Continuous Charge Research Articles

In Situ Prepared Three-Dimensional Covalent and Hydrogen Bond Synergistic Binder to Boost the Performance of SiOx Anodes for Lithium-Ion Batteries

Polymer binders play an important role in enhancing the electrochemical performance of silicon-based anodes to alleviate the volume expansion for lithium-ion batteries. It is difficult for common one-dimensional (1D) linear binders to limit the volume expansion of a silicon-based electrode when combined with silicon-based particles with scant binding points. Therefore, it is necessary to design a three-dimensional (3D) network structure, which has multiple binding points with the silicon particles to dissipate the mechanical stress in the continuous charge and discharge circulation. Here, a covalent and hydrogen bond synergist 3D network green binder (poly(acrylic acid) (PAA)-dextrin 9 (Dex9)) was prepared by the simple in situ thermal condensation of a one-dimensional liner binder PAA and Dex in the electrode fabrication process. The optimized SiOx@PAA-Dex9 electrode exhibits an initial Coulombic efficiency (ICE) of 82.4% at a current density of 0.2 A g-1. At a high current density of 1 A g-1, it retains a capacity of 607 mAh g-1 after 300 cycles, which is approximately twice as high as that of the SiOx@PAA electrode. Furthermore, the results of in situ electrochemical dilatometry (ECD) and characterization of electrode structures demonstrate that the PAA-Dex9 binder can effectively buffer the huge volume change and maintain the integrity of the SiOx electrodes. The research overcomes the low electrochemical stability difficulty of the 3D binder and sheds light on developing the simple fabrication procedure of an electrode.

Semi-Polycrystalline Polyaniline-Activated Carbon Composite for Supercapacitor Application.

We report on the synthesis of activated carbon-semi-polycrystalline polyaniline (SPani-AC) composite material using in-situ oxidative polymerization of aniline on the carbon surface in an aqueous HCl medium at an elevated temperature of 60 °C. The electroactive polymeric composite material exhibits a uniformly distributed spindle-shaped morphology in scanning electron microscopy (SEM) and well-defined crystallographic lattices in the high-resolution transmission electron microscopy (TEM) images. The X-ray diffraction (XRD) spectrum reveals sharp peaks characteristic of crystalline polyaniline. The characteristic chemical properties of polyaniline are recorded using laser Raman spectroscopy. The cyclic voltammetry curves exhibit features of surface-redox pseudocapacitance. The specific capacitance calculated for the material is 507 F g-1 at the scan rate of 10 mV s-1. The symmetrical two-electrodes device exhibits a specific capacitance of 45 F g-1 at a current density of 5 A g-1. The capacitive retention calculated was found to be 96% up to 4500 continuous charge-discharge cycles and observed to be gradually declining at the end of 10,000 cycles. On the other hand, Coulombic efficiency was observed to be retained up to 85% until 4500 continuous charge-discharge cycles which declines up to 72% at the end of 10,000 cycles. The article also presents a detailed description of material synthesis, the formation of polyaniline (Pani) chains, and the role of material architecture in the performance as surface redox supercapacitor electrode.

Investigation of Different Aqueous Electrolytes for Biomass-Derived Activated Carbon-Based Supercapacitors

The present work reports the synthesis of biomass derived activated carbon and its electrochemical behaviour in different electrolytes. Ricinus communis shell (RCS) was used as a raw material in this study for the synthesis of activated carbon (AC) following a high-temperature activation procedure using potassium hydroxide as the activating agent. The physical and structural characterization of the prepared Ricinus communis shell-derived activated carbon (RCS-AC) was carried by Brunauer-Emmett-Teller analysis, X-ray diffraction analysis, Fourier Transform Infrared Spectroscopy, Raman Spectroscopy and Scanning Electron Microscopy. The synthesized AC was electrochemically characterized using various techniques such as Cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) tests, and Electrochemical impedance spectroscopy (EIS) measurements in different aqueous electrolytes (KOH, H2SO4, and Na2SO4). The results show that the double layer properties of the RCS-AC material in different electrolytes are distinct. In specific, the working electrode tested in 3 M KOH showed excellent electrochemical performance. It demonstrated a specific capacitance of 137 F g−1 (at 1 A g−1 in 3 M KOH) and exhibited high energy and power densities of 18.2 W hkg−1 and 663.4 W kg−1, respectively. The observed capacitance in 3 M KOH remains stable with 97.2% even after 5000 continuous charge and discharge cycles, indicating long-term stability. The study confirmed that the synthesized RCS-derived activated carbon (RCS-AC) exhibits good stability and physicochemical characteristics, making them commercially promising and appropriate for energy storage applications.

Design of high-performance triboelectric-piezoelectric hybridized mechanical energy harvester inspired by three-phase asynchronous generator

Hybridized nanogenerators harvesting ambient mechanical energy via multiple energy conversion mechanisms is attractive for the development of next-generation energy sources. However, existing devices are still restricted in device size, structure complexity, power circuit and energy utilization scheme. Herein, inspired by the principle of three-phase asynchronous generator, we designed a triboelectric-piezoelectric hybridized mechanical energy harvester (HMEH) that tightly combines triboelectric and piezoelectric components in all-in-one package. Through the strategy of three-phase full-wave rectifier and integration of triboelectric/piezoelectric components with similar impedance to optimize the power extraction, one HMEH device can deliver remarkable outputs of 810 V and 0.65 mA at excitation frequency of 0.5 Hz, and even up to 1.10 mA at 4.0 Hz. The device also can endure 40,000 contact-separation cycles stability tests with no device failure and little outputs decay, demonstrating its excellent durability and reliability. The power density of this HMEH device approaches a high value of 1.02 mW cm−2 among similar contact-separation mode HNGs reported to date. Scalable performance of ∼4 mA can be obtained through the 2 × 2 HMEH arrays, supplying power for a smart band in sensing of heart rate and transmitting data wirelessly. The continuous charging of supercapacitor and lithium battery through HMEH arrays are demonstrated, providing extended energy utilization schemes for pulse-power and constant-power types electronics. This work can provide new insights in designing high-performance hybridized mechanical energy harvester and facilitate the development of power-generating technologies in further real-life applications, such as smart road infrastructures, wearable electronics and large-scale blue energy.

Migration electric-field assisted electrocoagulation with sponge biochar capacitive electrode for advanced wastewater phosphorus removal

Migrating electric field-assisted electrocoagulation (MEAEC) is a three-electrode electrochemical system, including waste flour-derived sponge biochar (SBC) as an adsorption electrode for efficient phosphorus removal from wastewater. The SBC was applied in the MEAEC system as a pseudo capacitance electrode with low energy consumption and reached an excellent effluent level (0.12 mg/L) with a 200-s treatment time in 1 mg/L phosphate synthetic wastewater. The SBC adsorption electrode had a total charge capacitance of 1.14 F/g with abundant micropores. Continuous charging and discharging at a constant voltage over 100 cycles demonstrated the excellent durability of the biochar electrodes. The energy demand of SBC-MEAEC was only 0.0058 kWh/m3 for 90% phosphate removal, which was 65% less than that of the control. The use of SBC in the MEAEC system greatly enhanced phosphate removal at low concentrations. In the SBC-MEAEC system, the electro-desorption synchronous electrocoagulation process demonstrated efficient concentration and release of ions after electro-adsorption. These results indicate that MEAEC with an SBC electrode could achieve a high level of phosphate removal with a much lower energy consumption than in previous studies. The recovered concentrated phosphorus flocs also contained fewer metal impurities than those in previous electrochemical approaches. The proposed desorption synchronous electrocoagulation utilizing waste-derived SBC electrodes provides a cost-effective pathway to treat low phosphorous-containing wastewater.

Microwave-Assisted Hierarchically Grown Flake-like NiCo Layered Double Hydroxide Nanosheets on Transitioned Polystyrene towards Triboelectricity-Driven Self-Charging Hybrid Supercapacitors.

Recently, there is a need to explore the utilization of various heterostructures using the designed nanocomposites and tuning the surfaces of electrodes for improving the electrochemical performance of supercapacitors (SC). In this work, a novel approach is successfully employed through a facile two-step synthetic route with the assistance of a microwave for only 1 min. Depending on the glass transition of a polystyrene (PS) substrate and electrochemical deposition (ECD) of electroactive Ni-Co layered double hydroxides (LDHs), a hierarchically designed flake-like morphology can be readily prepared to enhance the surface-active sites, which allows a rhombohedral Ni-Co LDHs electrode to obtain superior electrochemical properties. Further, the interactions between electrode and electrolyte during the diffusion of ions are highly simplified using multiple enhanced electroactive sites and shorter pathways for electron transfer. The unique surface architecture of the PS substrate and the synergistic effect of the bimetallic components in Ni-Co LDHs enable this substrate to obtain desired electrochemical activity in charge storage systems. The optimized MWC Co0.5Ni0.5 electrode exhibited an areal capacity of 100 µAh/cm2 at a current density of 1 mA/cm2 and a remarkable capacity retention of 91.2% over 5000 continuous charging and discharging cycles due to its remarkable synergistic effect of abundant faradaic redox reaction kinetics. The HSC device is assembled with the combination of optimized MWC Co0.5Ni0.5 and activated carbon as a positive and negative electrode, respectively. Further, the electrochemical test results demonstrated that MWC Co0.5Ni0.5 //AC HSC device showed a high areal capacitance of 531.25 mF/cm2 at a current density of 5 mA/cm2. In addition, the fabricated an aqueous HSC device showed a power density of 16 mW/cm2 at an energy density of 0.058 mWh/cm2, along with the remarkable capacity retention of 82.8% even after 10,000 continuous charging and discharging cycles. Moreover, the assembled hybrid supercapacitor (HSC) device is integrated with a triboelectric nanogenerator (TENG) for the development of energy conversion and storage systems. Not only an extensive survey of materials but also an innovative solution for recent progress can confirm the wide range of potential SC applications. Remarkably, this study is a new way of constructing self-powered energy storage systems in the field of sustainable wearable electronics and future smart sensing systems.

Continuous charge management scheme for TianQin

TianQin is a proposed Chinese space-borne gravitational wave detection mission, which will consist of three earth-orbiting spacecraft in equilateral triangle constellation. Due to the ‘3 months on + 3 months off’ observation scheme, the continuous scientific observation period of TianQin is much shorter than LISA, it is highly preferred that other on-board operations, such as charge management, will not interrupt gravitational wave detection. This paper presents a torsion pendulum system on the ground to investigate the continuous discharge method in detail. It is found that the difference in surface characteristics between the test mass and the surrounding housing is the most critical to the success of continuous discharge method. Consequently, the effect of this difference on the continuous discharge process was evaluated in ground simulation experiments, and based on the research results, we also proposed a more feasible spatial continuous charge management strategy for TianQin.

Performance of supercapacitors with RuO2 electrodes spray deposited with aqueous/organic solvent mixtures: effect of substrate temperature

ABSTRACT RuO2 electrodes were spray-deposited utilizing an aqueous/organic solvent mixture at varied substrate temperatures. X-ray diffraction data supported the rutile structure and tetragonal phase of RuO2. FESEM images showed a porous structure with small spherical grains covering the entire substrate surface. Optical studies have shown that RuO2 films have bandgaps between 1.90 and 2.13 eV. Electrical resistivity was found in the range of 0.57 × 104 Ω-cm to 1.23 × 104 Ω-cm. CV (scan rate 5 mVs−1) results confirmed the specific capacitances of 560, 637, 687, 602 and 527 Fg−1 at substrate temperatures of 250, 275, 290, 300 and 325°C, respectively, in 0.5 M H2SO4 electrolyte. RuO2 provided a high specific capacitance 741 Fg−1 (current density 0.5 Ag−1) from GCD profile besides good specific capacitance holding of 87.66% over 3000 continuous charge–discharge cycles. The results show that RuO2 films spray deposited with aqueous/organic solvent mixtures give the best results.

Grid Side Distributed Energy Storage Cloud Group End Region Hierarchical Time-Sharing Configuration Algorithm Based on Multi-Scale and Multi Feature Convolution Neural Network

There is instability in the distributed energy storage cloud group end region on the power grid side. In order to avoid large-scale fluctuating charging and discharging in the power grid environment and make the capacitor components show a continuous and stable charging and discharging state, a hierarchical time-sharing configuration algorithm of distributed energy storage cloud group end region on the power grid side based on multi-scale and multi feature convolution neural network is proposed. Firstly, a voltage stability analysis model based on multi-scale and multi feature convolution neural network is constructed, and the multi-scale and multi feature convolution neural network is optimized based on Self-Organizing Maps (SOM) algorithm to analyze the voltage stability of the cloud group end region of distributed energy storage on the grid side under the framework of credibility. According to the optimal scheduling objectives and network size, the distributed robust optimal configuration control model is solved under the framework of coordinated optimal scheduling at multiple time scales; Finally, the time series characteristics of regional power grid load and distributed generation are analyzed. According to the regional hierarchical time-sharing configuration model of “cloud”, “group” and “end” layer, the grid side distributed energy storage cloud group end regional hierarchical time-sharing configuration algorithm is realized. The experimental results show that after applying this algorithm, the best grid side distributed energy storage configuration scheme can be determined, and the stability of grid side distributed energy storage cloud group end region layered time-sharing configuration can be improved.

Investigations of Lithium-Ion Battery Thermal Management System with Hybrid PCM/Liquid Cooling Plate

To improve the operating performance of the large-capacity battery pack of electric vehicles during continuous charging and discharging and to avoid its thermal runaway, in this paper we propose a new hybrid thermal management system that couples the PCM with the liquid cooling plate with microchannels. The flow direction of the microchannel structure in the bottom plate is designed according to the characteristics of the large axial thermal conductivity of the battery, and the cooling performance of the whole system under continuous charge/discharge cycles is numerically simulated. The results show that the hybrid PCM/liquid cooling plate can maintain good cooling performance under the discharge process of a large-capacity battery pack. After each cycle the temperature of the battery pack can be reduced to less than 30°, and the maximum temperature change rate of multiple cycles is controlled within 0.8%. With the application of the hybrid PCM/liquid-cooled plate battery cooling system, a safe temperature range of the battery pack is ensured even under multiple cycles of charging and discharging. The present work can facilitate future optimizations of the thermal management system of the large-capacity battery pack of electric vehicles.

An eccentric-structured hybrid triboelectric-electromagnetic nanogenerator for low-frequency mechanical energy harvesting

With the increasing aggravation of the environmental pollution and energy crisis, exploiting clean and renewable energy becomes imperative for human existence and development. In this paper, an eccentric-structured hybrid triboelectric-electromagnetic nanogenerator (EHNG) is proposed to harvest low-frequency mechanical energy. It mainly contains two parts, – a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG). Exploiting the unique eccentric structure, the EHNG can effectively transfer one-dimensional mechanical motion of an object to the rotation of the eccentric rotor, resulting in electricity generation. In comparison to a separate energy harvesting unit, the hybrid nanogenerator operates beyond the single energy harvesting mode, showing preferable electrical output performances including a broader output range and shorter time of voltage boosting. In terms of energy storage, the EHNG provides not only a higher saturation charging voltage and continuous charging from the TENG part, but also a rapid charging speed in the early charging phase from the EMG part. As a practical power source, the EHNG is shown to be capable of directly powering LEDs. The present work develops an effective and sustainable technique to maximally harvest mechanical energy from the environment.

Nanoporous Carbon/Cobalt Composite Derived from End-of-Life Lithium Cobalt Oxide-Type Lithium-Ion Batteries for Supercapacitor Applications

A simple, effective, and environment-friendly recycling process has been designed to recover cobalt as a nanoporous carbon/cobalt (NPC@Co) composite from the electrode black powder of spent lithium cobalt oxide-type (LiCoO2 cathode-based) lithium-ion batteries (LIBs). In this process, citric acid is used as a lixiviant to leach the cobalt and lithium into the aqueous solution. Furthermore, the dissolved cobalt was precipitated as a cobalt-based metal–organic framework (ZIF-67) at room temperature. Finally, as-recovered ZIF-67 was annealed at 700 °C for 8 h under a nitrogen atmosphere to synthesize the NPC@Co composite. The electrochemical behavior of the NPC@Co composite was also investigated in the 1 M H2SO4 electrolyte. This composite electrode delivers a specific capacitance of 160 F g–1 at a current density of 1 A g–1 within a potential window of 0–1 V. The NPC@Co composite also showed good stability and retained approximately 83.76% of its initial capacity after 5000 continuous charge–discharge cycles.

Ionic liquid etched and microwave-assisted delaminated MXene as an excellent electrocatalyst for the hysteretic negative reaction of vanadium redox flow batteries

The reaction kinetics of V3+/V2+ redox couple in VRFBs are relatively lagging behind, thus developing excellent electrocatalyst to enhance the negative reaction kinetics is more efficient to improve the battery performance. In this work, a novel IL-MW-MXene with unique 2D structure and abundant active functional groups is prepared easilyandeffectively by ionic liquid etching and microwave-assisted stripping, which is proposed as a promising electrocatalyst for the V3+/V2+ redox reactions. The morphology, structure and surface element composition are systematically investigated. Carbon fibers felt covered with this novel 2D-MXene flake exhibits improved hydrophilicity and electrocatalytic activity towards the V3+/V2+ redox reactions. And the single VRFB with IL-MW-MXene/CF composites as the negative electrode exhibits the higher energy efficiency of 83.56 % at 200 mA cm−2, which are 7.53 % higher than that with pristine CF as the negative electrode. More importantly, the energy efficiency shows no obvious attenuation over 200 continuous charge–discharge cycles, and the discharging capacity decay rate is only 0.12 % per cycle. The IL-MW-MXene exhibits good application potential in VRFBs and other electrochemical devices due to the green and highly effective preparation process and excellent electrocatalytic property.

Mechanism study of the conductivity characteristics of cellulose electrical insulation influenced by moisture

Cellulose insulating paper is widely used in the power industry for its good electrical insulating properties. Moisture sharply increases its conductivity, which directly leads to the weakening of insulation performance and greatly increases the risk of subsequent electric field distortion and insulation breakdown. This paper focuses on the microscopic mechanism of moisture changing the characteristics of charge transport in cellulose insulation and attempts to reveal the related conductivity mechanism. To achieve this purpose, microscopic and macroscopic perspectives are integrated and several simulation and experimental methods are utilized comprehensively. The molecular dynamics simulation results showed that most water molecules in damped cellulose were individually and uniformly adsorbed on the hydroxyl groups by hydrogen bond, and the quantum chemistry computation results showed that the lowest unoccupied molecular orbital more appeared on the water molecule and the corresponding density of state increased. Then, experimentally, it was confirmed that the trap energy level decreased by the thermally stimulated current method. On this basis, the promotion effect of moisture on charge transport is predicted and verified by polarization and depolarization current methods. As the moisture content increased, more charge carriers escaped from the trap by hopping and participated in long-range continuous charge motion. Therefore, after dampness, the current of cellulose insulating paper increased exponentially with the increase in electric field strength, which was consistent with the hopping conductivity mechanism.

Manganese-based coordination framework derived manganese sulfide nanoparticles integrated with carbon sheets for application in supercapacitor

Manganese sulfide (MnS) with high specific capacitance and low-cost merits, has been investigated as a potential electroactive material for supercapacitor. However, in practical application, MnS has been suffering from some disadvantageous issues such as insufficient electrical conductivity, serious particle agglomeration as well as huge volume change during continuous charges and discharges, which resulted in a limited specific capacitance, shortened working life and inferior rate performance. Engineering electrode materials with controlled nanostructure and composition is pivotal to improve electrichemical performance of supercapacitors. This paper introduces a facile in situ sulfuration method to fabricate MnS/NSC composite with Mn-hexamethylene tetramine coordination framework as precursor. The results indicated that MnS nanoparticles were highly dispersed and incorporated into nitrogen, sulfur-doped carbon microsheets in MnS/NSC composite. Carbon matrix effectively dispersed and confined the MnS nanoparticles, thus inhibiting aggregation, relieving volume change and retaining structural integrity. Moreover, the 2D conductive carbon matrix reduced the diffusion distance for ions and ensured fast electron delivery. As a result, MnS/NSC electrode delivered a tremendously boosted electrochemical performance for supercapacitor. A large capacitance value about 1881.8F/g was achieved at 1A/g. Even cycling for 3000 loops at 40 A/g, MnS/NSC electrode retained a large capacitance of 404.3F/g. Furthermore, an asymmetric capacitor based on assembly of MnS/NSC composite cathode and activated carbon anode was fabricated. As tested under a current density of 0.1 A/g, it delivered a capacitance of ∼ 110.1F/g and achieved an energy density of 12.4 Wh kg−1 along with a power density of 3.03 kW kg−1. These results demonstrate the potential utilization of MnS/NSC composite as electrodes for energy conversion and storage devices and open up a route for material design for future energy storage devices.

Cover Feature: Continuous Charge Transport in Carbon Nitride Modulated by Interfacial Chemical Bond and Homophase Junction to Boost Photocatalytic Hydrogen Production (Chem. Eur. J. 66/2022)

Cover Feature: Continuous Charge Transport in Carbon Nitride Modulated by Interfacial Chemical Bond and Homophase Junction to Boost Photocatalytic Hydrogen Production (Chem. Eur. J. 66/2022)

Continuous Charge Transport in Carbon Nitride Modulated by Interfacial Chemical Bond and Homophase Junction to Boost Photocatalytic Hydrogen Production.

Efficient separation of photogenerated electrons and holes is of key importance in photocatalysis. Tuning the charge separation pathway is significant but still suffering from low efficiency for the charge extraction from semiconductors. Herein, taking 2D g-C3 N4 (CN) nanosheets as a model photocatalyst, it was found the decoration of homophase junction between brookite TiO2 rods and nanoparticles (BN -BR ) onto CN can effectively modulate photogenerated charge extraction and transfer in BN -BR /CN composites. The BN -BR /CN exhibits a remarkably enhanced photocatalytic H2 evolution under visible light irradiation (λ>420 nm) compared with the single component. A continuous electron transfer channel constructed by an interfacial chemical bond Ti-O-N between CN and brookite rods (BR ) and BN -BR homophase junction between brookite nanoparticles and rods was proposed to benefit the charge extraction and transfer. This work provides a strategy to tune the charge separation and transfer to facilitate the photocatalytic performance in heterogeneous photocatalysis.

Design and synthesis of NiCo-NiCoO2@C composites with improved lithium storage performance as the anode materials

The rapid capacity decay severely limits the commercial applications of metal oxide-based electrodes. Exploring innovative materials with enhanced lithium storage performance is urgent and challenging. Herein, we propose a strategy for the synthesis of NiCo-NiCoO2@C composites using layered double hydroxide (LDH) precursors. When used as the anode materials, the composites deliver enhanced capacity throughout the continuous charge–discharge process. In our design, the electrochemically active NiCoO2 nanoparticles pulverize the NiCo phases via a conversion reaction. The NiCo phases can increase capacity by reacting with the Li2O yielded from the conversion of NiCoO2 and participating in the reversible transformation of solid-electrolyte interface (SEI) films, thus ensuring fast charge transfer. Voids that appear with the consumption of NiCo phases can provide abundant channels for Li+ transportation. Carbon matrices can effectively alleviate the stress generated during repeated cycles of expansion and shrinkage. Benefiting from these features, NiCo-NiCoO2@C anode delivers a highly enhanced reversible capacity of 961.6 mAh g−1 after 300 cycles at 200 mA g−1. This LDH-based strategy may be extended to the design and synthesis of various enhanced anode materials for lithium-ion batteries (LIBs).

Calcium versus potassium selectivity in a nanopore: The effect of charge inversion at localized pore charges

The Anomalous Mole Fraction Effect (AMFE) in negatively charged pores has been considered as a signature of Ca2+ vs.monovalent ion (K+, in this study) selectivity. Increasing the mole fraction of CaCl2 in the KCl/CaCl2 mixture, the total conductance first declines as Ca2+ ions replace K+ ions inside the pore, then it increases as Ca2+ becomes the main charge carrier. While the AMFE was first pointed out in calcium selective ion channels, in a previous study (Gillespie et al., Biophys. J. 95 (2008) 609–619.) we showed that it is also present in synthetic nanopores. Here we use the Local Equilibrium Monte Carlo method coupled to the Nernst-Planck transport equation to study a simple model of a finite nanopore in a membrane with ions being explicitly modeled as charged hard spheres and water as an implicit continuum. The novel component of the model is the treatment of the pore charges that are present in localized COO− groups on the wall of the nanopore. Therefore, we study the effect of localizing the pore charges instead of smearing them as a continuous surface charge. Localized charges profoundly influence Ca2+ vs.K+ selectivity because they enhance charge inversion at the pore wall. Ca2+ ions overcharge the pore wall at which the K+ ions have a disadvantage in the K+ vs.Ca2+ competition because the overcharged pore wall does not attract them so strongly.

Two-in-one strategy to construct bifunctional oxygen electrocatalysts for rechargeable Zn-air battery

Integrating two different catalytic active sites into one composite is a useful 2-in-1 strategy for designing high-efficient bifunctional catalysts, which can easily tailor the activity of each reaction. Hence, we adopt the 2-in-1 strategy to design the metal oxyhydroxide supported on N-doped porous carbons (PA-CoFe@NPC) as the oxygen bifunctional catalyst, where NPC provides the activity for oxygen reduction reaction (ORR) while the metal oxyhydroxide is responsible for oxygen evolution reaction (OER). Results demonstrate that the PA-CoFe@NPC indeed exhibits both super ORR and OER activities. Impressively, using bifunctional PA-CoFe@NPC as the oxygen electrode, the resulting Zn-air battery exhibits outstanding charge and discharge performance with the peak power density of 156.3 mW cm–2, and also exhibits a long-term cycle stability with continuous cyclic charge and discharge of 170 hours that is obviously better than the 20% Pt/C+IrO2 based one. The 2-in-1 strategy in this work can be efficiently extended to design other bi- or multi-functional electrocatalysts.