Catalytic Activity For Oxygen Reduction Research Articles

Revealing Isolated M−N3C1 Active Sites for Efficient Collaborative Oxygen Reduction Catalysis

AbstractSingle atom catalysts (SACs) are of great importance for oxygen reduction, a critical process in renewable energy technologies. The catalytic performance of SACs largely depends on the structure of their active sites, but explorations of highly active structures for SAC active sites are still limited. Herein, we demonstrate a combined experimental and theoretical study of oxygen reduction catalysis on SACs, which incorporate M−N3C1 site structure, composed of atomically dispersed transition metals (e.g., Fe, Co, and Cu) in nitrogenated carbon nanosheets. The resulting SACs with M−N3C1 sites exhibited prominent oxygen reduction catalytic activities in both acidic and alkaline media, following the trend Fe−N3C1 > Co−N3C1 > Cu−N3C1. Theoretical calculations suggest the C atoms in these structures behave as collaborative adsorption sites to M atoms, thanks to interactions between the d/p orbitals of the M/C atoms in the M−N3C1 sites, enabling dual site oxygen reduction.

Revealing Isolated M-N3 C1 Active Sites for Efficient Collaborative Oxygen Reduction Catalysis.

Single atom catalysts (SACs) are of great importance for oxygen reduction, a critical process in renewable energy technologies. The catalytic performance of SACs largely depends on the structure of their active sites, but explorations of highly active structures for SAC active sites are still limited. Herein, we demonstrate a combined experimental and theoretical study of oxygen reduction catalysis on SACs, which incorporate M-N3 C1 site structure, composed of atomically dispersed transition metals (e.g., Fe, Co, and Cu) in nitrogenated carbon nanosheets. The resulting SACs with M-N3 C1 sites exhibited prominent oxygen reduction catalytic activities in both acidic and alkaline media, following the trend Fe-N3 C1 > Co-N3 C1 > Cu-N3 C1 . Theoretical calculations suggest the C atoms in these structures behave as collaborative adsorption sites to M atoms, thanks to interactions between the d/p orbitals of the M/C atoms in the M-N3 C1 sites, enabling dual site oxygen reduction.

Nonprecious Bimetallic Sites Coordinated on N-Doped Carbons with Efficient and Durable Catalytic Activity for Oxygen Reduction.

Developing efficient, inexpensive, and durable electrocatalysts for the oxygen reduction reaction (ORR) is important for the large-scale commercialization of fuel cells and metal-air batteries. Herein, a hierarchically porous bimetallic Fe/Co single-atom-coordinated N-doped carbon (Fe/Co-Nx -C) electrocatalyst for ORR is synthesized from Fe/Co-coordinated polyporphyrin using silica template-assisted and silica-protection synthetic strategies. In the synthesis, first silica nanoparticles-embedded, silica-protected Fe/Co-polyporphyrin is prepared. It is then pyrolyzed and treated with acidic solution. The resulting Fe/Co-Nx -C material has a large specific surface area, large electrochemically active surface area, good conductivity, and catalytically active Fe/Co-Nx sites. The material exhibits a very good electrocatalytic activity for the ORR in alkaline media, with a half-wave potential of 0.86 V versus reversible hydrogen electrode, which is better than that of Pt/C (20 wt%). Furthermore, it shows an outstanding operational stability and durability during the reaction. A zinc-air battery (ZAB) assembled using Fe/Co-Nx -C as an air-cathode electrocatalyst gives a high peak power density (152.0 mW cm-2 ) and shows a good recovery property. Furthermore, the performance of the battery is better than a corresponding ZAB containing Pt/C as an electrocatalyst. The work also demonstrates a synthetic route to a highly active, stable, and scalable single-atom electrocatalyst for ORR in ZABs.

Ex‐Solved Ag Nanocatalysts: Ex‐Solved Ag Nanocatalysts on a Sr‐Free Parent Scaffold Authorize a Highly Efficient Route of Oxygen Reduction (Adv. Funct. Mater. 27/2020)

In article number 2001326, WooChul Jung and co-workers utilize a Ag ex-solution as the central strategy to demonstrate impressive oxygen reduction catalytic activity on BaCoO3−δ perovskites. The effective tactics incorporated in this study establish a milestone for the road toward exceptional performance outcomes from fuel cell cathodes in the low-to-intermediate temperature regimens given the use of the parent scaffold-offspring metal catalyst as a key skeleton feature.

Stable zigzag edges of transition-metal dichalcogenides with high catalytic activity for oxygen reduction

Developing non-precious and efficient oxygen reduction reaction (ORR) catalysts to replace Pt-based materials is of vital importance for hydrogen fuel cells. Transition-metal dichalcogenides (TMD) are a typical group of catalysts that have been previously applied for hydrogen-evolution and hydrodesulfurization reactions. Using density-functional-theory calculations, we explore the prospect of both traditional and Janus TMDs as electrochemical ORR catalysts by studying their planar surfaces and different kinds of edges. Among the tens of surfaces, armchair edges, and zigzag edges of Mo- and W-based systems screened here, we find that both excellent stability and high catalytic activity can be simultaneously achieved for the zigzag edges of WSe2 and WSSe. The overpotentials of different zigzag edges of WSe2 and WSSe vary between 0.43 and 0.64 V, as low as that of the prototypical Pt electrode (∼0.45 V). The comprehensive ORR activities of TMD-based surfaces and edges studied here, as well as the high ORR activity discovered for specific zigzag edges, can not only be readily validated by experiments but also facilitate their future related applications by providing a complete structure–property relationship. Those low overpotentials are benefited from the moderate OH–edge bonding strength, and the revealed microscopic electornic-structure mechanisms here will also be useful for further optimizing the ORR activities of TMD edges through, e.g., chemical, mechanical, and potentiostatic approaches.

N, S-codoped graphene supports for Ag-MnFe2O4 nanoparticles with improved performance for oxygen reduction and oxygen evolution reactions

Heterogeneous nanoparticles with synergistic effects between different composites are potential catalysts with bifunctional catalytic activity for oxygen reduction (ORR) and oxygen evolution reaction (OER). Herein, heteroatoms such as N and S are doped into graphene substrates to improve catalytic activity and structural stability of Ag-MnFe2O4 nanoparticles. Interestingly, these particles keep a primarily heterogeneous structure for their assembly on N, S-codoped graphene (NSG), while Ag domains shrink on S-doped graphene (SG) or N-doped graphene (NG). Subsequently, Ag-MnFe2O4/NSG shows the best bifunctional catalytic activity due to the improved stability of Ag-MnFe2O4 NPs on NSG and enhanced bonding energy between supports and particles. The Koutecky-Levich plots confirm a major four-electron reaction pathway for the ORRs on Ag-MnFe2O4/NSG. Meanwhile, Ag-MnFe2O4/NSG exhibits higher stability and better methanol tolerance than commercial Pt/C. Therefore, Ag-MnFe2O4/NSG with bi-functional catalytic activity for ORR and OER is a promising non-Pt catalyst candidate.

Boosting Oxygen Reduction of Single Iron Active Sites via Geometric and Electronic Engineering: Nitrogen and Phosphorus Dual Coordination.

Atomically dispersed transition metal active sites have emerged as one of the most important fields of study because they display promising performance in catalysis and have the potential to serve as ideal models for fundamental understanding. However, both the preparation and determination of such active sites remain a challenge. The structural engineering of carbon- and nitrogen-coordinated metal sites (M-N-C, M = Fe, Co, Ni, Mn, Cu, etc.) via employing new heteroatoms, e.g., P and S, remains challenging. In this study, carbon nanosheets embedded with nitrogen and phosphorus dual-coordinated iron active sites (denoted as Fe-N/P-C) were developed and determined using cutting edge techniques. Both experimental and theoretical results suggested that the N and P dual-coordinated iron sites were favorable for oxygen intermediate adsorption/desorption, resulting in accelerated reaction kinetics and promising catalytic oxygen reduction activity. This work not only provides efficient way to prepare well-defined single-atom active sites to boost catalytic performance but also paves the way to identify the dual-coordinated single metal atom sites.

Highly ordered macroporous dual-element-doped carbon from metal-organic frameworks for catalyzing oxygen reduction.

Multiple heteroatom-doped carbons with 3D ordered macro/meso-microporous structures have not been realized by simple carbonization of metal–organic frameworks (MOFs). Herein, ordered macroporous phosphorus- and nitrogen-doped carbon (M-PNC) is prepared successfully by carbonization of double-solvent-induced MOF/polystyrene sphere (PS) precursors accompanied with spontaneous removal of the PS template, followed by post-doping. M-PNC shows a high specific surface area of 837 m2 g−1, nitrogen doping of 3.17 at%, and phosphorus doping of 1.12 at%. Thanks to the hierarchical structure, high specific surface area, and multiple heteroatom-doping, M-PNC exhibits unusual catalytic activity as an electrocatalyst for the oxygen reduction reaction. Computational calculation reveals that the P Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O group helps stabilize the adsorption of intermediates, and the position of PO relative to graphitic N significantly improves the activity of the adjacent carbons for electrocatalysis.

The Proportion of Fe-NX , N Doping Species and Fe3 C to Oxygen Catalytic Activity in Core-Shell Fe-N/C Electrocatalyst.

A bifunctional oxygen electrocatalyst composed of iron carbide (Fe3 C) nanoparticles encapsulated by nitrogen doped carbon sheets is reported. X-ray photoelectron spectroscopy and X-ray absorption near edge structure revealed the presence of several kinds of active sites (Fe-Nx sites, N doping sites) and the modulated electron structure of nitrogen doped carbon sheets. Fe3 C@N-CSs shows excellent oxygen evolution and oxygen reduction catalytic activity owing to the modulated electron structure by encapsulated Fe3 C core via biphasic interfaces electron interaction, which can lower the free energy of intermediate, strengthen the bonding strength and enhance conductivity. Meanwhile, the contribution of the Fe-Nx sites, N doping sites and the effect of Fe3 C core for the electrocatalytic oxygen reaction is originally revealed. The Fe3 C@N-CSs air electrode-based zinc-air battery demonstrates a high open circuit potential of 1.47 V, superior charge-discharge performance and long lifetime, which outperforms the noble metal-based zinc-air battery.

Molecular Control of Heterogeneous Electrocatalysis through Graphite Conjugation.

The efficient interconversion of electrical and chemical energy requires catalysts capable of accelerating multielectron reactions at or near electrified interfaces. These reactions can be performed at metallic surface sites on heterogeneous electrocatalysts or through redox mediation at molecular electrocatalysts. The relative ease of synthesis and characterization for homogeneous catalysts has allowed for molecular-level control over the active site and permitted systematic tuning of activity and selectivity. Similar control is difficult to achieve with heterogeneous electrocatalysts, because they typically exhibit a distribution of active site geometries and local electronic structures, which are challenging to modify with molecular precision. However, metallic heterogeneous electrocatalysts benefit from a continuum of electronic states that distribute the redox burden of multielectron transformations, enabling more efficient catalysis. We envisioned that we could combine the attractive properties of molecular and heterogeneous catalysts by integrating tunable molecular active sites into the delocalized band states of a conductive solid. The Surendranath group has developed a class of electrocatalysts in which molecules are strongly electronically coupled to graphitic electrodes through a conductive, aromatic pyrazine linkage such that they behave like metallic surface active sites. In this Account, we discuss the dual role of these graphite-conjugated catalysts (GCCs) as a platform with which to answer molecular-level questions of metallic active sites and as a tool with which to fundamentally alter the mechanism and enhance the performance of molecular active sites. We begin by describing the electrochemical and spectroscopic studies that demonstrated that GCC sites behave like metallic active sites rather than simply as redox mediators attached to electrode surfaces. We then discuss how electrochemical studies of a series of graphite-conjugated acids enabled the construction of a molecular model for the thermochemistry of proton-coupled electron transfer reactions at GCC sites based on the pKa of the molecular analogue of the conjugated site and the potential of zero free charge of the electrode. In the final section, we discuss the effects of graphite conjugation on the mechanism and rate of oxygen reduction, hydrogen evolution, and carbon dioxide reduction catalysis across four different GCC platforms involving N-heterocycle, organometallic, and metalloporphyrin active sites. We discuss how molecular-level tuning at graphite-conjugated active sites directly correlates to changes in catalytic activity for the oxygen reduction reaction. We demonstrate that graphite-conjugated porphyrins show enhanced catalytic oxygen reduction activity over amide-linked porphyrins. Lastly, we describe how catalysis at graphite-conjugated sites proceeds through mechanisms involving concerted electron transfer and substrate activation, in stark contrast to the mechanisms observed for molecular analogues. Overall, we showcase how GCCs provide a rich platform for controlling heterogeneous catalysis at the molecular level.

Commercial-Level Energy Storage via Free-Standing Stacking Electrodes

Summary Pseudocapacitors with a fast faradic redox reaction during the electrochemical charge/discharge process hold great promise for delivering high power and high energy. Here, we used emerging oxygenated carbon nitride (OCN) as a model for nitrogen- and oxygen-enriched carbons and found an anion-selective charging behavior in aqueous electrolytes. The N- and O-mediated hydroxyl anion-selective charging originates from inbuilt surface-positive electrostatic potential localized at heptazine and quaternary N atom structural units. The carbon atoms in heptazine adjacent to pyridinic N act as the electron transfer active sites for faradic pseudocapacitance. The OCN free-standing films (FSFs) were developed as current collector-free electrodes, and stacking OCN FSFs can confer a cell with loading weight over a commercial level. For demonstration, a symmetrical cell with 17.7 mg cm−2 delivers an energy of 140.9 mW h at a high power of 2,499.9 mW, and almost 100% capacitance retention after 20,000 charge/discharge cycles at 50 mA.

Effect of Ag Addition on the Structural Properties of Ba0.5Sr0.5Co0.8Fe0.2O3-δ–Sm0.2Ce0.8O1.9 Composite Cathode Powder

Barium strontium cobalt ferrite (BSCF) materials are effective cathode materials for solid-oxide fuel cells (SOFCs) because of their high conductivity and excellent catalytic activity for oxygen reduction and mobility. The ionic conductivity of this type of composite cathode can be improved by adding some catalyst materials to help enhance their electrode activity toward oxygen reduction reaction. A catalyst material speeds up the reaction of the composite cathode and thus increases the oxygen-exchange rate and ionic-diffusion rate. This study aimed to investigate the effects of adding Ag as a catalyst material to Ba0.5Sr0.5Co0.8Fe0.2O3-δ–Sm0.2Ce0.8O1.9 (BSCF-SDC) composite cathode powders. The powders were mixed by high-energy ball milling at 550 rpm. After mixing and calcining at 950 °C for 2 hours, Ag was dry milled with the calcined BSCF-SDC composite cathode powder at five different weight percentages (1wt%–5wt%). The powders were characterized by various analytical methods. X-ray diffraction (XRD) was used for phase and structure identification. A Zetasizer Nano ZS was used to determine particle size. The Archimedes principle and field-emission scanning electron microscopy (FESEM) were used to examine density porosity and morphology, respectively. XRD results demonstrated that the BSCF-SDC-Ag peak increased with increased Ag amount. Zetasizer results revealed that the powder particles expanded in size, consistent with the FESEM images. Furthermore, the porosity ranged within sufficient values (20%–40%) needed for SOFC cathodes. All these findings indicated the effectiveness of the BSCF-SDC powders as SOFC cathode materials.

Effects of Crystallographic Structures of Metal-Phthalocyanine on Electrocatalytic Properties of Oxygen Reduction in Acidic Condition

Effects of the crystallographic structures of metal-phthalocyanines (metal: Co, Ni, Cu, Zn) between α and β phases on electrochemical oxygen reduction catalytic activities were investigated in acidic condition. As the distances of centered-metal in the structures of α and β phases are 3.8 A and 4.8 A, respectively, they were closed to the size of an oxygen molecule (3.6 A). The phases of metal-phthalocyanines were conducted by an interface deposition method. The obtained catalyst powders were characterized by means of X-ray diffraction and X-ray photoelectron spectra analyses. Electrochemical oxygen reduction performances were mainly measured by using a gas diffusion type carbon electrode loaded with a metal-phthalocyanine. It was confirmed that the catalytic activities of cobalt- and copper-centered phthalocyanines were enhanced by the conversion from β to α phases. The effects of the distance between the metals in the crystallographic structures of metal-phthalocyanines should be explained by the adsorbed oxygen states that depend on the distance between the metals. The α phase has the distance which allows to form the bridge configuration of oxygen molecule which requires two adsorption sites and that eventually produces H2O by the direct 4-electron pathway. Analysis with the rotating disk electrode system showed that the α-phased metal-phthalocyanines enhance the 4-electron reduction pathway.

Functionalization of 2D materials for enhancing OER/ORR catalytic activity in Li\u2013oxygen batteries

A major barrier toward the practical application of lithium-oxygen batteries is the high overpotential caused by the precipitation of oxygen-reduction products at the cathode, resulting in poor cyclability. By combining first-principle calculations and reactive molecular dynamics simulations, we show that surface functionalization of 2D MXene nanosheets offers a high degree of tunability of the catalytic activity for oxygen-reduction and oxygen-evolution reactions (ORR/OER). We show that the controlled creation of active vacancy sites on the MXene surface enhances ORR in excess of a factor of 60 compared to graphene-based cathode materials. Furthermore, we find that increasing the ratio of fluorine vs. oxygen termination of the functionalized Ti4N3-MXene catalyst reduces the charge overpotential by up to 70% and 80% compared with commercial platinum-on-carbon and graphene catalysts, respectively. These results provide direct guidance toward the rational design of functionalized 2D materials for modulating the catalytic activity for a wide range of electrocatalytic applications.

Warped graphitic layers generated by oxidation of fullerene extraction residue and its oxygen reduction catalytic activity

Carbon-based oxygen reduction reaction (ORR) catalysts are regarded as a promising candidate to replace the currently used Pt catalyst in polymer electrolyte fuel cells (PEFCs); however, the active sites remain under discussion. We predicted that warped graphitic layers (WGLs) are responsible for the ORR catalytic activity in some carbon catalysts (i.e., carbon alloy catalysts (CACs)). To prove our assumption, we needed to use WGLs consisting of carbon materials, but without any extrinsic catalytic elements, such as nitrogen, iron, or cobalt, which effectively enhance ORR activity. The present study employed a fullerene extraction residue as a starting material to construct WGLs. The oxidation of the material at 600 °C exposed the WGLs by removing the surrounding amorphous moieties. Transmission electron microscopy (TEM) observations revealed the formation of WGLs by oxidation treatment at 600 °C in an O2/N2 stream. Extending the oxidation time increased the purity of the WGL phase, but also simultaneously increased the concentration of oxygen-containing surface functional groups as monitored by temperature programmed desorption (TPD). The specific ORR activity increased with oxidation up to 1 h and then decreased with the intensive oxidation treatment. Correlations between the specific ORR activity and other parameters confirmed that the development of the WGL and the increase in the O/C ratio are the competing factors determining specific ORR activity. These results explain the maximum specific ORR activity after 1 h of oxidation time. WGLs were found to lower the heat of adsorption for O2 and to increase the occurrence of heterogeneous electron transfer.

Tailoring Electronic Structure of Atomically Dispersed Metal–N3S1 Active Sites for Highly Efficient Oxygen Reduction Catalysis

Rational design of oxygen electrocatalysts with high catalytic activity and long-term durability is currently a severe challenge for rechargeable Zn–air batteries. Here, we highlighted an electronic structure engineering on Cu-based catalyst with atomically dispersed Cu–N3S1 active sites, representing as highly active electrode material for oxygen reduction. The structurally-new Cu–N3S1 species shows unique electron interactions with both phosphorus atoms/carbon support, which not only activate the electron transfer around the Cu–N3S1 sites but also enhance the interaction with oxygenated species, resulting in a promoting reaction kinetics process. As expected, this catalyst exhibits superior catalytic activity for oxygen reduction and evolution. A rechargeable flexible solid Zn–air battery based on this catalyst behaves superior performance of a high open-circuit voltage (1.41 V), a large power density (138.2 mW/cm2), and a small charge/discharge voltage gap (0.72 V at 2.0 mA cm–2) even under different bending angles. Specifically, this strategy is general and can be extended to other metal single atom catalyst systems (such as Fe–N3S1 species). This work will open a new avenue to design structurally-new single atom catalysts for energy-related field.

Preparation of MnO2-Cr2O3 mesoporous oxide and its application for an active and reversible air catalyst for Li-O2 batteries

Preparation of highly porous MnO2 and Cr2O3 with regular structure was investigated in this study by using hard template method. Cr2O3 nanoarchitects with regular pore structure and α-MnO2 with porous nanosheet were successfully prepared. By mixing with single wall carbon nanotube (SWCNT), application of MnO2, Cr2O3 nano architects (Mn-Cr oxides supported SWCNT) was studied as active air electrode for Li-O2 battery which is now expecting as a new rechargeable battery with large capacity. It was found that the synergy effects between two mesoporous metal oxides with SWCNT resulted in excellent electrochemical properties of air electrode. Prepared Mn-Cr oxide supported SWCNT can sustain stable charge and discharge capacity up to 150 cycles with 500 mAh/g without capacity degradation indicating outstanding catalytic activity for oxygen reduction and evolution reaction (ORR/OER). Consecutive cyclic voltammetry tests also showed excellent reversibility of formation and decomposition of reaction products of Li2O2. This could be resulted from large pore volume and ordered structure of Cr2O3, MnO2/SWCNT air electrode.

Ni- and P-doped carbon from waste biomass: A sustainable multifunctional electrode for oxygen reduction, oxygen evolution and hydrogen evolution reactions

High performance electrocatalysts based on nickel nanoparticles and biomass derived carbon were fabricated via a sustainable, inexpensive synthetic route utilizing waste carrot as a naturally occurring carbon precursor containing abundant amounts of phosphorus and oxygen. The electrocatalytic performance of the fabricated electrodes with variable nickel mass loadings (0 ̶ 30 wt%) was investigated. For Ni mass loading of 19.3 wt%, the resulting Ni/P-doped carbon exhibits optimum catalytic activity for oxygen reduction (ORR), oxygen evolution (OER) and hydrogen evolution reaction (HER). The electrocatalyst reveals onset and half-wave potentials of 0.81 and 0.67 V vs. reversible hydrogen electrode (RHE), and a kinetic limiting current density of 13.66 mA cm−2 at 0.1 V vs. RHE for ORR. The material exhibits modest Tafel slopes of 67.6 and 134.9 mV dec−1 and overpotentials of 368 and 297 mV to reach a current density of 10 mA cm−2 for OER and HER, respectively. The results on the composite physicochemical characteristics, electrochemically active surface area, ionic conductivity and ionic diffusivity reveal a sustainable process to fabricate eco-friendly, trifunctional electrocatalysts having high efficiency.

Self-Supported ZIF-Derived Co3 O4 Nanoparticles-Decorated Porous N-Doped Carbon Fibers as Oxygen Reduction Catalyst.

Oxygen reduction is a significant cathodic reaction in the state-of-art clean energy devices such as fuel cell and metal-oxygen battery. Here, ZIF-incorporated hybrid polymeric fibres have been fabricated by using a dual-phase electrospinning method. These are then transformed into Co3 O4 -nanoparticle-decorated porous N-doped carbon fibres (ZIF-Co3 O4 /NCF) through multi-step annealing treatment. The resultant ZIF-Co3 O4 /NCF is interweaved into a self-supported film and can be used as a bi-functional catalyst for catalysing oxygen reduction in both aqueous and non-aqueous electrolytes. Electrochemical tests demonstrate that ZIF-Co3 O4 /NCF displays a high catalytic activity for oxygen reduction with a half-wave potential (E1/2 ) of 0.813 V (vs. RHE) and an almost favourable four-electron reduction pathway in alkaline medium. ZIF-Co3 O4 /NCF catalyst only shows 4 mV negative shift of E1/2 after 5000 continuous CV cycles. In addition, the ZIF-Co3 O4 /NCF can be applied as the cathode catalyst of non-aqueous Li-O2 battery, exhibiting a remarkable ORR activity in LiPF6 contained 1,2-dimethoxyethane electrolyte. The excellent electrocatalytic performance of ZIF-Co3 O4 /NCF is probably due to the abundance of active sites of graphitic carbon-wrapped Co3 O4 nanoparticles, as well as the cross-linked fibrous nitrogen-doped carbon texture.

In-situ embedding zeolitic imidazolate framework derived Co–N–C bifunctional catalysts in carbon nanotube networks for flexible Zn–air batteries

Abstract Recently, the development of high-performance bifunctional oxygen catalysts integrated with flexible conductive scaffolds for rechargeable metal-air batteries has attracted considerable interest, driving by fast-growing wearable electronics. Herein, we report a flexible bifunctional oxygen catalyst thin film consisting of Co–N–C bifunctional catalysts embedding in carbon nanotube (CNT) networks. The catalyst is readily prepared by pyrolysis of cobalt-based zeolitic imidazolate frameworks (ZIF-67) that are in-situ synthesized in CNT networks. Such catalyst film demonstrates very high catalytic activities for oxygen reduction (onset potential: 0.91 V, and half-wave potential: 0.87 V vs. RHE) and oxygen evolution (10 mA cm−2 at 1.58 V) reactions, high methanol tolerance property, and long-term stability (97% current retention). Moreover, our integrated catalyst film shows very good structure flexibility and robustness. Based on the obtained film air electrodes, flexible Zn–air batteries demonstrate low charging and discharging overpotentials (0.82 V at 1 mA cm−1) and excellent structure stability in the bending tests. These results indicate that presently reported catalyst films are potential air electrodes for flexible metal–air batteries.