Air Cathode Research Articles

Study on failure mechanism on rechargeable alkaline zinc-Air battery during charge/discharge cycles at different depths of discharge.

Background: Zinc-air battery (ZAB) is a promising candidate for energy storage, but the short cycle life severely restricts the wider practical applications. Up to date, no consensus on the dominant factors affecting ZABs cycle life was reached to help understanding how to prolong the ZAB's cycle life. Here, a series of replacement experiments based on the ZAB were conducted to confirm the pivotal factors that influence the cycle life at different depths of discharge (DOD). Method: The morphology and composition of the components of the battery were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical titration analyses. Result: SEM images and XRD results revealed that the failure of the zinc anode gradually deepens with the increase of DOD, while the performance degradation of the tricobalt tetroxide/Carbon Black (Co3O4/CB) air cathode depends on the operating time. The concentration of CO3 2- depends on the charge/discharge cycle time. The replacement experiments results show that the dominant factors affecting the ZAB's cycle life is the reduction of active sites on the surface of Co3O4/CB air cathode at a shallow DOD, while that is the carbonation of the electrolyte at a deep DOD. The reduction of active sites on the surface of Co3O4/CB air cathode is caused by the coverage of K2CO3 precipitated by carbonation of the electrolyte, suggesting that the carbonation of the alkaline electrolyte limits ZAB's cycle life. Conclusion: Therefore, this work not only further discloses the failure mechanism of ZAB, but also provides some feasible guidance to design a ZAB with along cycle life.

Ultrahigh-Loaded Fe Single Atoms and Fe3C Nanoparticle Catalysts as Air Cathodes for High-Performance Zn–Air Batteries

Fe-based materials containing Fe-Nx sites have emerged as promising electrocatalysts in the oxygen reduction reaction (ORR), but they still suffer structural instability which may lead to loss of catalytic activity. Herein, a novel electrocatalyst Fe3C-FeSA@3DCN with the coexistence of Fe3C nanoparticles and Fe single atoms (FeSA) in a three-dimensional conductive network (3DCN) is prepared via lattice confinement and defect trapping strategies with an Fe atomic loading of as high as 4.36%. In the ORR process, the limiting current density of Fe3C-FeSA@3DCN reaches 5.72 mA cm-2, with an onset potential of 0.926 V and a Tafel slope of 66 mV/decade, showing better catalytic activity and stability than Pt/C catalysts. Notably, its assembled aqueous and solid-state Zn-air batteries (ZABs) achieve peak power densities of 166 and 56 mW cm-2, respectively, with a long service life of up to 200 h at a current density of 5 mA cm-2. In addition, the assembled ZAB can provide a constant voltage on activated carbon electrodes to perform capacitive deionization to adsorb different ions. The importance of the Fe species active sites generated by Fe3C and FeSA in the material for ORR activity to boost the electron transfer and mass transfer is demonstrated by a simple selective poisoning experiment.

Flow simulation in direct ethanol fuel cells using multifunctional anode catalysts

Fuel cells have been seen as a viable alternative to fossil fuel engines, mainly driven by environmental restrictions. In this work, a direct ethanol fuel cell is modeled using a dynamic model, which considers fuel and air flow, anode and cathode losses, membrane, multifunctional catalysts (Pt/C, Pt−Ru/C and Pt−Sn/C), temperature, and the variation of species concentration in relation to the current density, since the cell operation is influenced by them. The equations are discretized using the finite difference method and the integration is performed using the Rosenbrock method. The results obtained for the flow using the dynamic model developed reasonably agree with data found in the literature. The molar fractions of the species shown contribute to the understanding of the behavior of the reactive flow that occurs inside an ethanol fuel cell.

Boric Acid‐Assisted Pyrolysis for High‐Loading Single‐Atom Catalysts to Boost Oxygen Reduction Reaction in Zn‐Air Batteries

The emerging of single‐atom catalysts (SACs) offers a great opportunity for the development of advanced energy storage and conversion devices due to their excellent activity and durability, but the actual mass production of high‐loading SACs is still challenging. Herein, a facile and green boron acid (H3BO3)‐assisted pyrolysis strategy is put forward to synthesize SACs by only using chitosan, cobalt salt and H3BO3 as precursor, and the effect of H3BO3 is deeply investigated. The results show that molten boron oxide derived from H3BO3 as ideal high‐temperature carbonization media and blocking media play important role in the synthesis process. As a result, the acquired Co/N/B tri‐doped porous carbon framework (Co–N–B–C) not only presents hierarchical porous structure, large specific surface area and abundant carbon edges but also possesses high‐loading single Co atom (4.2 wt.%), thus giving rise to outstanding oxygen catalytic performance. When employed as a catalyst for air cathode in Zn‐air batteries, the resultant Co–N–B–C catalyst shows remarkable power density and long‐term stability. Clearly, our work gains deep insight into the role of H3BO3 and provides a new avenue to synthesis of high‐performance SACs.

Fe, N, S co-doped cellulose paper carbon fibers as an air-cathode catalyst for microbial fuel cells

The heteroatoms and transition metal co-doped carbon-based catalysts are an important way to improve the catalytic activity of oxygen reduction reaction (ORR). Herein, we reported a facile method to obtain iron, nitrogen, and sulfur co-doped cellulose paper carbon fibers as catalysts (Fe–N–S/CFs) for ORR in microbial fuel cells (MFCs) with the adsorption recovery of Congo red molecules from dye wastewater. The thermal treatment promoted the etching of carbon surface by ferric ions, resulting in increased surface roughness for forming the defective carbon structure. The rich active species and defective carbon formed on the etched surface to enhance the electroactive surface area and effective sites. Fe–N–S/CFs catalysts achieved high half-wave potential due to the synergy effect between chemical components and defect structures. The assembled single-chamber air cathode MFC gained a high maximum power density of 1773 ± 40 mW m−2 versus Pt/C MFC of 1325 ± 94 mW m−2. This work provides a strategy for recovering dye molecules from wastewater to prepare non-precious metal catalysts for enhancing ORR activity.

Energy efficient portable air cathode electrochlorinator for point-of-use disinfection of toilet wastewater

Active chlorine is the most widely used disinfectant for water disinfection as well as surface sterilization. Here, we report an air cathode electrochlorinator for point-of-use disinfection of toilet wastewater. The air cathode dominated by a four-electron pathway to reduce O2 to OH- was more suitable for chlorine synthesis than through a two-electron pathway to H2O2, which could reduce chlorine back to chloride ions. The minimum driving potential of the air cathode electrochlorinator was as low as 0.94 V, which made it possible to be directly powered by a piece of commercial mini photovoltaic solar panel without electronic converter. Under the cell voltage of 2 V, the Faraday current efficiency was 82.0 % and the electrical energy required to produce 1 kg active chlorine was estimated to be only 1.75 kWh. The normalized energy consumption to disinfect simulated toilet wastewater with a pathogen concentration of 107 CFU/mL was estimated to be 7.2 W h/m3. Moreover, the material cost for fabrication of the electrochlorinator was estimated to be less than $ 0.62. These features guarantee the air cathode electrochlorinator of high potential for point-of-use disinfection of toilet wastewater.

Ordered mesoporous carbon fiber bundles with high-density and accessible Fe-NX active sites as efficient ORR catalysts for Zn-air batteries

Fe-NX/C electrocatalysts have aroused extensive interest in accelerating sluggish oxygen reduction reaction (ORR) kinetics as potential alternatives to platinum catalysts in rechargeable Zn-air batteries (ZABs). However, the low density and poor accessibility of Fe-NX sites have severely restricted the electrocatalytic performance of Fe-NX/C. Herein, Fe, N co-doped ordered mesoporous carbon fiber bundles are prepared through a ligand-assisted strategy with nitrogen-rich 1,10-phenanthroline as space isolation agent. 1,10-Phenanthroline reveals a six-membered heterocyclic structure containing abundant nitrogen species to tightly coordinate with Fe ions, which is conducive to achieving high-density Fe-NX sites. Meanwhile, the adoption of SBA-15 as hard-templates enables the catalysts with highly ordered channels and large specific surface areas, improving the accessibility of Fe-NX sites. The optimal catalyst (PDA-Fe-900) demonstrates a positive half-wave potential of 0.84 V (vs. RHE) in alkaline solution, outperforming the commercial Pt/C (0.83 V). In addition, PDA-Fe-900 delivers comparable ORR performance to commercial Pt/C in acidic electrolyte. Impressively, when PDA-Fe-900 is employed as an air cathode, it achieves large power densities of 163.0 mW/cm2 in liquid-state ZAB and 116.6 mW/cm2 in the flexible solid-state ZAB. This work provides an efficient ligand-assisted pathway for fabricating catalysts with dense and accessible Fe-NX sites as high-performance ORR electrocatalysts for ZABs.

A novel feature susceptibility approach for a PEMFC control system based on an improved XGBoost-Boruta algorithm

Data-driven modelling methods are being developed in the quest to achieve more accurate performance prediction of protons exchange membrane fuel cell (PEMFC) systems in response to their complicated physicochemical phenomena. However, there is little research in this field detailing the pre-processing and selection of balance of plants (BOP) features for the input layer of system performance prediction at different current densities. Furthermore, most of the previous research applies neural networks based on simulation data rather than real-time bench or vehicle operation datasets which leads to low robustness and unreliable practical results. This paper details the application of a novel algorithm denoted XGBoost-Boruta, which utilises the combination of an ensemble learning approach and a wrapping approach, to improve the robustness of feature selection and to increase the accuracy and robustness of PEMFC system performance prediction. By introduction of the Z score and shadow features to eliminate the randomness of conventional ensemble learning methods, seven key controllable BOP variables of the hydrogen anode, air cathode and cooling subsystems are selected as the original input variables to determine their dependency on the stack voltage. Two case studies are presented for verification and validation of the proposed algorithm based on the real-time dataset of bench experimental data and data obtained from heavy truck operation at current densities ranging from 100 to 1500 mA/cm2. The feature selection strategy, based on the proposed XGBoost-Boruta algorithm, largely decreases the RMSE by 23.8% and 14.1% and the R2 increases by 0.06 and 0.04 of both the bench experimental and the heavy truck validation datasets respectively.

Collaborative integration of ultrafine Fe2P nanocrystals into Fe, N, P-codoped carbon nanoshells for highly-efficient oxygen reduction

The rational design and facile synthesis of cost-effective and high-performance carbon-based catalysts for oxygen reduction reaction (ORR) is of great significance but remain challenging. Herein, we report the crafting of a robust Fe,N,P-codoped, ultrafine Fe2P nanocrystals decorated, highly hierarchical porous carbon nanoshells (denoted Fe,N,P-CNSs/Fe2P) via a simple yet robust one-step synergetic phosphorization and pyrolysis approach for highly-efficient ORR. Specifically, well-defined polypyrrole-co-polyaniline hollow nanospheres with a shell thickness of ≈ 43 nm (PPy-co-PANI-HNs) are first elaborately synthesized via a facile soft-templating (Triton X-100 micelles) copolymerization of pyrrole and aniline monomers. Subsequent one-step synergetic phosphorization and pyrolysis of PPy-co-PANI-HNs pre-impregnated with NaH2PO2·H2O and FeCl3 (H2PO2-,Fe3+@PPy-co-PANI-HNs) yields Fe,N,P-CNSs/Fe2P with a well-crafted ultrathin nanoshell (shell thickness of ≈13 nm) architecture containing abundant hierarchical porosity. Remarkably, an alkaline electrolyte capitalizing on the resulting Fe,N,P-CNSs/Fe2P manifests excellent ORR performance with the half-wave and onset potentials (E1/2 of 0.854 V and Eonset of 0.955 V) comparable to Pt/C, diffusion limited current density (JL of −5.98 mA cm−2) higher than Pt/C, and long-time durability and methanol resistance better than Pt/C, demonstrating great potential as air cathode in zinc-air batteries (maximum power density of 170 mW cm−2 and specific capacity of 824.5 mA h g−1). Combined experimental and theoretical studies reveal that the impressive ORR performance of Fe,N,P-CNSs/Fe2P originates from simultaneous compositional (i.e., Fe,N,P-codoping and ultrafine Fe2P nanocrystals decorating) and structural (i.e., hierarchically porous ultrathin nanoshell architecture) tailoring enabled by the judicious one-step synergetic phosphorization and pyrolysis.

Three-dimensional hierarchical flower-like bimetallic–organic materialsin situgrown on carbon cloth and doped with sulfur as an air cathode in a microbial fuel cell

Herein, the output power density produced by Zn/Co-S-3DHFLM as the cathode catalyst of an MFC was higher than that of Co-3DHFLM.

Recent advances in zinc-air batteries: self-standing inorganic nanoporous metal films as air cathodes.

Zinc-air batteries (ZABs) have promising prospects as next-generation electrochemical energy systems due to their high safety, high power density, environmental friendliness, and low cost. However, the air cathodes used in ZABs still face many challenges, such as the low catalytic activity and poor stability of carbon-based materials at high current density/voltage. To achieve high activity and stability of rechargeable ZABs, chemically and electrochemically stable air cathodes with bifunctional oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) activity, fast reaction rate with low platinum group metal (PGM) loading or PGM-free materials are required, which are difficult to achieve with common electrocatalysts. Meanwhile, inorganic nanoporous metal films (INMFs) have many advantages as self-standing air cathodes, such as high activity and stability for both the ORR/OER under highly alkaline conditions. The high surface area, three-dimensional channels, and porous structure with controllable crystal growth facet/direction make INMFs an ideal candidate as air cathodes for ZABs. In this review, we first revisit some critical descriptors to assess the performance of ZABs, and recommend the standard test and reported manner. We then summarize the recent progress of low-Pt, low-Pd, and PGM-free-based materials as air cathodes with low/non-PGM loading for rechargeable ZABs. The structure-composition-performance relationship between INMFs and ZABs is discussed in-depth. Finally, we provide our perspectives on the further development of INMFs towards rechargeable ZABs, as well as current issues that need to be addressed. This work will not only attract researchers' attention and guide them to assess and report the performance of ZABs more accurately, but also stimulate more innovative strategies to drive the practical application of INMFS for ZABs and other energy-related technologies.

Bamboo derived N-doped carbon as a bifunctional electrode for high-performance zinc–air batteries

A bamboo derived N-doped carbon displayed superior ORR/OER activity and successfully served as a bulk-phase air cathode for a rechargeable zinc–air battery.

Sustainable zinc-air battery chemistry: advances, challenges and prospects.

Sustainable zinc-air batteries (ZABs) are considered promising energy storage devices owing to their inherent safety, high energy density, wide operating temperature window, environmental friendliness, etc., showing great prospect for future large-scale applications. Thus, tremendous efforts have been devoted to addressing the critical challenges associated with sustainable ZABs, aiming to significantly improve their energy efficiency and prolong their operation lifespan. The growing interest in sustainable ZABs requires in-depth research on oxygen electrocatalysts, electrolytes, and Zn anodes, which have not been systematically reviewed to date. In this review, the fundamentals of ZABs, oxygen electrocatalysts for air cathodes, physicochemical properties of ZAB electrolytes, and issues and strategies for the stabilization of Zn anodes are systematically summarized from the perspective of fundamental characteristics and design principles. Meanwhile, significant advances in the in situ/operando characterization of ZABs are highlighted to provide insights into the reaction mechanism and dynamic evolution of the electrolyte|electrode interface. Finally, several critical thoughts and perspectives are provided regarding the challenges and opportunities for sustainable ZABs. Therefore, this review provides a thorough understanding of the advanced sustainable ZAB chemistry, hoping that this timely and comprehensive review can shed light on the upcoming research horizons of this prosperous area.

Ionic Covalent Organic Frameworks‐Derived Cobalt Single Atoms and Nanoparticles for Efficient Oxygen Electrocatalysis

Metal single atoms show outstanding electrocatalytic activity owing to the abundant atomic reactive sites and superior stability. However, the preparation of single atoms suffers from inexorable metal aggregation which is harmful to electrocatalytic activity. Here, ionic covalent organic frameworks (iCOFs) are employed as the sacrificial precursor to mitigate the metal aggregation and subsequent formation of bulky particles. Molecular dynamics simulation shows that iCOFs can trap and confine more Co ions as compared to neutral COFs, resulting in the formation of a catalyst composed of Co single atoms and uniformly distributed Co nanoparticles (CoSA &CoNP-10 ). However, the neutral COFs derive a catalyst composed of Co atomic clusters and large Co nanoparticles (CoAC &CoNP-25 ). The CoSA &CoNP-10 catalyst exhibits higher oxygen bifunctional electrocatalytic activities than CoAC &CoNP-25 , coinciding with the density functional theory results. Taking the CoSA &CoNP-10 as the air cathode in Zn-air batteries (ZABs), the aqueous ZAB presents a high power density of 181mWcm-2 , a specific capacity of 811mAhg-1 as well as a long cycle life of 407h at a current density of 10mAcm-2 , while the quasi-solid state ZAB displays a power density of 179mWcm-2 and the cycle life of 30h.

Transitional trimetallic alloy embedded polyacrylamide hydrogel derived nitrogen-doped carbon air-cathode for bioenergy generation in microbial fuel cell

Heterometallic carbons are popular materials for application in energy devices due to their high oxygen reduction reaction (ORR) activity and good catalytic stability. Particularly in microbial fuel cells (MFCs), Fe group metal alloys are efficient ORR catalysts. This work has embedded different metallic alloy nanoparticles in polyacrylamide hydrogel derived in-situ nitrogen-doped carbon. All the catalysts (Fe@NC, FeCo@NC, FeNi@NC, and FeCoNi@NC) are used as air cathodes and examined for power generation in single chamber MFCs. Trimetallic composite (FeCoNi@NC) performed better than Pt/C. FeCoNi@NC exhibited superior electrocatalytic activity with an oxygen reduction peak at 0.394 V (vs RHE) and a corresponding peak current density of −0.159 mA. FeCoNi@NC records maximum power output of 963.5 mW m−2 at 2483.2 mA m−2, 3.287 and 1.136 times higher than NC and 10 wt% Pt/C, respectively. This could be due to the uniformly distributed alloy nanoparticles, abundant pyridinic-N, and M−Nx sites that enhance the durability, charge transfer, and power generation in MFCs. These findings suggest that the trimetallic transition metal-carbon (MNC) electrodes could be promising ORR catalysts, justifying their application for energy devices.

Single-Atomic Zn/Co-Nx Sites Boost Solid-Soluble Synergistic Catalysis for Lithium-Oxygen Batteries.

Lithium-oxygen batteries have attracted widespread attention owing to their superior theoretical energy density. However, they are obstructed by sluggish oxygen reduction (ORR) and evolution reaction (OER) kinetics at air cathodes. Herein, different from using single solid or soluble catalysts, solid-soluble synergistic catalysis is proposed to conjointly enhance ORR/OER performances. During discharge, single-atomic zinc/cobalt embedded in nitrogen-doped carbon (Zn, Co-N/C) is judiciously engineered as a solid catalyst to regulate the growth pathway of Li2O2 and promote ORR kinetics. During charge, a typical redox mediator (RM, LiI) is added as a soluble catalyst to permit efficient oxidation of Li2O2. Of note is that the atomic Zn/Co-Nx sites can chemically adsorb oxidized iodine (I2) and accelerate OER kinetics, which plays a decisive role in eliminating the shuttle effect of I3-/I2 to the Li anode. Coupling a single-atomic catalyst with restricted oxidized iodine offers an exceptional discharge capacity, remarkably low polarization, and superior long-term cycling stability.

Hybrid Carbon Sphere Chain-MnO2 Nanorods as Bifunctional Oxygen Electrocatalysts for Rechargeable Zinc-Air Batteries.

It is now recognized that the development of self-supported and efficient bifunctional air cathodes via the direct growth of earth-abundant catalysts onto the surface of the conductive collector would be a cutting-edge strategy to reduce interfacial resistance, enhance the mechanical tenure, and reduce the final weight and cost of manufacturing of rechargeable Zn-air batteries (ZABs). This work reports an innovative self-supported precious metal-free electrode, comprising carbon sphere chains (CSCs) directly grown onto a carbon paper (CP) substrate, wherein the CSCs have a functionalized surface bearing carbon nanobud defects, oxygen functional groups, and high-density MnO2 hierarchical nanorods (NRs), uniformly coating the surface of CSCs. Not only is the metal-free functionalized CSC catalyst functional for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) but its combination with MnO2 NRs impressively enhances the ORR/OER activities. A homemade ZAB assembled with functionalized CSC/MnO2 air cathode can successfully power a timer for a period of 17 days with no voltage loss, whereas two series-connected ZABs can light up 39 red light-emitting diode (LED) bulbs. The self-supported and earth-abundant-based CSC/MnO2 materials open up an opportunity for lightweight and cost-effective ZABs and metal-air batteries in general.

Highly-dispersed NiFe alloys in-situ anchored on outer surface of Co, N co‑doped carbon nanotubes with enhanced stability for oxygen electrocatalysis

Transition metal alloys have emerged as promising catalysts for oxygen reduction/evolution reactions (ORR/OER) because of their intermetallic synergy and tunable redox properties. However, for alloy nanoparticles, it is quite challenging to suppress the self-aggregation and promote the bifunctional activity. Anchoring alloys in heteroatoms-doped carbon matrix with excellent electro-conductibility is a powerful strategy to form strongly-coupled alloy-carbon nanohybrids. Here, highly-dispersed NiFe alloys are evenly in-situ anchored on the surface of Co, N co-doped carbon nanotubes (NiFe/Co-N@CNTs) via a gravity-guided chemical vapor deposition and self-assembly strategy. Stably-structured NiFe/Co-N@CNTs possesses a tubular skeleton with diameters of 80–100 nm and a hydrophilic surface. For ORR, half-wave potential of NiFe/Co-N@CNTs (0.87 V vs RHE) is higher than that of Pt/C (0.85 V). Strong synergies between NiFe alloys and Co-Nx species facilitate the charge transfer on one-dimensional conductive structure to boost the 4e- ORR kinetics. For OER, NiFe/Co-N@CNTs has a lower overpotential (300 mV) than RuO2 (400 mV) at 10 mA cm−2 due to in-situ formation of highly-active NiOOH/FeOOH species (as indicated by in-situ X-ray diffraction) at the catalytic sites on NiFe alloy. Rechargeable Zn-air battery (ZAB) with NiFe/Co-N@CNTs-based air–cathode exhibits promising open-circuit potential (1.52 V) and charge–discharge cycling stability (350 h). This alloy-carbon integrating strategy is meaningful for promoting dispersion, activity and stability of non-noble metal alloys for oxygen electrocatalysis.

Amplifying power generation in microbial fuel cells with cathode catalyst of graphite-based nanomaterials

Low catalytic activity, scarcity of resources, design complexity, high cost, and unfavourable nature of non-traditional metal and its composites limit their utilization as cathodes in microbial fuel cells (MFCs). This research aimed to identify the most effective new cathode catalyst for use in one chamber air cathode microbial fuel cells by comparing two graphite-based nanomaterials of Reduced Graphene Oxide Hydrogen iodide - Acetic acid (rGOHI-AcOH) and Reduced Graphite Oxide Nickel Nanoparticles (rGO/Ni) composite. The behavior of microbial fuel cells was calculated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Since the rGOHI-AcOH cathodes were more efficient, the MFCs produced maximum power (>37%) than the rGO/Ni Nanoparticles cathode MFCs. The double loading (DL) rGOHI-AcOH cathodes in the Microbial Fuel Cells produced the maximal power densities at 1691 ± 34 mW/m2 (CE = 73 ± 5%), covering 78% of the power densities calculated for Platinum/Carbon (Pt/C) (2203 ± 52 mW/m2; CE = 82 ± 3%). With a double catalyst load, MFCs using rGO/Ni Nanoparticles composite anodes produced more power than the others (1016 ± 31 mW/m2, CE = 71 ± 3%). Excellent concordance was seen between CV and EIS and the MFC findings. Based on the results of this research, the rGOHI-AcOH cathode loaded with two catalysts has the potential to produce long-lasting, environmentally friendly materials at low cost and maintain consistent power output and the reliable operation of MFCs throughout their useful lifetimes.

Boosting electrocatalytic oxygen reduction performance of Co[sbnd]N[sbnd]C catalysts on Ti3C2 MXene by the synergistic effect with oxygen vacancy-rich TiO2

Construction of multiphase nanocomposites is an effective way to develop high performance oxygen reduction catalysts. Herein, Ti3C2 MXene supported CoNC and oxygen vacancy-rich TiO2 (ov-TiO2) composite catalyst (CoNC/TiO2-Ti3C2) is prepared by coordination and polymerization of dopamine and Co2+ on the surface of Ti3C2 nanosheets and subsequent heating treatment. The oxygen vacancies on the surface of TiO2 nanoparticles can stabilize the CoNC catalysts as well as promote the oxygen reduction reaction (ORR) on them. Therefore, CoNC/TiO2-Ti3C2 exhibits good ORR activity and durability, even better than the commercial Pt/C catalyst. In contrast, Ti3C2 supported CoNC catalyst without ov-TiO2 (CoNC/Ti3C2) shows decreased ORR activity, indicating the significance of the synergistic effect of CoNC and ov-TiO2. In a practical application, CoNC/TiO2-Ti3C2 exhibits a large power density (155.3 mW cm−2) and extraordinary long-term rechargeability as the air cathode for Zn-air batteries. This strategy of in-situ growth of cocatalysts on Ti3C2 MXene provides a new way for the preparation of high-performance non-noble metal catalysts.