Rechargeable Zn-air Batteries Research Articles

Bamboo fiber–derived bifunctional electrocatalyst for rechargeable Zn-air batteries

Low-cost and high-performance bifunctional electrocatalysts for efficient oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) are vital for the applications of rechargeable Zn-air batteries (ZABs). Herein, a porous carbon material is fabricated by traditional pulp and papermaking and carbonization process from bamboo. The resultant carbon paper catalyst possesses a high surface area, porous structure, and high content of nitrogen. Benefiting from these characteristics, this material exhibits remarkable ORR and OER catalytic performances. The aqueous rechargeable Zn-air batteries assembled with this catalyst exhibit a high power density of 279.5 mW cm−2. This work paves an encouraging way for the industrial production of cost-effective catalysts in a sustainable manner.

The influence of different air electrode structures to discharge characteristics in rechargeable Zn-air battery

The rechargeable metal-air battery technology is a well-interested smart method for eco-friendly and sustainable energy storage. Both of the two order of magnitude lower global market price per tonne of Zn compared to lithium and the multiple theoretical and practical specific energy density of rechargeable ZAB compared to the worldwide Li-ion designs contributes the developing continuously of rechargeable Zn-air battery. The air electrode as a cathode has a vital role in increasing the discharge-charge performance in ZABs, therefore different layers-order air electrodes were assembledwith the utilization of Ni-foam, graphite coating and carbon nanoparticles. The tri-layers cathode showed the highest voltage and performance values compared to the mono- (Ni-foam) and bi- (Ni-foam + graphite coating) layers architectures. The effect of electrolyte inorganic additives (e.g., 2 n/n% ZnCl2 and 0,05 wt% MnO2) was experienced especially at the no-load period.

CuO/Co3O4 heterostructures with carbon nanotubes composites as ORR/OER electrocatalysts for Zn-air batteries

Rechargeable Zn-air batteries (ZABs) constitute promising next-energy conversion and storage systems due to their low cost, intrinsic safety, and feasibility to fabricate high energy density and stable charge and discharge voltage. Nevertheless, the most significant challenge of rechargeable ZABs is relatively high over potential owing to the sluggish kinetics of oxygen reactions on the air cathode, requiring high-performance noble-metal-free bifunctional electrocatalysts with highly cost-effective. Herein, we developed a facile and scalable coprecipitation strategy to successfully prepare CuO/Co3O4@CNTs catalysts for bifunctional oxygen electrocatalysts. This unique strategy enables CuO/Co3O4 nanoparticles to be uniformly grown on CNTs and the simultaneous pyrolysis process results in the generation of ultrafine CuO/Co3O4 heterostructures. Contributed to an abundance of heterostructures, the oxygen vacancies and unsaturated chemical bonds in the interface were generated in CuO/Co3O4. Consequently, the CuO/Co3O4@CNTs delivered bifunctional activity of ΔE of 0.78 V and good stability that can maintain 1000 h charge and discharge cycles.

A high-voltage Zn-air battery based on an asymmetric electrolyte configuration

Rechargeable Zn-air batteries promise safe energy storage. However, they are limited by the redox potential of O2/O2- chemistry in an alkaline electrolyte, resulting in low operating voltages and therefore insufficient energy density to compete with lithium-ion batteries. The O2/O2- redox potential increases by 0.8 V in an acidic medium, hinting at a way to boost the voltage: an asymmetric electrolyte configuration decoupling acidic and alkaline electrolytes for the air cathode and zinc anode. Such configuration requires a thin and ionically conductive membrane to separate two mutually incompatible electrolytes. Here, we report a Zn ion-exchange membrane with high ionic conductivity of 1.1 mS cm-1, which prevents acid-base neutralization. The highly reversible O2/O2- reaction in the acid is made possible by compositing a cobalt-coordinated porphyrin-based polymeric framework with MXene as a bifunctional electrocatalyst. The asymmetric Zn-air battery operates at voltages up to 1.85 V and cycles for more than 200 h with a material-level energy density of 1350 Wh kg-1, projected to a high device-level energy density of 50 Wh kg-1 (coin cell diameter: 20 mm). The asymmetric configuration withstands pressure up to 4 MPa (∼1200 N), demonstrating excellent structural stability for production and practical applications.

NaCl sealing Strategy-Assisted synthesis CoO-Co heterojunctions as efficient oxygen electrocatalysts for Zn air batteries

Developing highly efficient, low-cost, and stable bifunctional oxygen electrocatalysts is essential for the wide popularization of rechargeable Zn-air batteries. Combining zero-dimensional metal nanoparticles with two-dimensional metal oxide nanosheets is an appealing strategy to balance performance and cost. However, the precise construction of these composites remains a great challenge, and their interaction mechanisms lack thorough study. Herein, a cobalt-oxide-based bifunctional oxygen electrocatalyst comprising a rich Co-CoO heterointerface (CoO/Co@NG) was synthesized via a NaCl sealing-assisted pyrolysis strategy. The NaCl crystals played the role of a closed nanoreactor, which facilitated the formation of a CoO-Co heterojunction. Experimental results and theoretical calculations confirmed that the ingeniously constructed heterojunction expedited the oxygen reduction reaction and oxygen evolution reaction kinetics, which is superior to Pt/C. When serving as the air electrode in an assembled liquid-state Zn-air battery, the battery shows high power density (215 mW cm−2), specific capacity (710 mAh gzn−1), and outstanding durability (720 h at 10 mA cm−2). This work provides an innovative avenue to design high-performance heterojunction electrocatalysts for perdurable Zn-air batteries.

Structure-performance relations for carbons in Zn-air battery cathodes with non-alkaline electrolytes

Rechargeable Zn-air batteries (RZABs) with non-alkaline electrolytes are a promising type of energy storage devices that potentially combine low cost, high energy density and safety. However, cathode materials for these devices remain poorly developed. We present a systematic study of how structure of carbons affects their performance as cathode scaffolds in non-alkaline RZABs. Ten commercially available types of carbon are characterized and tested in Zn-air battery cathodes with 1 M Zn(OAc)2 or ZnSO4 solutions in H2O as electrolytes. At a low current density (0.1 mA cm−2), there is a roughly linear dependence between the roundtrip energy efficiency and the logarithm of BET surface area, and this dependence is relevant across materials with different morphology and graphitization degree. Lower overpotentials at the initial cycles are observed for cathodes that are more hydrophilic. At higher currents (1 mA cm−2), morphology plays an important role for oxygen reduction kinetics, with nanosized carbons having a much better performance compared to microporous materials with micron-sized particles. Overall, the best performance in non-alkaline RZABs is achieved for nanosized carbons with high specific surface area (>450 m2g− 1). Our findings help to formulate structural and morphological guidelines for choosing or synthesizing an optimal carbon scaffold for RZABs.

Boosting Urea Electrooxidation Activity of Ni5P4 by Vanadium Doping for Urea-Assisted Renewable Energy Conversion Devices

The urea oxidation reaction (UOR), a competitive substitute for the oxygen evolution reaction (OER), holds superior potential to meet the upsurge of renewable energy conversion due to low theoretical potential while the sluggish UOR kinetics impede its practical application. In this report, for the first time, we demonstrate that the UOR activity of Ni5P4 is improved via V incorporation. The novel amorphous V-doped Ni5P4 (V10%-Ni5P4) microflower structure with optimized electronic structure was prepared by a solvothermal–phosphorization process. With V atoms involved, the V10%-Ni5P4 microflowers are assembled by much thinner, denser nanosheet units compared with the Ni5P4 counterpart, which endows it with more active sites, enhanced mass transfer, conductivity, and better wettability. The V10%-Ni5P4 microflowers exhibit outstanding UOR activity of 282 mA cm–2 at 1.6 V vs RHE with a low Tafel slope (36.1 mV dec–1). Furthermore, the urea-assisted electrolytic cell only needs 1.44 V to provide 50 mA cm–2 and the urea-assisted rechargeable Zn-Air battery (uZAB) is illustrated to have a higher open-circuit voltage of 1.43 V and possesses a lower potential gap than that Pt/Ir-based uZABs. This report sheds light on the role of vanadium in crystallization and structure optimization and lays the foundation for developing new UOR electrocatalysts.

Metal-mediated Schiff base polymer enables metal/nitrogen codoped carbon nanosheets as efficient bifunctional electrocatalyst for durable rechargeable Zn-air batteries

We report a simple yet robust route to bifunctional electrocatalysts comprising FeNi and Co4N hybrid nanoparticles co-embedded within N-doped carbon nanosheets (denoted FeNi/Co4N-NCS) for rechargeable Zn-air batteries (ZABs) with high power density and capacity as well as outstanding cycling stability, markedly outperforming the Pt/C&IrO2 electrocatalyst counterpart. The as-crafted FeNi/Co4N-NCS electrocatalysts display outstanding bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity with a low overall oxygen electrode activity (ΔE = 0.664 V). Density functional theory (DFT) calculations reveal that the synergy of FeNi and Co4N reduces the rate-determining step (RDS) energy barrier, thereby greatly increasing electrocatalytic activity. The aqueous ZAB assembled with FeNi/Co4N-NCS delivers a high power density of 160 mW cm−2, large specific capacity of 812 mAh g−1Zn, and long cycling life of 1450 h at 5 mA cm−2. This study highlights an effective strategy to yield durable bifunctional electrocatalysts for metal-air batteries.

Electrocatalytic performance of Ni-promoted Co nanoclusters supported by N-doped carbon foams for rechargeable Zn-air batteries

Ni/Co diatomic clusters supported on nitrogen-doped carbon foams are prepared via molten salt method to improve the density of surface active sites of zinc-air battery catalysts and further explore metal-modified carbon-based catalysts. The influence of Co and Ni atoms on the carbon foam structure is investigated by X-ray diffraction and high-resolution electron microscopy, and the presence of metal atoms in N-doped carbon foams is confirmed by X-ray spectroscopy. The left shift of the diffraction peak of Co doped graphitic carbon indicates an increase in the interlayer spacing and a reduced graphitization degree, while the introducton of Ni atoms promotes graphitization. For Ni–Co/NFC-2, Ni inhibits the insertion of Co in carbon layer by increasing graphitization, thus exposing more Co-active substances on the surface, which is important for improving the catalytic process of ORR and OER. According to electrochemical tests, Ni–Co co-doped carbons exhibited superior bi-functional electrocatalytic performance with oxygen reduction reaction (ORR) Eonset = 0.97 V and a Tafel slope of 49.5 mV dec−1, accompanied by oxygen evolution reaction (OER) Ej = 10 mA cm−2 = 1.46 V. Zinc-air battery (ZAB) cell, utilizing the developed material as a catalyst, exhibited a high discharge power density of 138 mW cm−2 with stable performance for up to 200 h.

Atomically dispersed Fe-Ni dual sites in heteroatom doped carbon tyres for efficient oxygen electrocatalysis in rechargeable Zn-Air battery

The electronic and functional synergies between the twin metal centers make dual single-atom catalysts (DACs) attractive for oxygen electrocatalysis. The catalytic activities of DACs are largely decided by their surrounding micro-environment and supporting substrates. Modulating the micro-environment as well as engineering the efficient support is challenging tasks. Moreover, both are critical to optimizing the performance of DACs. Herein, a novel bio-cooperative strategy is developed to synthesize FeNi-DAC wherein Fe-Ni dual-atom sites are embedded in the N, P codoped tyre shaped carbon matrix. The configuration matching of Fe-Ni dual centers together with the local electronic engineering of N, P heteroatoms synergistically boost the catalytic activity on the oxygen reaction. Furthermore, the central-hollow highly-porous carbon matrix not only gives rise to a large amount of active sites, but also facilitates fast kinetics. Taking advantage of both the DAC and the substrate, the FeNi-NPC hollow tyre (HT) catalyst scores high in both oxygen reduction and evolution reactions, which exhibits the narrow potential difference and excellent durability. The aqueous Zn-air full battery (ZAB) integrating the FeNi-NPC HT air cathode has a high power density and a good stability over long-term cycling. Moreover, the flexible solid-state ZAB assembled with the polymer electrolyte obtains the high reliability over a wide range of temperatures or under diverse outside deformations. Therefore, this work offers a new green approach to prepare highly efficient DACs with built-in modulated micro-environment and tailor-made substrates. Moreover, it also paves a new way to develop highly-pliable power source for flexible electronics.

Corrosion-engineered stereoscopic nano-microflower FeOOH for efficient electrocatalysis toward oxygen evolution reaction

Designing inexpensive and high-efficiency Fe(oxy)-hydroxide nanomaterials are essential to accelerate the sluggish kinetics of oxygen evolution reaction (OER). However, it is still a challenge to increase its electronic conductivity and exposure of the active site, as well as make it work under high current densities. Herein, a facile corrosion engineering strategy is proposed to in-situ synthesize the self-supporting Fe(oxy)-hydroxide heterostructures on nickel foam substrate in the corrosion system of “FeCl3-NaCl”. The morphologies and phase compositions characterization show that Cl- concentration can accelerate the oxygen corrosion process, while the concentration and species of metal irons can change the composition of the corrosion products. The synergistic effect of Cl- and Fe3+ enabled the FeOOH-Fe2.0 catalyst with stereoscopic nano-microflower structure, which owns abundant active sites, strong catalyst-base bond interaction, and fast electron transfer efficiency, reducing the potential reaction barrier of OER kinetics. Therefore, the obtained FeOOH-Fe2.0 provides a lower overpotential of 263 mV to achieve the current density of 100 mA cm−2 and a low Tafel slope of 64.03 mV dec−1 in 1 M KOH electrolyte. Furthermore, the FeOOH-Fe2.0 catalyst is used as an air electrode material to assemble Zn-air battery, which reaches the peak power density of 107.10 mW cm−2 and achieves long-term charge/discharge performance. This project offers a simple and effective method for preparing high-efficiency OER catalyst by corrosion strategy and confirms its application prospect in rechargeable Zn-air batteries.

Zn/CoP polyhedron as electrocatalyst for water splitting and Zn-air battery

High efficient electrocatalytic activity towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are very critical to renewable energy technologies such as water splitting、rechargeable Zn-air battery. As a promising class of catalysts, the transition metal phosphide that are considered as promising substitutes to noble metal based catalysts. In this work, the N-doped polyhedral Zn/CoP porous material was obtained by high-temperature pyrolysis of Zn/ZIF67 as precursor. The optimized Zn/CoP sample possessed outstanding bifunctional activity of OER and HER in 1 M KOH, it also possesses HER activity in 0.5 M H2SO4. The Zn/CoP electrode with meso/macropores can act as both an anode and a cathode to fabricate an electrolyzer for overall water splitting, it was able to achieve a current density of 10 mA cm−2 at a cell voltage of 1.41 V with remarkable stability. Meanwhile, the corresponding rechargeable Zn-air battery based on Zn/CoP air cathode also exhibit an open circuit voltage of 1.43 V, low charge-discharge voltage gap (0.96), high power density (93.6 mW cm−2), and strong cycle stability, making it a suitable alternative to take the place of precious metal catalysts for practical utilization.

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

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

Controllable synthesis of Co/MnO heterointerfaces embedded in graphitic carbon for rechargeable Zn–air battery

Owing to the unique geometric and electronic structure, design and synthesis of electrocatalysts with well defined heterointerfaces are essential for clean energy technologies, for instance water-splitting and Zn-air batteries. Herein, a bifunctional electrocatalyst assembled by Co/MnO nanoparticles and nitrogen doping double-sphere carbon (denoted as Co/MnO@N-DSC), was fabricated via a solvothermal and pyrolysis strategy. The Co/MnO@N-DSC catalysts exhibit an enhanced bifunctional oxygen electrocatalytic performance for Oxygen reduction reaction (ORR) (E1/2, 0.84 V vs. RHE) and oxygen evolution reaction (OER) (Eonset, 1.54 V vs. RHE). As an air cathode catalyst, the Co/MnO@N-DSC-based Zn-air battery can afford prime performance, over the commercial noble-metal-based Zn-air battery. Theoretical calculation results indicate that the synergism of Co (111)/MnO (200) heterointerfaces can enhance charge transfer and provide extra electrons for the reaction processes. This work provides a promising manoeuvre to uplift bifunctional catalytic activity by increasing the synergy from heterointerfaces of transition-metal/metal oxide in oxygen electrocatalysis.

Three-dimensionally ordered Co3O4@WO3 composite arrays as a binder-free air cathode for high-performance Zn-air batteries

The development of low-cost, stable, and highly-active bifunctional catalysts is an important step to realize high-performance rechargeable Zn-air batteries. Herein, we report an innovative air cathode of three-dimensionally (3D) ordered macroporous Co3O4@WO3 composite arrays on a flexible carbon cloth substrate prepared by the decoration of Co3O4 nanosheets on electrodeposited macroporous WO3 inverse opals. Benefiting from a high specific surface area, rich active sites, and a facilitated charge/mass transfer process provided by the 3D ordered macroporous structure, the as-prepared Co3O4@WO3 composite exhibits excellent bifunctional catalytic activity with a half-wave potential of 0.75 V for oxygen reduction reaction and an overpotential of 339 mV at 10 mA/cm2 for oxygen evolution reaction, contributing to a low oxygen potential gap (ΔE) of 0.81 V. Furthermore, Co3O4@WO3 composite arrays are directly used as a binder-free air cathode for rechargeable Zn-air batteries, ensuring excellent mechanical and electrochemical stability. The aqueous Zn-air batteries based on 3D Co3O4@WO3 air cathodes exhibit excellent performance, in terms of a high specific capacity of 828.6 mAh/gZn1 at 5 mA/cm2 and long-term cycling stability of over 646 h.

3D Porous N and S Co-doped CNT Microspheres with Highly Dispersed CoP Nanoparticles: Toward an Efficient Bifunctional Electrocatalyst for Zn-Air Batteries

The design and efficient synthesis of oxygen redox electrocatalysts possessed with high activity are of the essence for advanced rechargeable Zn-air batteries (ZABs). In particular, porous architectures composed of transition metal compound and carbonaceous material have attracted significant attention owing to their enhanced electrocatalytic activity. This study reports the fabrication of metal-free N and S co-doped porous CNT microspheres (3DNSCNT) via spray drying and subsequent post-treatment. Moreover, to hybridize with metal phosphide, CoP nanoparticles are uniformly decorated on the microspheres (3DNSCNT/CoP) by the hydrothermal method and phosphidation treatment. Due to the effect of the combination of the porous architecture inside the entangled 3DNSCNT and uniformly deposited CoP nanoparticles, 3DNSCNT/CoP exhibits superior bifunctional electrocatalytic activities for oxygen redox reaction in 0.1 M KOH electrolyte compared with noble metal-based catalysts like Pt and Ru. Furthermore, as an air cathode for ZABs, 3DNSCNT/CoP exhibits a high-power density (177 mW cm-2), low polarization overpotential, and durable cycle performance (200 h).

Nitrogen-doped NiCo2O4 nanowires on carbon paper as a self-supported air cathode for rechargeable Zn-air batteries

A noble-metal-free bifunctional electrocatalyst with outstanding activity and stability is of great importance for the development of rechargeable zinc-air batteries (ZABs). Herein, we employed a facile strategy to fabricate nitrogen-doped NiCo2O4 nanostructures on carbon paper as a binder-free air cathode for rechargeable ZABs. An optimized process of nitrogen plasma treatment has enhanced the electrical conductivity of the metal oxide and induced abundant active sites into the crystal structures, resulting in enhanced electrocatalytic activities toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Notably, mild plasma treatment leads to efficient N doping while the morphology and specific surface area of the catalyst both remain unchanged. The air cathode with NiCo2O4 doped with nitrogen in 2 min plasma treatment and integrated into a zinc-air battery with liquid electrolyte provided a small charge-discharge voltage gap and distinguished cycling stability superior to the air cathode with noble-metal catalyst counterparts. Furthermore, the solid-state zinc-air battery with this material displays excellent stability with just a small increase of the charge-discharge voltage gap over 20 h of operation. This work illustrates the promising potential of plasma treatment in the fabrication of high-performance catalysts.

Hygroscopic and Malleable Dough‐Type Zn–Air Battery in a Dry Condition Utilizing Deliquescence

AbstractFlexible and rechargeable Zn–air batteries (ZAB) are promising candidates for attaining the high energy density required for next‐generation energy storage devices given their half‐open cathode configuration. However, the poor interfacial contact between the immobilized solid‐state electrolyte and porous cathode, and drying‐out of water in the electrolyte at low relative humidity (RH) of 30% or less, cause low performance and short lifespan. Herein, a novel hygroscopic dough‐type electrolyte with water‐absorbing and malleable free‐standing configuration originating from deliquescent KOH and severe gelation of sodium alginate (SA) by facile kneading is proposed. Because appropriate contents are required to absorb water from the atmosphere and obtain the manageable form of the dough used here, the materials composing the dough electrolyte, i.e., SA, water, and KOH, are precisely controlled to ensure high malleability, scalability, ionic conductivity, and good water retention capabilities. The optimized dough inhibits evaporation at low RH and lowers the interfacial resistance with the cathode via tight adhesion. The dough‐type ZABs show noteworthy maximum power density of 160 mW cm−2 with low catalyst mass loading (0.4 mg cm−2), specific capacity of 632 mAh gZn−1, and stability for 60 h at RH 30% and 120 h even at low temperature of −20 °C, producing reasonable output.

CoSe2 nanoparticles anchored on CoNC carbon nanoplates as bifunctional electrocatalyst for flexible rechargeable Zn-air batteries

A flexible solid rechargeable Zn-air battery for advanced energy conversion and storage has extensive applications in portable electric sources, wildlife rescue and flexible wearable systems. Herein, the CoSe2 nanoparticles anchored on cobalt-embedded N-doping carbon nanoplates (CoSe2/CoNC) is developed as a highly active bifunctional catalyst via pyrolysis and selenization of bimetallic zeolitic imidazolate frameworks containing Zn and Co. The introduction of inactive Zn generates strong electrochemically active surface areas due to the synergistic effect between CoSe2 nanoparticles and CoNC matrix. Further, CoSe2/CoNC exhibits prominent Zn–air battery performance and even outperforms the commercially available noble-metal catalysts. Notably, a high-rate flexible Zn-air battery enabled by an alkaline composite polyacrylic acid-carboxymethyl cellulose electrolyte delivers the open-circuit potential of 1.51 V. The battery offers high wearability and performs very well under various conditions, such as soaking, drilling and sewing.

Engineering Cost-Efficient CoS-Based Electrocatalysts for Rechargeable Zn-Air Battery Application

The development of low-cost and efficient electrocatalysts toward the oxygen evolution reaction (OER) is crucial for clean energy devices such as metal-air batteries and fuel cells. Herein, a novel CoS@FeOOH electrocatalyst is synthesized by in-situ deposition of FeOOH nanoparticles on metallic organic frame (MOF) derived CoS hollow polyhedrons. Due to the coupling synergetic effect of FeOOH and CoS, CoS@FeOOH presents an excellent OER catalytic performance with both high electrocatalytic activity and durable cycling stability, far superior to the pristine CoS and commercial RuO2 electrocatalysts. The assembled rechargeable zinc-air battery (ZAB) using CoS@FeOOH as the OER electrocatalyst shows a maximum power density of 89.1 mW cm–2 and continuously runs 60 h without evident polarization increment, which is far better than the ZAB using the commercial RuO2 OER electrocatalyst. The robust catalytic performance of the CoS@FeOOH electrocatalyst is mainly attributed to the regulated electronic configurations accelerating charge transfer, abundant oxygen vacancies promoting catalytic activity, and an FeOOH protection layer inhibiting active Co dissolution.