (NC) by templating against core–shell metal–organic frameworks. The double‐shelled NC@Co‐NGC nanocages well integrate the high activity of Co‐NGC shells into the robust NC hollow framework with enhanced diffusion kinetics, exhibiting superior electrocatalytic properties to Pt and RuO₂ as a bifunctional electrocatalyst for ORR and OER, and hold a promise as efficient air electrode catalysts in Zn–air batteries. First‐principles calculations reveal that the high catalytic activities of Co‐NGC shells are due to the synergistic electron transfer and redistribution between the Co nanoparticles, the graphitic carbon, and the doped N species. Strong yet favorable adsorption of an OOH* intermediate on the high density of uncoordinated hollow‐site C atoms with respect to the Co lattice in the Co‐NGC structure is a vital rate‐determining step to achieve excellent bifunctional electrocatalytic activity.     

Defect Engineering of Chalcogen‐Tailored Oxygen Electrocatalysts for Rechargeable Quasi‐Solid‐State Zinc–Air Batteries

A critical bottleneck limiting the performance of rechargeable zinc–air batteries lies in the inefficient bifunctional electrocatalysts for the oxygen reduction and evolution reactions at the air electrodes. Hybridizing transition‐metal oxides with functional graphene materials has shown great advantages due to their catalytic synergism. However, both the mediocre catalytic activity of metal oxides and the restricted 2D mass/charge transfer of graphene render these hybrid catalysts inefficient. Here, an effective strategy combining anion substitution, defect engineering, and the dopant effect to address the above two critical issues is shown. This strategy is demonstrated on a hybrid catalyst consisting of sulfur‐deficient cobalt oxysulfide single crystals and nitrogen‐doped graphene nanomeshes (CoO_0.87S_0.13/GN). The defect chemistries of both oxygen‐vacancy‐rich, nonstoichiometric cobalt oxysulfides and edge‐nitrogen‐rich graphene nanomeshes lead to a remarkable improvement in electrocatalytic performance, where CoO_0.87S_0.13/GN exhibits strongly comparable catalytic activity to and much better stability than the best‐known benchmark noble‐metal catalysts. In application to quasi‐solid‐state zinc–air batteries, CoO_0.87S_0.13/GN as a freestanding catalyst assembly benefits from both structural integrity and enhanced charge transfer to achieve efficient and very stable cycling operation over 300 cycles with a low discharge–charge voltage gap of 0.77 V at 20 mA cm^?2 under ambient conditions.     

Nitrogen,Fluorine, and Boron Ternary Doped Carbon Fibers as Cathode Electrocatalysts for Zinc–Air Batteries

Zinc–air batteries with high‐density energy are promising energy storage devices for the next generation of energy storage technologies. However, the battery performance is highly dependent on the efficiency of oxygen electrocatalyst in the air electrode. Herein, the N, F, and B ternary doped carbon fibers (TD‐CFs) are prepared and exhibited higher catalytic properties via the efficient 4e⁻ transfer mechanism for oxygen reduction in comparison with the single nitrogen doped CFs. More importantly, the primary and rechargeable Zn–air batteries using TD‐CFs as air–cathode catalysts are constructed. When compared to batteries with Pt/C + RuO₂ and Vulcan XC‐72 carbon black catalysts, the TD‐CFs catalyzed batteries exhibit remarkable battery reversibility and stability over long charging/discharging cycles.     

Oxygen Vacancy–Rich In‐Doped CoO/CoP Heterostructure as an Effective Air Cathode for Rechargeable Zn–Air Batteries

An efficient and low‐cost electrocatalyst for reversible oxygen electrocatalysis is crucial for improving the performance of rechargeable metal?air batteries. Herein, a novel oxygen vacancy–rich 2D porous In‐doped CoO/CoP heterostructure (In‐CoO/CoP FNS) is designed and developed by a facile free radicals–induced strategy as an effective bifunctional electrocatalyst for rechargeable Zn–air batteries. The electron spin resonance and X‐ray absorption near edge spectroscopy provide clear evidence that abundant oxygen vacancies are formed in the interface of In‐CoO/CoP FNS. Owing to abundant oxygen vacancies, porous heterostructure, and multiple components, In‐CoO/CoP FNS exhibits excellent oxygen reduction reaction activity with a positive half‐wave potential of 0.81 V and superior oxygen evolution reaction activity with a low overpotential of 365 mV at 10 mA cm^?2. Moreover, a home‐made Zn–air battery with In‐CoO/CoP FNS as an air cathode delivers a large power density of 139.4 mW cm^?2, a high energy density of 938 Wh kg_Zn^?1, and can be steadily cycled over 130 h at 10 mA cm^?2, demonstrating great application potential in rechargeable metal–air batteries.     

Simultaneously Integrating Single Atomic Cobalt Sites and Co9S8 Nanoparticles into Hollow Carbon Nanotubes as Trifunctional Electrocatalysts for Zn–Air Batteries to Drive Water Splitting

The development of rechargeable metal–air batteries and water electrolyzers are highly constrained by electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). However, the construction of efficient trifunctional electrocatalysts for ORR/OER/HER are highly desirable yet challenging. Herein, hollow carbon nanotubes integrated single cobalt atoms with Co₉S₈ nanoparticles (CoSA + Co₉S₈/HCNT) are fabricated by a straightforward in situ self‐sacrificing strategy. The structure of the CoSA + Co₉S₈/HCNT are verified by X‐ray absorption spectroscopy and aberration‐corrected scanning transmission electron microscopy. Theoretical calculations and experimental results embrace the synergistic effects between Co₉S₈ nanoparticles and single cobalt atoms through optimizing the electronic configuration of the CoN₄ active sites to lower the reaction barrier and facilitating the ORR, OER, and HER simultaneously. Consequently, rechargeable liquid and all‐solid‐state flexible Zn–air batteries based on CoSA + Co₉S₈/HCNT exhibit remarkable stability and excellent power density of 177.33 and 51.85 mW cm^?2, respectively, better than Pt/C + RuO₂ counterparts. Moreover, the as‐fabricated Zn–air batteries can drive an overall water splitting device assembled with CoSA + Co₉S₈/HCNT and achieve a current density of 10 mA cm^?2 at a low voltage of 1.59 V, also superior to Pt/C + RuO₂. Therefore, this work presents a promising approach to an efficient trifunctional electrocatalyst toward practical applications.     

Controllable Construction of Core–Shell Polymer@Zeolitic Imidazolate Frameworks Fiber Derived Heteroatom‐Doped Carbon Nanofiber Network for Efficient Oxygen Electrocatalysis

Designing rational nanostructures of metal–organic frameworks based carbon materials to promote the bifunctional catalytic activity of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is highly desired but still remains a great challenge. Herein, an in situ growth method to achieve 1D structure‐controllable zeolitic imidazolate frameworks (ZIFs)/polyacrylonitrile (PAN) core/shell fiber (PAN@ZIFs) is developed. Subsequent pyrolysis of this precursor can obtain a heteroatom‐doped carbon nanofiber network as an efficient bifunctional oxygen electrocatalyst. The electrocatalytic performance of derived carbon nanofiber is dominated by the structures of PAN@ZIFs fiber, which is facilely regulated by efficiently controlling the nucleation and growth process of ZIFs on the surface of polymer fiber as well as optimizing the components of ZIFs. Benefiting from the core–shell structures with appropriate dopants and porosity, as‐prepared catalysts show brilliant bifunctional ORR/OER catalytic activity and durability. Finally, the rechargeable Zn‐air battery assembled from the optimized catalyst (CNF@Zn/CoNC) displays a peak power density of 140.1 mW cm^?2, energy density of 878.9 Wh kg_Zn^?1, and excellent cyclic stability over 150 h, giving a promising performance in realistic application.     

Graphene-Encapsulated Bifunctional Catalysts with High Activity and Durability for Zn–Air Battery

Carbon-based electrocatalysts with both high activity and high stability are desirable for use in Zn–air batteries. However, the carbon corrosion reaction (CCR) is a critical obstacle in rechargeable Zn–air batteries. In this study, a cost-effective carbon-based novel material is reported with a high catalytic effect and good durability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), prepared via a simple graphitization process. In situ growth of graphene is utilized in a 3D-metal-coordinated hydrogel by introducing a catalytic lattice of transition metal alloys. Due to the direct growth of few-layer graphene on the metal alloy decorated 3d-carbon network, greatly reduced CCR is observed in a repetitive OER test. As a result, an efficient bifunctional electrocatalytic performance is achieved with a low ΔE value of 0.63 V and good electrochemical durability for 83 h at a current density of 10 mA cm⁻² in an alkaline media. Moreover, graphene-encapsulated transition metal alloys on the nitrogen-doped carbon supporter exhibit an excellent catalytic effect and good durability in a Zn–air battery system. This study suggests a straightforward way to overcome the CCR of carbon-based materials for an electrochemical catalyst with wide application in energy conversion and energy storage devices.