Zinc-air Research Articles

Meso/Microporous Single‐Atom Catalysts with Curved Fe‐N4 sites Boost the Oxygen Reduction Reaction Activity

Zeolitic‐imidazolate frameworks (ZIFs) are among the most efficient precursors for the synthesis of atomically dispersed Fe‐N/C materials, which are promising catalysts for enhancing the performance of Zn‐air batteries (ZABs) and proton exchange fuel cells (PEMFCs). However, existing ZIF‐derived Fe‐N/C electrocatalysts mostly consist of microporous materials, leading to insufficient mass transport and inadequate battery/cell performance. In this study, we synthesize an atomically dispersed meso/microporous Fe‐N/C material with curved Fe‐N4 active sites, denoted as FeSA‐N/TC, through the pyrolysis of hemin‐modified ZIF films on ZnO nanorods, obtained from the self‐assembly reaction between Zn2+ from ZnO hydrolysis and 2‐methylimidazole. Density functional theory calculations demonstrate that the curved Fe‐N4 active sites can weaken the intermediate adsorptions, resulting in lower free energy barriers and enhanced performance during oxygen reduction reaction (ORR). Specifically, FeSA‐N/TC exhibits exceptional ORR performance with half‐wave potentials of 0.925 V in alkaline media and 0.825 V in acidic media. When used as the cathodic catalyst in PEMFCs and ZABs, FeSA‐N/TC achieves high peak power densities (H2‐O2 PEMFC: 1100 mW cm–2; H2‐Air PEMFC: 715 mW cm–2; liquid‐state ZAB: 228 mW cm–2; solid‐state ZAB: 112 mW cm–2), demonstrating its feasibility and efficiency in practical applications.

Meso/Microporous Single-Atom Catalysts with Curved Fe-N4 sites Boost the Oxygen Reduction Reaction Activity.

Zeolitic-imidazolate frameworks (ZIFs) are among the most efficient precursors for the synthesis of atomically dispersed Fe-N/C materials, which are promising catalysts for enhancing the performance of Zn-air batteries (ZABs) and proton exchange fuel cells (PEMFCs). However, existing ZIF-derived Fe-N/C electrocatalysts mostly consist of microporous materials, leading to insufficient mass transport and inadequate battery/cell performance. In this study, we synthesize an atomically dispersed meso/microporous Fe-N/C material with curved Fe-N4 active sites, denoted as FeSA-N/TC, through the pyrolysis of hemin-modified ZIF films on ZnO nanorods, obtained from the self-assembly reaction between Zn2+ from ZnO hydrolysis and 2-methylimidazole. Density functional theory calculations demonstrate that the curved Fe-N4 active sites can weaken the intermediate adsorptions, resulting in lower free energy barriers and enhanced performance during oxygen reduction reaction (ORR). Specifically, FeSA-N/TC exhibits exceptional ORR performance with half-wave potentials of 0.925 V in alkaline media and 0.825 V in acidic media. When used as the cathodic catalyst in PEMFCs and ZABs, FeSA-N/TC achieves high peak power densities (H2-O2 PEMFC: 1100 mW cm-2; H2-Air PEMFC: 715 mW cm-2; liquid-state ZAB: 228 mW cm-2; solid-state ZAB: 112 mW cm-2), demonstrating its feasibility and efficiency in practical applications.

High-Entropy Ag-Ru-Based Electrocatalysts with Dual-Active-Center for Highly Stable Ultra-Low-Temperature Zinc-Air Batteries.

The development of advanced bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is significant for rechargeable zinc-air batteries (ZABs). Herein, a unique dual active center alloying strategy is proposed to achieve the efficient bifunctional oxygen catalysis, and the high entropy effect is further exploited to modulate the structure and performance of the catalysts. The MOF-assisted pyrolysis-replacement-alloying method was employed to construct the CoCuFeAgRu high-entropy alloy (HEA), which are uniformly anchored in porous nitrogen-doped carbon nanosheets. Notably, the obtained HEA catalyst exhibits excellent catalytic performance for both ORR and OER, and a peak power density of 136. 53 mW cm-2 and an energy density of 987.9 mAh gZn -1, surpassing the most of the previously reported bifunctional oxygen electrocatalysts. Moreover, the assembled flexible rechargeable ZAB enables excellent performance even at the ultralow temperature of -40 °C, with an energy density of 601.6 mAh gZn -1 and remarkable cycling stability up to 1,650 hours. Combined experimental and theoretical calculation results reveal that the excellent bifunctional catalytic activity of the HEA catalyst originated from the synergistic effect of the Ag and Ru dual active centers, and the optimization of the electronic structure by alloying effect.

High‐Entropy Ag‐Ru‐based Electrocatalysts with Dual‐Active‐Center for Highly Stable Ultra‐Low‐Temperature Zinc‐Air Batteries

The development of advanced bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is significant for rechargeable zinc‐air batteries (ZABs). Herein, a unique dual active center alloying strategy is proposed to achieve the efficient bifunctional oxygen catalysis, and the high entropy effect is further exploited to modulate the structure and performance of the catalysts. The MOF‐assisted pyrolysis‐replacement‐alloying method was employed to construct the CoCuFeAgRu high‐entropy alloy (HEA), which are uniformly anchored in porous nitrogen‐doped carbon nanosheets. Notably, the obtained HEA catalyst exhibits excellent catalytic performance for both ORR and OER, and a peak power density of 136. 53 mW cm‐2 and an energy density of 987.9 mAh gZn‐1, surpassing the most of the previously reported bifunctional oxygen electrocatalysts. Moreover, the assembled flexible rechargeable ZAB enables excellent performance even at the ultralow temperature of ‐40°C, with an energy density of 601.6 mAh gZn‐1 and remarkable cycling stability up to 1,650 hours. Combined experimental and theoretical calculation results reveal that the excellent bifunctional catalytic activity of the HEA catalyst originated from the synergistic effect of the Ag and Ru dual active centers, and the optimization of the electronic structure by alloying effect.

All-in-One Polymer Gel Electrolyte towards High-Efficiency and Stable Fiber Zinc-Air Battery.

Fiber zinc-air batteries are explored as promising power systems for wearable and portable electronic devices due to their intrinsic safety and the use of ambient oxygen as cathode material. However, challenges such as limited zinc anode reversibility and sluggish cathode reaction kinetics result in poor cycling stability and low energy efficiency. To address these challenges, we design a polydopamine-based all-in-one gel electrolyte (PAGE) that simultaneously regulates the reversibility of zinc anodes and the kinetics of air cathodes through polydopamine interfacial and redox chemistry, respectively. The intrinsic catechol and carboxylate groups in PAGE regulate the transport and solvation structure of Zn2+, facilitating dendrite-free zinc deposition with a lamellar stacking morphology. Additionally, the oxidation of redox-active catechol groups in PAGE replaces the sluggish oxygen evolution reaction on the air cathode and reduces the energy barrier for charging, enabling fiber zinc-air batteries to achieve a significantly improved energy efficiency of 95% and a longer lifespan of 40 hours. Further integration into self-powered electronic textiles underscores its potential for next-generation wearable systems.

Enhancing the hole utilization efficiency of Ti–Fe2O3 photoelectrode by decorating CoCu-ZIF for efficient photo-assisted rechargeable zinc air batteries

To enhance the oxygen evolution reaction (OER) performance of the zinc-air battery (ZAB), reduce charging voltage, and improve energy utilization efficiency, a sunlight-assisted strategy has been implemented. The photo-assisted rechargeable ZAB was proposed, featuring Ti–Fe2O3 decorated with Co0·8Cu0.2-ZIF as the air electrode. Upon illumination, valence band holes were generated in Ti–Fe2O3, oxidizing Co2+ in Co0·.8Cu0.2-ZIF to Co3+/Co4+, enhancing OER performance, reducing the charging voltage from 2 V to 1.3 V and effectively narrowing the charging-discharging voltage gap from approximately 1.15 V–0.45 V. The Ti–Fe2O3/Co0·8Cu0.2-ZIF structure maintains a round-trip efficiency of 65.3% after 300 cycles. This result demonstrates the successful integration of photoelectrochemical principles with ZAB technology, showcasing its efficacy in solar energy storage and light energy conversion.

Recent Achievements in Heterogeneous Bimetallic Atomically Dispersed Catalysts for Zn-Air Batteries: A Minireview.

Rechargeable Zn-air batteries (ZABs) hold promise as the next-generation energy-storage devices owing to their affordability, environmental friendliness, and safety. However, cathodic catalysts are easily inactivated in prolonged redox potential environments, resulting in inadequate energy efficiency and poor cycle stability. To address these challenges, anodic active sites require multiple-atom combinations, that is, ensembles of metals. Heterogeneous bimetallic atomically dispersed catalysts (HBADCs), consisting of heterogeneous isolated single atoms and atomic pairs, are expected to synergistically boost the cyclic oxygen reduction and evolution reactions of ZABs owing to their tuneable microenvironments. This minireview revisits recent achievements in HBADCs for ZABs. Coordination environment engineering and catalytic substrate structure optimization strategies are summarized to predict the innovation direction for HBADCs in ZAB performance enhancement. These HBADCs are divided into ferrous and nonferrous dual sites with unique microenvironments, including synergistic effects, ion modulation, electronic coupling, and catalytic activity. Finally, conclusions and perspectives relating to future challenges and potential opportunities are provided to optimise the performance of ZABs.

High activity of cobalt-atomically dispersed catalyst on mesoporous carbon for rechargeable Zn-air batteries via effective removal of the hard template

The use of oxygen from air in Zn-air batteries requires the smart design of materials with bifunctional activity for oxygen reduction and evolution reactions (ORR/OER), and with a porous structure to facilitate the diffusion of oxygen gas to active sites. Kit-6 template-assisted porous structures have been proposed to this end; however, traditional methods for the removal of Kit-6 templates are highly aggressive and environmentally harmful. In this study, we present the synthesis of a cobalt atomically dispersed catalyst (Co-ADC) with interlayer engineering using mesoporous Kit−6 templates, focusing on two removal strategies: sodium hydroxide (0.5, 1, and 2 M) and hydrofluoric acid (15, 30, and 45 %). Physicochemical results indicated that Co-ADC-containing nanoparticles were obtained using the proposed methodology, while the use of HF promoted the loss of cobalt in the catalyst. During the activity evaluation for the ORR, and it was found that 0.5 M NaOH and HF at 15 % displayed similar activity, which could be related to the effect of carbon material as co-catalyst, but the first enabled a close 4e− pathway, and thus, the Co-ADC presented a ΔEOER-ORR of 640 mV. This optimized ADC displayed improved functionality owing to diffusion improvements by the mesoporous structure, presenting a maximum power density of 130.6 mW cm−2 and 30 % higher specific activity than the Pt + IrO2/C reference material. Rechargeability was evaluated, yielding a ΔV = 0.87 V at 5.175 mA cm−2 with a round-trip efficiency of 57.5 %. Nonetheless, the optimized material presented higher rechargeability, displaying no significant round-trip changes after 100 cycles, while Pt + IrO2/C presented changes due to OER issues after only 48 cycles.

Joule heating synthesis for single-atomic Fe sites on porous carbon spheres and armchair-type edge defect engineering dominated oxygen reduction reaction performance

Single-atom catalysts (SACs) embedded in heteroatom-doped carbon are the most promising oxygen reduction reaction (ORR) electrocatalysts. However, the expeditious and facile synthesis of high-performance SACs with Fe-Nx active sites and identifying the role of edge-type defect at the atomic level in carbon support are essential but remain challenging. Herein, Joule heating is applied to anchor Fe single atoms on newly defect rich porous carbon spheres (Fe-N-DCSs) in milliseconds. Fe-N-DCSs achieves exceptional ORR performance, with a half-wave potential (E1/2) of 0.90 V and E1/2 lost of only 20 mV after 30,000 cycles in 0.1 M KOH, and superior Zn-air batteries performances. Density functional theory calculations establish that armchair-type edge defects decorated Fe-N4 active sites boost the desorption of OH* and diminish the ORR overpotential. This work not only provides a speedy route for the fabrication of SACs but also presents new insights into the excellent ORR activity.

Carbothermal Reduction-Assisted Synthesis of a Carbon-Supported Highly Dispersed PtSn Nanoalloy for the Oxygen Reduction Reaction.

Exploring high-performance and low-platinum-based electrocatalysts to accelerate the oxygen reduction reaction (ORR) at the air cathode of zinc-air batteries remains crucial. Herein, by combining electroless deposition and carbothermal reduction, a nitrogen-doped carbon-supported highly dispersed PtSn alloy nanocatalyst (PtSn/NC) was prepared for a high-efficiency ORR process. Electrochemical measurements show that PtSn/NC exhibits excellent electrocatalytic ORR activity with a half-wave potential of 0.850 V versus reversible hydrogen electrode (RHE), which is higher than that of commercial Pt/C (0.815 V). The PtSn/NC-based (20 μgPt cm-2) rechargeable Zn-air battery exhibited astonishing performance with a maximum power density of up to 150.1 mW cm-2, as well as excellent rate performance and charge/discharge stability. Physical characterization reveals that carbothermal reduction could compel the transformation of Sn oxide into metallic Sn, which then alloys with the deposited Pt atoms to form the PtSn nanoalloy, in which electrons are transferred from Sn atoms to neighboring Pt atoms, thereby improving the ability of Pt-based active sites to catalyze the ORR process in PtSn/NC by optimizing the unoccupied d-band of Pt atoms. This work provides a reliable and innovative route for the rational design of highly dispersed Pt-based alloy ORR electrocatalysts.

Lignin-derived Fe–N–C electrocatalyst with 3D porous structure for efficient oxygen reduction reaction

Developing low-cost, high-performance oxygen reduction reaction (ORR) catalysts is crucial for the commercialization of fuel cells and zinc-air batteries. Herein, we report a lignin-derived Fe/N co-doped 3D porous carbon electrocatalyst Fe-NLC-1 as an alternative to commercial Pt/C catalysts, which was synthesized by a green and facile in situ carbonization strategy. Fe-NLC-1 exhibits higher oxygen reduction activity with a half-wave potential (E1/2) of 0.90 V vs. RHE than commercial 20 wt% Pt/C (E1/2 = 0.85 V) in the alkaline conditions, as well as excellent methanol tolerance and stability. Furthermore, the Zn-air battery loaded with Fe-NLC-1 exhibits a maximum power density of 125 mW cm−2, an open circuit voltage of 1.477 V, and stable discharge performance, which are comparable or even better than the commercial Pt/C. This study highlights the potential of biomass-derived porous carbon materials for the development of high-performance ORR electrocatalysts.

MnO2/rGO bifunctional catalyst and support materials for gel polymer electrolyte based Zn-air batteries

A high-performance and long-lasting, rechargeable Zn-air battery requires a reliable and effective bifunctional catalyst material to facilitate the oxygen reduction and oxygen evolution reactions during the battery operation. Manganese oxide (MnO2) is a promising non-precious perspective due to its multivalency and various polymorphic structures that effectively catalyze oxygen evolution and reduction. In the present work, MnO2 nanowires (NWs) have been integrated with over-reduced graphene oxide (rGO) in various concentrations via a facile hydrothermal route. The synthesized materials, tested in lab-made zinc-air battery devices fabricated using gel polymer electrolyte, exhibit a significant enhancement in the performance and 2–3 times the cycle life compared to the bare MnO2. The ZAB device was tested for galvanostatic charge-discharge technique, and results exhibit a cycle life of 165 h (495 cycles@20 min per cycle) when discharged up to 1.0 V at a current density of 5.2 mA/cm2 and displayed a capacity of 731 mAh/gZn. Reduced graphene oxide acts as a support material that enhances the conductivity and surface area of the active material and also provides active sites for catalysis. This work signifies the importance of the engineering of the catalyst, support material, and additives, as slight changes may result in a significant enhancement in the cycle life.The appropriate composition of catalyst and support material and a compatible gel polymer electrolyte facilitates the fabrication of flexible zinc-air batteries for various applications.

High-performance rechargeable zinc-air batteries enabled by cobalt iron anchored on nitrogen-doped carbon matrix as bifunctional electrocatalyst

Developing efficient bifunctional oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) electrocatalysts is potential ways for achieving high rechargeable zinc-air (Zn-air) battery performance. Herein, we report an iron (II) acetate-assisted strategy to synthesize Co3Fe7-NC-OAc catalyst with cobalt iron (Co3Fe7) alloy anchored on nitrogen-doped carbon (NC) matrix, which can serve as efficient ORR/OER bifunctional electrocatalysts for rechargeable Zn-air batteries. Apart from alloying with Co to form ORR/OER active Co3Fe7 nanoparticles, the incorporation of iron (II) acetate has expanded the pore size inside the Co3Fe7-NC-OAc catalyst to serve as gas transfer channels, and has induced synergetic electronic coupling between Co3Fe7 nanoparticles and NC matrix for boosting catalytic activity. Therefore, Co3Fe7-NC-OAc exhibits favorable ORR activity with a most positive half-wave potential of 0.90 V vs. RHE, fast ORR kinetics with a highest kinetic current density of 57.4 mA cm−2 at 0.85 V vs. RHE, and fast O2 diffusion and transport that enables smaller mass transport overpotential at high current density up to 800 mA cm−2. Additionally, Co3Fe7-NC-OAc can catalyze OER with low overpotential of 310 mV at 10 mA cm−2. When employed as air electrode for Zn-air batteries, Co3Fe7-NC-OAc achieve high peak power densities of 193 mW cm−2 and 587 mW cm−2 in liquid and solid-state Zn-air batteries. The liquid battery also exhibits high specific capacity and remarkable cycling performance. This work opens up a new opportunity for developing highly efficient bifunctional electrocatalysts for Zn-air battery applications.

Nitrogen-doped carbon embedded with heterostructured Co3Fe7-Co5.47N nanoalloys for electrocatalytic oxygen reduction reaction in zinc-air battery

The oxygen reduction reaction (ORR) is the cathodic process in zinc-air batteries, but its sluggish kinetics significantly limit the energy conversion efficiency of these batteries. Therefore, developing high-performance ORR electrocatalysts is essential to support the advancement of zinc-air battery technology. Herein, a nitrogen-doped carbon embedded with heterostructured Co3Fe7-Co5.47N nanoalloys (FeCo@NC-900) was fabricated, and its electrocatalytic ORR activity and stability of FeCo@NC-900 were investigated in alkaline media. The FeCo@NC-900 catalyst exhibited a half-wave potential of 0.84 V, a Tafel slope of 76.06 mV·dec−1, and an electron transfer number (n) of approximately 3.83 for ORR. A rechargeable zinc-air battery was assembled using FeCo@NC-900 as the air cathode, achieving an open-circuit voltage of 1.435 V and a maximum power density of 81 mW cm−2, along with good cycling stability.

Advancements in Rechargeable Zn-Air Batteries with Transition-Metal Dichalcogenides as Bifunctional Electrocatalyst.

This review covers recent progress on transition metal dichalcogenides (TMDs) as bifunctional electrocatalysts for Zinc-air batteries (ZABs), emphasizing their suitable surface area, electrocatalytic active sites, stability in acidic/basic environments, and tunable electronic properties. It discusses strategies like defect engineering, doping, interface, and structural modifications of TMDs nanostructures for enhancing the performances of ZABs. Zinc-air batteries are promising energy storage devices owing to their high energy density, low cost, and environmental friendliness. However, the development of durable and efficient bifunctional electrocatalysts is a major concern for Zn-air batteries. In this review, we summarize the recent progress on transition metal dichalcogenides (TMDs) as bifunctional electrocatalysts for Zn-air batteries. We discuss the advantages of TMDs, such as high activity, good stability, and tunable electronic structure, as well as the challenges, such as low conductivity, poor durability, and limited active sites. We also highlight the strategies for fine-tuning the properties of TMDs, such as defect engineering, doping, hybridization, and structural engineering, to enhance their catalytic performance and stability. We provide a comprehensive and in-depth analysis of the applications of TMDs in Zn-air batteries, demonstrating their potential as low-cost, abundant, and environmentally friendly alternatives to noble metal catalysts. We also suggest future directions like exploring new TMDs materials and compositions, developing novel synthesis and modification techniques, investigating the interfacial interactions and charge transfer processes, and integrating TMDs with other functional materials. This review aims to illuminate the path forward for the development of efficient and durable Zn-air batteries, aligning with the broader objectives of sustainable energy solutions.

Defective wood-based chainmail electrocatalysts boost performances of seawater-medium Zn-air batteries

A high-activity and stable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalyst is critical for seawater-based Zn-air batteries (ZABs). Herein, we report a wood-derived chainmail electrocatalyst containing defective nitrogen-doped carbon nanotubes encapsulating cobalt nanoparticles (Co@D-NCNT/CW) to enhance the ORR/OER activity and stability in seawater medium. During the preparation process, the introduction and removal of Zn increased the defect sites and pyridine N content in the carbon material, modulating charge distribution and influencing the adsorption and activation processes. The highly ordered open channels in Co@D-NCNT/CW promoted mass transfer of reactants and accelerated gas diffusion. The resultant chainmail electrocatalyst exhibited impressive bifunctional ORR and OER activities with an ultra-low gap of 0.67 V in seawater-based alkaline electrolyte. The Co@D-NCNT/CW-assembled seawater-based rechargeable liquid ZABs demonstrated a maximum power density of 245.3 mW cm−2 and a long-term cycling performance over 500 h. The seawater-based all-solid-state ZABs achieved the maximum power density of 48.2 mW cm−2 and stabilized over 30 h. Density functional theory revealed that the presence of defects and pyridine nitrogen in Co@D-NCNT/CW modulated the electronic structure of Co, optimizing the binding affinity of the Co sites with intermediates and weakening Cl− adsorption. This work provides a new approach to preparing high-activity and stable ORR/OER electrocatalyst utilizing wood nanostructures, boosting the development of seawater-based ZABs.

Co/CoTe heterostructure internal hairy fibers as high-efficiency oxygen electrocatalyst for Zn-air batteries

The design of highly efficient catalysts to enhance the kinetics of oxygen reduction (OER) and oxygen evolution (ORR) reactions is the key issue for the development of high-performance Zn-air battery. In this work, we report the design of Co-CoTe heterostructured fibers as the bifunctional oxygen catalyst for Zn-air battery. Firstly, the theoretical analysis was carried out on Co-CoTe heterostructure. The large work function difference is favorable to construct strong interfacial built-in electric field (BIEF), and the low energy barrier endows high catalytic activities. Moreover, the in-situ grown carbon shell was designed to build “core–shell” Co-CoTe/C unit to realize its high performance. They assemble the Co-CoTe@HFS fiber with good self-supporting and flexible features. Taken the advantages of the strong BIEF, the “core–shell” basic unit, and the freestanding substrate, the Co-CoTe@HFS fiber achieves the good electrocatalytic properties and high reliability. The full Zn-air battery (ZAB) with the Co/CoTe@HFS air cathode achieves the high peak power density and cycling stability over long-term cycling. Therefore, this work provides a clue to design bifunctional oxygen catalysts for high-performance ZABs.

Highly asymmetrically configured single atoms anchored on flame-roasting deposited carbon black as cathode catalysts for ultrahigh power density Zn-air batteries

Iron group element-based single atom (SA) catalysts are highly regarded as promising alternatives to commercial Pt/C for catalysis of oxygen reduction reaction (ORR). For applications in rechargeable zinc-air batteries (ZABs), achieving the necessary high catalytic efficiency of the SAs toward oxygen evolution reaction (OER) however remains a significant challenge. Here, highly asymmetrically configured Fe SAs created with N,S co-coordination and anchored on flame-roasting deposited carbon black (CB), Fe-N3S1/CB, are developed, achieving outstanding bifunctional oxygen catalytic efficiency, with an ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10), outperforming the (Pt/C+RuO2) composite catalyst (0.697 V). With a newly proposed binder-free composite air cathode design, the Fe-N3S1/CB based ZAB achieves an ultrahigh power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2, largely outperforming the (Pt/C+RuO2) based ZAB (225.9 mW cm-2 at 344.7 mA cm-2). Furthermore, the Fe-N3S1/CB based ZAB demonstrates excellent long-term stability, with only 8.2% decay in round-trip efficiency over 1000 (333.3 h) charge-discharge cycles at 10 mA cm-2. Density functional theory calculations elucidate that incorporation of sulfur into the coordination sphere of Fe facilitates the electrochemical dehydroxylation step for ORR and accelerates the electrochemical O2 desorption step for OER, thereby reducing the corresponding free energy differences on Fe SAs for largely enhanced catalytic efficiency.1. A large size hetero-atom element, sulfur, is introduced to create highly asymmetrically configured Fe single atoms for enhancements in catalytic efficiency toward both oxygen reduction reaction and oxygen evolution reaction, and a binder-free composite air cathode design is proposed to improve electrochemical performances of zinc-air batteries.2. An ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10) is achieved for the air cathode, and an ultrahigh discharge power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2 is acquired for the zinc-air battery.

S-N co-doped porous carbon as metal-free ORR electrocatalysts in zinc-air batteries

The implementation of zinc-air batteries (ZABs) requires the creation of economically feasible electrocatalysts for the oxygen reduction reaction (ORR) process. In this work, sulfur-nitrogen co-doped porous carbon materials (S-N-PC) were synthesized using a straightforward approach including ball milling followed by calcination without solvent. The optimized S-N-PC 1000 demonstrates exceptional ORR performance in 0.1 M KOH, with a half-wave potential of 0.870 V that outperforms commercial Pt/C. Furthermore, it exhibits remarkable durability and exceptional methanol resistance. The S-N-PC 1000 performs excellent performance as an air cathode in ZABs, exhibiting a peak power density of 159.26 mW cm−2 and outstanding stability for up to 720 h. Additionally, the energy efficiency decreases by only 2.52 % after undergoing more than 2000 cycles of charging and discharging at 5 mA cm−2. This study offers a novel concept for the development of eco-friendly porous carbon catalysts for ZABs.

Enhanced Zinc-air battery performance and local electrochemical evaluation of atomically dispersed Co and Ni in S, N-codoped carbon nanofibers via scanning electrochemical microscopy

This study reports the successful synthesis of a novel electrocatalyst for oxygen reduction reactions (ORR), comprising S,N dual-doped carbon nanofibers with atomically dispersed Co/Ni species (denoted as Co,Ni-SAs/S,N-CNFs), leveraging electrostatic spinning to achieve a unique spatial architecture that maximizes both active site density and mass transport efficiency. Density functional theory (DFT) analysis identified the initial proton-electron transfer to adsorbed O2 as the rate-limiting step, with CoN3S1-NiN3S1 emerging as the pivotal active site structure catalyzing this critical reaction. The fabricated Co,Ni-SAs/S,N-CNFs electrocatalyst exhibited remarkable ORR performance, characterized by a high half-wave potential of 0.84 V and a low Tafel slope of 57.9 mV dec-1. To gain a comprehensive understanding of its catalytic behavior, a tailored temperature-controlled scanning electrochemical microscopy (SECM) was employed, enabling the mapping of reactivity distribution under simulated operating conditions while preserving structural integrity. Liquid zinc-air batteries (ZABs) with this electrocatalyst excelled, reaching 175 mW/cm2 power density and enduring 1240 cycles. The electrospun membrane catalyst enabled both button and flexible ZABs, adaptable to diverse environments. This study advances non-precious metal electrocatalyst design and offers insights for ZAB applications, fostering green energy prospects.