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1.
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–Nx–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.  相似文献   

2.
Oxidizing vacancies in nitrogen‐doped carbon have recently been reported to enhance the oxygen reaction activity of air cathodes, but their specific role has remained elusive and controversial. Herein, the critical role of oxidizing the vacancies in enhancing the oxygen reduction reaction for metal–air battery is identified with density functional theory. Deliberate introduction of oxygen‐enriched vacancies in nitrogen‐doped carbon is shown experimentally to provide superior oxygen reduction activity. In situ X‐ray powder diffraction gives direct observation of the oxygen reactions in a zinc–air battery catalyzed by vacancy‐enriched oxidized carbon; the intensity changes of the carbon peak show continuous chemisorption of oxygen intermediates on the carbon cathode during discharge. The air‐cathode performance is shown to exceed that with Pt/C+IrO2 catalysts.  相似文献   

3.
The lithium–air (Li–O2) battery has been deemed one of the most promising next‐generation energy‐storage devices due to its ultrahigh energy density. However, in conventional porous carbon–air cathodes, the oxygen gas and electrolyte often compete for transport pathways, which limit battery performance. Here, a novel textile‐based air cathode is developed with a triple‐phase structure to improve overall battery performance. The hierarchical structure of the conductive textile network leads to decoupled pathways for oxygen gas and electrolyte: oxygen flows through the woven mesh while the electrolyte diffuses along the textile fibers. Due to noncompetitive transport, the textile‐based Li–O2 cathode exhibits a high discharge capacity of 8.6 mAh cm?2, a low overpotential of 1.15 V, and stable operation exceeding 50 cycles. The textile‐based structure can be applied to a range of applications (fuel cells, water splitting, and redox flow batteries) that involve multiple phase reactions. The reported decoupled transport pathway design also spurs potential toward flexible/wearable Li–O2 batteries.  相似文献   

4.
Under development for next‐generation wearable electronics are flexible, knittable, and wearable energy‐storage devices with high energy density that can be integrated into textiles. Herein, knittable fiber‐shaped zinc–air batteries with high volumetric energy density (36.1 mWh cm?3) are fabricated via a facile and continuous method with low‐cost materials. Furthermore, a high‐yield method is developed to prepare the key component of the fiber‐shaped zinc–air battery, i.e., a bifunctional catalyst composed of atomically thin layer‐by‐layer mesoporous Co3O4/nitrogen‐doped reduced graphene oxide (N‐rGO) nanosheets. Benefiting from the high surface area, mesoporous structure, and strong synergetic effect between the Co3O4 and N‐rGO nanosheets, the bifunctional catalyst exhibits high activity and superior durability for oxygen reduction and evolution reactions. Compared to a fiber‐shaped zinc–air battery using state‐of‐the‐art Pt/C + RuO2 catalysts, the battery based on these Co3O4/N‐rGO nanosheets demonstrates enhanced and stable electrochemical performance, even under severe deformation. Such batteries, for the first time, can be successfully knitted into clothes without short circuits under external forces and can power various electronic devices and even charge a cellphone.  相似文献   

5.
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 gZn–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.  相似文献   

6.
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 kgZn?1, and can be steadily cycled over 130 h at 10 mA cm?2, demonstrating great application potential in rechargeable metal–air batteries.  相似文献   

7.
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 S2?, 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 Co3FeS1.5(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.  相似文献   

8.
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 (CoO0.87S0.13/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 CoO0.87S0.13/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, CoO0.87S0.13/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.  相似文献   

9.
Driven by the intensified demand for energy storage systems with high‐power density and safety, all‐solid‐state zinc–air batteries have drawn extensive attention. However, the electrocatalyst active sites and the underlying mechanisms occurring in zinc–air batteries remain confusing due to the lack of in situ analytical techniques. In this work, the in situ observations, including X‐ray diffraction and Raman spectroscopy, of a heteroatom‐doped carbon air cathode are reported, in which the chemisorption of oxygen molecules and oxygen‐containing intermediates on the carbon material can be facilitated by the electron deficiency caused by heteroatom doping, thus improving the oxygen reaction activity for zinc–air batteries. As expected, solid‐state zinc–air batteries equipped with such air cathodes exhibit superior reversibility and durability. This work thus provides a profound understanding of the reaction principles of heteroatom‐doped carbon materials in zinc–air batteries.  相似文献   

10.
The oxygen reduction reaction (ORR) is a core reaction for electrochemical energy technologies such as fuel cells and metal–air batteries. ORR catalysts have been limited to platinum, which meets the requirements of high activity and durability. Over the last few decades, a variety of materials have been tested as non‐Pt catalysts, from metal–organic complex molecules to metal‐free catalysts. In particular, nitrogen‐doped graphitic carbon materials, including N‐doped graphene and N‐doped carbon nanotubes, have been extensively studied. However, due to the lack of understanding of the reaction mechanism and conflicting knowledge of the catalytic active sites, carbon‐based catalysts are still under the development stage of achieving a performance similar to Pt‐based catalysts. In addition to the catalytic viewpoint, designing mass transport pathways is required for O2. Recently, the importance of pyridinic N for the creation of active sites for ORR and the requirement of hydrophobicity near the active sites have been reported. Based on the increased knowledge in controlling ORR performances, bottom‐up preparation of N‐doped carbon catalysts, using N‐containing conjugative molecules as the assemblies of the catalysts, is promising. Here, the recent understanding of the active sites and the mechanism of ORRs on N‐doped carbon catalysts are reviewed.  相似文献   

11.
Developing efficient and low‐cost defective carbon‐based catalysts for the oxygen reduction reaction (ORR) is essential to metal–air batteries and fuel cells. Active sites engineering toward these catalysts is highly desirable but challenging to realize boosted catalytic performance. Herein, a sandwich‐like confinement route to achieve the controllable regulation of active sites for carbon‐based catalysts is reported. In particular, three distinct catalysts including metal‐free N‐doped carbon (NC), single Co atoms dispersed NC (Co–N–C), and Co nanoparticles‐contained Co–N–C (Co/Co–N–C) are controllably realized and clearly identified by synchrotron radiation‐based X‐ray spectroscopy. Electrochemical measurements suggest that the Co/Co–N–C catalyst delivers optimized ORR performance due to the rich Co–Nx active sites and their synergistic effect with metallic Co nanoparticles. This work provides deep insight for rationally designing efficient ORR catalyst based on active sites engineering.  相似文献   

12.
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–Nx, 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.  相似文献   

13.
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.  相似文献   

14.
The highly oxidative operating conditions of rechargeable zinc–air batteries causes significant carbon‐support corrosion of bifunctional oxygen electrocatalysts. Here, a new strategy for the catalyst support design focusing on oxygen vacancy (OV)‐rich, low‐bandgap semiconductor is proposed. The OVs promote the electrical conductivity of the oxide support, and at the same time offer a strong metal–support interaction (SMSI), which enables the catalysts to have small metal size, high catalytic activity, and high stability. The strategy is demonstrated by successfully synthesizing ultrafine Co‐metal‐decorated 3D ordered macroporous titanium oxynitride (3DOM‐Co@TiOxNy). The 3DOM‐Co@TiOxNy catalyst exhibits comparable activities for oxygen reduction and evolution reactions, but much higher cycling stability than noble metals in alkaline conditions. The zinc–air battery using this catalyst delivers an excellent stability with less than 1% energy efficiency loss over 900 charge–discharge cycles at 20 mA cm?2. The high stability is attributed to the strong SMSI between Co and 3DOM‐TiOxNy which is verified by density functional theory calculations. This work sheds light on using OV‐rich semiconductors as a promising support to design efficient and durable nonprecious electrocatalysts.  相似文献   

15.
The nonaqueous lithium oxygen battery is a promising candidate as a next‐generation energy storage system because of its potentially high energy density (up to 2–3 kW kg?1), exceeding that of any other existing energy storage system for storing sustainable and clean energy to reduce greenhouse gas emissions and the consumption of nonrenewable fossil fuels. To achieve high energy density, long cycling stability, and low cost, the air electrode structure and the electrocatalysts play important roles. Here, a metal‐free, free‐standing macroporous graphene@graphitic carbon nitride (g‐C3N4) composite air cathode is first reported, in which the g‐C3N4 nanosheets can act as efficient electrocatalysts, and the macroporous graphene nanosheets can provide space for Li2O2 to deposit and also promote the electron transfer. The electrochemical results on the graphene@g‐C3N4 composite air electrode show a 0.48 V lower charging plateau and a 0.13 V higher discharging plateau than those of pure graphene air electrode, with a discharge capacity of nearly 17300 mA h g?1 (composite). Excellent cycling performance, with terminal voltage higher than 2.4 V after 105 cycles at 1000 mA h g?1 (composite) capacity, can also be achieved. Therefore, this hybrid material is a promising candidate for use as a high energy, long‐cycle‐life, and low‐cost cathode material for lithium oxygen batteries.  相似文献   

16.
The oxygen reduction reaction (ORR) plays an important role in the fields of energy storage and conversion technologies, including metal–air batteries and fuel cells. The development of nonprecious metal electrocatalysts with both high ORR activity and durability to replace the currently used costly Pt‐based catalyst is critical and still a major challenge. Herein, a facile and scalable method is reported to prepare ZIF‐8 with single ferrocene molecules trapped within its cavities (Fc@ZIF‐8), which is utilized as precursor to porous single‐atom Fe embedded nitrogen‐doped carbon (Fe–N–C) during high temperature pyrolysis. The catalyst shows a half‐wave potential (E1/2) of 0.904 V, 67 mV higher than commercial Pt/C catalyst (0.837 V), which is among the best compared with reported results for ORR. Significant electrochemical properties are attributed to the special configuration of Fc@ZIF‐8 transforming into a highly dispersed iron–nitrogen coordination moieties embedded carbon matrix.  相似文献   

17.
With the extensive research and development of renewable energy technologies, there is an increasing interest in developing metal‐free carbons as a new class of bifunctional electrocatalysts for boosting the performance of metal–air batteries. Along with significant understanding of the electrocatalytic nature and the rapid development of techniques, the activities of carbon electrocatalysts are well‐tailored by introducing particular dopants/defects and structure regulation. Herein, the recent advances regarding the rational design of carbon‐based electrocatalysts for the oxygen reduction reaction and oxygen evolution reaction are summarized, with a special focus on the bifunctional applications in Zn–air and Li–air batteries. Specifically, the atomic modulation strategies to regulate the electrocatalytic activities of carbons and structure modification are summarized to gain deep insights into bifunctional mechanisms and boost advanced Zn–air and Li–air batteries. The current challenges and future perspectives are also addressed to accelerate the exploration of promising bifunctional carbon catalysts for renewable energy technologies, particularly metal–air batteries.  相似文献   

18.
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.  相似文献   

19.
Synergistic improvements in the electrical conductivity and catalytic activity for the oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) are of paramount importance for rechargeable metal–air batteries. In this study, one‐nanometer‐scale ultrathin cobalt oxide (CoOx) layers are fabricated on a conducting substrate (i.e., a metallic Co/N‐doped graphene substrate) to achieve superior bifunctional activity in both the ORR and OER and ultrahigh output power for flexible Zn–air batteries. Specifically, at the atomic scale, the ultrathin CoOx layers effectively accelerate electron conduction and provide abundant active sites. X‐ray absorption spectroscopy reveals that the metallic Co/N‐doped graphene substrate contributes to electron transfer toward the ultrathin CoOx layer, which is beneficial for the electrocatalytic process. The as‐obtained electrocatalyst exhibits ultrahigh electrochemical activity with a positive half‐wave potential of 0.896 V for ORR and a low overpotential of 370 mV at 10 mA cm?2 for OER. The flexible Zn–air battery built with this catalyst exhibits an ultrahigh specific power of 300 W gcat ?1, which is essential for portable devices. This work provides a new design pathway for electrocatalysts for high‐performance rechargeable metal–air battery systems.  相似文献   

20.
Metal‐free electrocatalysts have been extensively developed to replace noble metal Pt and RuO2 catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in fuel cells or metal–air batteries. These electrocatalysts are usually deposited on a 3D conductive support (e.g., carbon paper or carbon cloth (CC)) to facilitate mass and electron transport. For practical applications, it is desirable to create in situ catalysts on the carbon fiber support to simplify the fabrication process for catalytic electrodes. In this study, the first example of in situ exfoliated, edge‐rich, oxygen‐functionalized graphene on the surface of carbon fibers using Ar plasma treatment is successfully prepared. Compared to pristine CC, the plasma‐etched carbon cloth (P‐CC) has a higher specific surface area and an increased number of active sites for OER and ORR. P‐CC also displays good intrinsic electron conductivity and excellent mass transport. Theoretical studies show that P‐CC has a low overpotential that is comparable to Pt‐based catalysts, as a result of both defects and oxygen doping. This study provides a simple and effective approach for producing highly active in situ catalysts on a carbon support for OER and ORR.  相似文献   

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