Oxygen Reduction Reaction Half-wave Potential Research Articles

FeN4S1 Single-Atom Sites Anchored on Three-Dimensional Porous Carbon for Highly Efficient and Durable Oxygen Electrocatalysis.

Precisely designing asymmetric active centers and exploring their electronic regulation effects to prepare efficient bifunctional single-atom catalysts (SACs) is important for boosting the practical applications of zinc-air batteries (ZABs). Herein, an effective strategy has been developed by introducing an axial S atom to the FeN4 active center, simultaneously assisted by pyrolyzing the graphene oxide (GO) sheathed zeolitic-imidazolate framework-8 (ZIF8) composite and constructing a three-dimensional (3D) porous framework with abundant FeN4S1 moieties. This structure can accelerate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics owing to the modulated electronic redistribution and d-band center with a reduced energy barrier. The optimal S-Fe-NC/rGO showcases a lower voltage gap (ΔE) of 0.64 V between both the ORR and OER half-wave potentials at 10 mA cm-2, highlighting the excellent bifunctional activities. The assembled S-Fe-NC/rGO rechargeable liquid ZABs deliver a power density of 154.05 mW·cm-2 and a desirable durability of >900 h. More importantly, the corresponding flexible solid-state ZABs exhibit considerable foldability.

Customized Heteronuclear Dual Single-Atom and Cluster Assemblies via D-Band Orchestration for Oxygen Reduction Reaction.

Advanced oxygen reduction reaction (ORR) catalysts, integrating with well-dispersed single atom (SA) and atomic cluster (AC) sites, showcase potential in bolstering catalytic activity. However, the precise structural modulation and in-depth investigation of their catalytic mechanisms pose ongoing challenges. Herein, a proactive cluster lockdown strategy is introduced, relying on the confinement of trinuclear clusters with metal atom exchange in the covalent organic polymers, enabling the targeted synthesis of a series of multicomponent ensembles featuring FeCo (Fe or Co) dual-single-atom (DSA) and atomic cluster (AC) configurations (FeCo-DSA/AC) via thermal pyrolysis. The designed FeCo-DSA/AC surpasses Fe- and Co-derived counterparts by 18 mV and 49 mV in ORR half-wave potential, whilst exhibiting exemplary performance in Zn-air batteries. Comprehensive analysis and theoretical simulation elucidate the enhanced activity stems from adeptly orchestrating dz 2-dxz and O 2p orbital hybridization proximate to the Fermi level, fine-tuning the antibonding states to expedite OH* desorption and OOH* formation, thereby augmenting catalytic activity. This work elucidates the synergistic potentiation of active sites in hybrid electrocatalysts, pioneering innovative targeted design strategies for single-atom-cluster electrocatalysts.

RETRACTED: Fe–Co co-doped 1D@2D carbon-based composite as an efficient catalyst for Zn-air batteries

A Fe-Co dual-metal co-doped nitrogen-containing carbon composite (FeCo-HNC) was prepared by adjusting the ratio of iron to cobalt as well as the pyrolysis temperature with the assistance of functionalized silica template. Fe1Co-HNC, which was made from 1D carbon nanotubes and 2D carbon nanosheets with a rich mesoporous structure, presented exceptional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activity. The ORR half-wave potential is 0.86 V (vs. reversible hydrogen electrode, RHE), and the OER overpotential is 0.76 V at 10 mA cm−2 with the Fe1Co-HNC catalyst, which can be applied to zinc-air batteries with superior performance. It is worth noting that the zinc-air batteries with Fe1Co-HNC-1000 as the cathodic catalyst achieved the highest power density of 94.9 mW cm−2 under a current density of 159.8 mA cm−2. This method provides a promising strategy for fabricating efficient transition metal-based carbon catalysts.

Directional Construction of Low-Coordination Fe-N3 Coupled with Intrinsic Carbon Defects for High-Efficiency Oxygen Reduction.

Regulating the coordination environment of Fe-Nx sites is an efficient but challenging approach for promoting the intrinsic catalytic activity of single-atom Fe/N-codoped carbon (Fe-N-C) toward the oxygen reduction reaction (ORR). Herein, low-coordination Fe-N3 sites coupled with carbon vacancies (Fe-N3/CV) are directionally constructed in Fe-N-C via pyrolysis of a metal-organic framework (MOF) precursor with N3-Zn-O-Fe moieties, which are delicately prefabricated by chemically anchoring Fe3+ onto a H2O-etching induced linker-missing Zn-N3 site in the MOF precursor. The optimized Fe-N-C with the Fe-N3/CV sites displays a high ORR half-wave potential of 0.92 V (vs RHE), which is attributed to the optimized electronic structure and binding strengths of the active Fe center toward the ORR intermediates stemming from the synergy of the asymmetric configuration of Fe-N3 as well as the adjacent carbon vacancies. This work could be enlightening for the design and construction of high-activity coupling sites in metal and nitrogen-codoped carbon catalysts.

Single atomic Fe-dispersed hollow carbon spheres coated with Co3O4 synergistically catalyze oxygen reduction and oxygen evolution reactions

It is highly expected to construct an efficient electrocatalyst having dual active sites that can simultaneously catalyze both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Zn-air batteries (ZABs). In this study, a new core-shell nanostructure (Co3O4/Fe-N4/HCS) consisting of single atomic Fe (Fe-N4)-dispersed hollow carbon spheres (Fe-N4/HCS) coated with Co3O4 nanoparticles (NPs) were successfully synthesized with SiO2 templates by a coating-polymerization-etching preparation strategy. Benefit from a synergistic effect of Co3O4 and Fe-N4 dual active species with unique HCS structure, Co3O4/Fe-N4/HCS displayed outstanding activity in both ORR (half-wave potential = 0.88 V) and OER (overpotential at 10 mA cm−2 = 0.33 V), respectively. Meanwhile, compared to Co3O4/Fe-N4/C with Co3O4 NPs on Fe-N4/C, Co3O4/Fe-N4/HCS with Co3O4 NPs on Fe-N4/HCS exhibits a higher stability during electrochemical processes depending on the stronger interaction between the Co3O4 NPs and atomic dispersed Fe-N4 sites embedded in unique HCS structure. Particularly, the ZABs fabricated by Co3O4/Fe-N4/HCS demonstrates a higher specific capacity (688.7 mAh gZn−1) and superior cycling durability over 80 h. The presence of the electron transfer from Co3O4 to Fe-N4 in Co3O4/Fe-N4/HCS, enables Fe-N4 bonded carbon electron deficiency. This promotes the deposition of Co3O4 NPs and enhances metal-HCS support interactions, which combined with a protecting effect of hollow carbon spherical shell on Co3O4 NPs inside the shell, achieving excellent catalytic stability. This research introduces a novel approach to design dual active sites as high-performance bifunctional ORR/OER catalysts.

Graphdiyne-Induced CoN/CoS2 Heterojunction: Boosting Efficiency for Bifunctional Oxygen Electrochemistry in Zinc-Air Batteries.

The performance of zinc-air battery is constrained by the sluggish rate of oxygen electrode reaction, particularly under high current discharge conditions where the kinetic process of the oxygen reduction reaction (ORR) decelerates significantly. To address this challenge, we present a novel phase transition strategy that facilitates the creation of a heteroatom-doped heterointerface (CoN/CoS2). The meticulously engineered CoN/CoS2/NC electrocatalyst displays a superior ORR half-wave potential of 0.87 V and an OER overpotential of 320 mV at 10 mA cm-2. Experimental and computational analysis confirm that the CoN/CoS2 heterostructure optimizes local charge distribution, accelerates electron transfer, and tunes active sites for enhanced catalysis. Notably, this heterojunction improves stability by resisting corrosion and degradation under harsh alkaline conditions, thus demonstrating superior performance and longevity in a custom-made liquid zinc-air battery. This research provides valuable practical and theoretical foundations for designing efficient heterointerfaces in electrocatalysis applications.

Constructing Co4(SO4)4 Clusters within Metal-Organic Frameworks for Efficient Oxygen Electrocatalysis.

Multinuclear metal clusters are ideal candidates to catalyze small molecule activation reactions involving the transfer of multiple electrons. However, synthesizing active metal clusters is a big challenge. Herein, on constructing an unparalleled Co4(SO4)4 cluster within porphyrin-based metal-organic frameworks (MOFs) and the electrocatalytic features of such Co4(SO4)4 clusters for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is reported. The reaction of CoII sulfate and metal complexes of tetrakis(4-pyridyl)porphyrin under solvothermal conditions afforded Co4-M-MOFs (M═Co, Cu, and Zn). Crystallographic studies revealed that these Co4-M-MOFs have the same framework structure, having the Co4(SO4)4 clusters connected by metalloporphyrin units through Co─Npyridyl bonds. In the Co4(SO4)4 cluster, the four CoII ions are chemically and symmetrically equivalent and are each coordinated with four sulfate O atoms to give a distorted cube-like structure. Electrocatalytic studies showed that these Co4-M-MOFs are all active for electrocatalytic OER and ORR. Importantly, by regulating the activity of the metalloporphyrin units, it is confirmed that the Co4(SO4)4 cluster is active for oxygen electrocatalysis. With the use of Co porphyrins as connecting units, Co4-Co-MOF displays the highest electrocatalytic activity in this series of MOFs by showing a 10mAcm-2 OER current density at 357mV overpotential and an ORR half-wave potential at 0.83V versus reversible hydrogen electrode (RHE). Theoretical studies revealed the synergistic effect of two proximal Co atoms in the Co4(SO4)4 cluster in OER by facilitating the formation of O─O bonds. This work is of fundamental significance to present the construction of Co4(SO4)4 clusters in framework structures for oxygen electrocatalysis and to demonstrate the cooperation between two proximal Co atoms in such clusters during the O─O bond formation process.

Facilitating charge transfer via a Semi-Coherent Fe(PO3)2-Co2P2O7 heterointerface for highly efficient Zn-Air batteries

Developing reversible oxygen electrodes for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for achieving high-performance rechargeable Zn-air batteries (ZABs). This study introduced an nitrogen-doped carbon confined with a semi-coherent Fe(PO3)2-Co2P2O7 heterojunction for bifunctional oxygen electrocatalysis. This nanocomposite yielded an ORR half-wave potential of 0.908 V and an OER overpotential of 291 mV at 10 mA/cm2. ZABs incorporating this catalyst yielded impressive performance, including a peak power density of 203 mW/cm2, a specific capacity of 737 mAh/gZn, and promoted stability. Both experimental and theoretical simulations demonstrated that the unique electric field between Fe(PO3)2 and Co2P2O7 promoted efficient charge transport across the heterointerface. This interaction likely modulated the d-band center of the heterojunction, expedite the desorption of oxygen intermediates, thus improving oxygen catalysis and, consequently, ZAB performance. This work illustrates a significant design principle for creating efficient bifunctional catalysts in energy conversion technologies.

A Superior Bifunctional Electrocatalyst in Which Directional Electron Transfer Occurs Between a Co/Ni Alloy and Fe─N─C Support.

Stable, efficient, and economical bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are needed for rechargeable Zn-air batteries. In this study, a directional electron transfer pathway is exploited in a spatial heterojunction of CoyNix@Fe─N─C heterogeneous catalyst for effective bifunctional electrolysis (OER/ORR). Thereinto, the Co/Ni alloy is strongly coupled to the Fe─N─C support through Co/Ni─N bonds. DFT calculations and experimental findings confirm that Co/Ni─N bonds play a bridging role in the directional electron transfer from Co/Ni alloy to the Fe─N─C support, increasing the content of pyridinic nitrogen in the ORR-active support. In addition, the discovered directional electron transfer mechanism enhances both the ORR/OER activity and the durability of the catalyst. The Co0.66Ni0.34@Fe─N─C with the optimal Ni/Co ratio exhibits satisfying bifunctional electrocatalytic performance, requiring an ORR half-wave potential of 0.90V and an OER overpotential of 317mV at 10mA cm-2 in alkaline electrolytes. The assembled rechargeable zinc-air batteries (ZABs) incorporating Co0.66Ni0.34@Fe─N─C cathode exhibits a charge-discharge voltage gap comparable to the Pt/C||IrO2 assembly and high robustness for over 60h at 20mA cm-2.

CuNi alloy anchored on dual-substrate TiOx/N-doped carbon nanofibers as a bifunctional electrocatalyst for rechargeable zinc-air batteries

Development of non-noble metal-based electrocatalysts to enhance the performance of zinc-air batteries (ZABs) is of great significance, but it remains a formidable challenge due to their poor stability and activity. Herein, a bifunctional CuNi-TiOx/NCNFS electrocatalyst, featuring with electron-rich copper-nickel (CuNi) alloy nanoparticles anchored on titanium oxide/N-doped carbon nanofibers (TiOx/NCNFS), is constructed by a dual-substrate loading strategy. The introduction of TiOx has led to a significant increase in the stability of the dual-substrate. The strong electronic interaction between CuNi and TiOx strengthens the anchoring of active metal sites, thus accelerating the electron transfer. Theoretical calculations unclose that NCNFS can regulate the charge distribution of TiOx, inducing the charge transfer from NCNFS → TiOx → CuNi, thereby reducing the d-band center of Cu and Ni, which is beneficial to the desorption of intermediate oxide species of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Therefore, CuNi-TiOx/NCNFS delivers a remarkable bifunctional performance with a low OER overpotential of 258 mV at 10 mA cm−2 and an ORR half-wave potential of 0.85 V. When assembled into ZABs, CuNi-TiOx/NCNFS shows a low potential gap of 0.64 V, a higher power density of 149.6 mW cm−2 at 330 mA cm−2, and an outstanding stability for 250 h at 5mA cm−2. This study provides a novel approach by constructing dual-substrate to tune the electronic structure of active metal sites for efficient rechargeable ZABs.

Performance enhancement of rechargeable zinc-air battery through synergistic ex-solution of multi-component Pt/CoWO4-x catalysts

Advancing zinc-air battery (ZAB) technology necessitates the development of air cathode electrocatalyst systems that demonstrate high reactivity and stability. We introduce a novel method to fabricate a robust catalyst-support hybrid. This hybrid comprises Co-doped Pt nanoparticles (NPs) anchored on metal oxide (Ex-PtCoWO) nanofibers (NFs), synthesized via electrospinning followed by selective metal ex-solution. Controlling the ex-solution of metal NPs leads to a highly active and stable oxygen reduction reaction (ORR). Moreover, the three-dimensional CoWO4-x NFs network enhances the surface exposure of ex-solved metal NPs, thereby aiding both selective ex-solution and the provision of active sites for the oxygen evolution reaction (OER) during ZAB recharge. The Ex-PtCoWO NF exhibits an ORR half-wave potential of 0.89 V and an OER potential of 1.69 V at 10 mA cm−2 in alkaline media. ZABs utilizing Ex-PtCoWO NF show an extended cycle life of over 240 h with reduced charge-discharge polarization, compared to commercial catalysts.

Nickel-Induced charge transfer in semicoherent Co-Ni/Co6Mo6C Heterostructures for reversible oxygen electrocatalysis

To achieve high-performance Zn-air batteries (ZABs), the development of bifunctional air electrodes capable of efficiently mediating both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is imperative. In this study, we present an N-doped carbon hollow nanorod encapsulating a semi-coherent Co-Ni/Co6Mo6C heterojunction, tailored for reversible oxygen catalysis. This nanohybrid demonstrated an ORR half-wave potential of 0.907 V alongside an OER overpotential of η10 = 352 mV. When incorporated into ZABs, this catalyst exhibited extraordinary performance metrics, including a high-power density of 343.7 mW/cm2, a specific capacity of 681 mAh/gZn, and enhanced durability. The distinctive electric field within the heterojunction facilitated electron transfer across the semi-coherent interface during reversible oxygen electrocatalysis, enhancing the adsorption and release of active intermediates. Thus, this heightened ORR-OER catalytic efficiency culminated in superior ZABs performance. Our findings afford a pivotal design paradigm for the advancement of productive bifunctional catalysts within the field of energy conversion technologies.

Hierarchical porous Mn-Nx-doped carbons with ultrahigh surface area for effective electrocatalytic oxygen reduction

A MnCl2-ZnCl2 molten salt pyrolysis combining with silica template strategy was developed to produce hierarchical porous N-doped carbons with ultrahigh surface area of 3006 m2/g, employing phenol formaldehyde resin@silica as the precursors. The resultant Mn-Nx-doped carbons showcased remarkable electrocatalytic performance for oxygen reduction reaction (ORR) in 0.1 M KOH, attaining a notable ORR half-wave potential of 0.84 VRHE. It also indicated higher open circuit and power density in home-made zinc-air batteries. This research offers a distinctive molten salt pyrolysis and template combining approach to generate ultrahigh-surface-area carbons with advanced electrocatalytic capabilities.

Single-atom Mn sites confined into hierarchically porous core–shell nanostructures for improved catalysis of oxygen reduction

Applications of zinc-air batteries are partially limited by the slow kinetics of oxygen reduction reaction (ORR); Thus, developing effective strategies to address the compatibility issue between performance and stability is crucial, yet it remains a significant challenge. Here, we propose an in situ gas etching-thermal assembly strategy with an in situ-grown graphene-like shell that will favor Mn anchoring. Gas etching allows for the simultaneous creation of mesopore-dominated carbon cores and ultrathin carbon layer shells adorned entirely with highly dispersed Mn-N4 single-atom sites. This approach effectively resolves the compatibility issue between activity and stability in a single step. The unique core–shell structure allows for the full exposure of active sites and effectively prevents the agglomerations and dissolution of Mn-N4 sites in cores. The corresponding half-wave potential for ORR is up to 0.875 V (vs. reversible hydrogen electrode (RHE)) in 0.1 M KOH. The gained catalyst (Mn-N@Gra-L)-assembled zinc-air battery has a high peak power density (242 mW cm−2) and a durability of ∼ 115 h. Furthermore, replacing the zinc anode achieved a stable cyclic discharge platform of ∼ 20 h at varying current densities. Forming more fully exposed and stable existing Mn-N4 sites is a governing factor for improving the electrocatalytic ORR activity, significantly cycling durability, and reversibility of zinc-air batteries.

Healing the structural defects of spinel MnFe2O4 to enhance the electrocatalytic activity for oxygen reduction reaction

Spinel metal oxides containing Mn, Co, or Fe (AB2O4, A/B = Mn/Fe/Co) are one of the most promising non-Pt electrocatalysts for oxygen reduction reaction (ORR) in alkaline conditions. However, the low conductivity of metal oxides and the poor intrinsic activities of transition metal sites lead to unsatisfactory ORR performance. In this study, eutectic molten salt (EMS) treatment is employed to reconstruct the atomic arrangement of MnFe2O4 electrocatalyst as a prototype for enhancing ORR performance. Comprehensive analyses by using XAFS, soft XAS, XPS, and electrochemical methods reveal that the EMS treatment reduces the oxygen vacancies and spinel inverse in MnFe2O4 effectively, which improves the electric conductivity and increases the population of more catalytically active Mn2+ sites with tetrahedral coordination. Moreover, the enhanced Mn-O interaction after EMS treatment is conducive to the adsorption and activation of O2, which promotes the first electron transfer step (generally considered as the rate-determining step) of the ORR process. As a result, the EMS treated MnFe2O4 catalyst delivers a positive shift of 40 mV in the ORR half-wave potential and a two-fold enhanced mass/specific activity. This work provides a convenient approach to manipulate the atomic architecture and local electronic structure of spinel oxides as ORR electrocatalysts and a comprehensive understanding of the structure-performance relationship from the molecular/atomic scale.

MIL-101(Fe)-derivatized cathode as an efficient oxygen electrocatalyst for rechargeable Zn-air battery

The exploration of multifunctional electrocatalysts with cost-effective and high kinetic activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for the development of advanced energy conversion and storage equipment. Herein, a novel hierarchical mesoporous/macropores MIL-101(Fe) derivative carbon catalyst material was prepared by a simple molten ZnCl2-assisted synthesis route. Specifically, 1H-benzotriazole (BTA) organic ligands were intentionally introduced as nitrogen sources in order to induce the formation of charge-rich regions through an electronegative nitrogen doping control strategy, and most importantly, the lone pair electron-rich nature of element N could facilitate the separation and anchoring of iron species enchanted the utilization rate of active sites. Because of these properties, the as-prepared catalyst (denoted as FeSACs/NxC) possesses unrivalled bifunction electrocatalytic activity and durability for the ORR and OER. The FeSACs/N1.25C as working electrode exhibits a quite satisfactory electrochemical performance for the ORR (half-wave potential of 0.82 V) and OER (a small overpotential of 302 mV at 10 mA cm−2) in the classic three-electrode configuration. Moreover, the FeSACs/N1.25C-based air cathode imparts encouraging performance in a rechargeable Zn–air battery prototype with an open-circuit voltage of 1.45 V, a specific capacity of 792.16 mAh g−1, an energy density of 871.38 Wh kg−1, and excellent stability for 120 h. This work has opened the way for the development of low-cost, fast kinetic and stable non-noble metal multifunctional catalysts.

Metal–organic framework–derived trimetallic particles encapsulated by ultrathin nitrogen-doped carbon nanosheets on a network of nitrogen-doped carbon nanotubes as bifunctional catalysts for rechargeable zinc–air batteries

Economical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional catalysts with high activity aimed at replacing precious metal catalysts for rechargeable zinc-air batteries (ZABs) must be developed. In this study, a multiple hierarchical-structural material is developed using a facile dielectric barrier discharge (DBD) plasma surface treatment, solvothermal reaction, and high-temperature carbonization strategy. This strategy allows for the construction of nanosheets using nitrogen-doped carbon (NC) material-encapsulated ternary CoNiFe alloy nanoparticles (NPs) on a network of NC nanotubes (NCNTs), denoted as CoNiFe–NC@p–NCNTs. Precisely, the presence of abundant CoNiFe alloy NPs and the formation of M–N–C active sites created by transition metals (cobalt, nickel, and iron) coupled with NC can provide superior OER/ORR bifunctional properties. Moreover, the prepared NC layers with a multilevel pore structure contribute to a larger specific surface area, exposing numerous active sites and enhancing the uniformity of electron and mass movement. The CoNiFe0.08–NC@p–NCNTs show remarkable dual functionality for electrochemical oxygen reactions (ORR half-wave potential of 0.811 V, limiting current density of 5.73 mA cm−2 measured with a rotating disk electrode at a rotation speed of 1600 rpm, and OER overpotential of 351 mV at 10 mA cm−2), which demonstrates similar ORR performance to 20 wt% Pt/C and better OER performance than the commercial RuO2. A liquid ZAB prepared using the proposed material has excellent bifunctionality with an open-circuit voltage of 1.450 V and long-term cycling stability of 230 h@10 mA cm−2.

Sulfur doping triggers charge redistribution at the heterointerface of Fe-N-C supported ultralow-Pt-loading electrocatalysts for efficient oxygen reduction

Development of low Pt-loading electrocatalyst with enhanced activity towards oxygen reduction reaction (ORR) is highly demanded for widespread penetration of clean energy technologies. Heterointerface regulation can effectively optimize the electronic structure and intrinsic activity of the carbon supported Pt-based electrocatalyst to reduce Pt consumption. Here, by judicious choice of a sulfur-doped Fe-N-C (Fe-NS-C) as support, we construct a novel Pt/Fe-N-C heterointerface with sulfur incorporation and develop a hybrid electrocatalyst (denoted as Pt@Fe-NS-C) with ultralow Pt-loading (1.51 wt%). The incorporation of sulfur triggers the charge redistribution at the heterointerface and reduces the electron transfer from Pt to Fe-NS-C, prompting the electron density around Pt sites and boosting the electrocatalytic performance towards ORR (half-wave potential: 0.903 V; mass activity of 1.28 A mg−1Pt at 0.9 V). In comparison, Pt species dispersed onto Fe-N-C without sulfur doping (Pt@Fe-N-C) are electron-deficient, which is not conductive to activate O2 and results in inferior ORR activity. Zinc-air battery fabricated with Pt@Fe-NS-C as the cathode catalysts shows a large peak power density and a specific capacity of 806.7 mAh g−1Zn. This work offers an effective way to tailor the heterointerface of hybrid or supported electrocatalyst with optimized electronic structures towards advanced electrocatalysis.

In-Situ Nanoarchitectonics of Fe/Co LDH over Cobalt-Enriched N-Doped Carbon Cookies as Facile Oxygen Redox Electrocatalysts for High-Rate Rechargeable Zinc-Air Batteries.

The reality of long-term rechargeable and high-performance zinc-air batteries relies majorly on cost-effective and eminent bifunctional electrocatalysts, which can perform both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Herein, we demonstrate a new approach for the synthesis of in-situ-grown layered double hydroxide of iron and cobalt over a cobalt nanoparticle-enriched nitrogen-doped carbon frame (CoL 2:1) by a simple coprecipitation reaction with facile scale-up and explore its electrocatalytic ORR and OER activity for an electrically rechargeable zinc-air battery. Consequently, the developed composite displays excellent ORR and OER activity with an ORR half-wave potential of 0.84 V, a limiting current density of 5.85 mA/cm2, and an OER overpotential of 320 mV with exceptional stability. The outstanding bifunctionality index of the catalyst (ΔE = 0.72 V) inspired us to utilize it as a cathode catalyst in an in-house developed prototype zinc-air battery. The battery could easily supply a specific capacity of 804 mAh/g with a maximum peak power density of 161 mW/cm2. The battery exhibits an attractive charge-discharge profile with a lesser voltage gap of 0.76 V at 10 mA/cm2 with durability for a period of 200 h and a voltage efficiency of 97%, which surpassed the corresponding Pt/C + RuO2-based zinc-air battery. Further, a maximum load of 50 mA/cm2 could easily be sustained during cycling, revealing its outstanding stability. A series-connected two CoL 2:1-based zinc-air batteries effortlessly enlighten a pinwheel fan and LED panel simultaneously, revealing its practicality. The high electrical conductivity and greater specific surface area of Co/N-C and its robust attachment with Fe/Co LDH preserves both active sites, thereby resulting in exceptional performance. Our method is capable of being flexible enough to create various bifunctional Co/N-C-based composite electrodes, opening up a feasible pathway to rechargeable zinc-air batteries with maximum energy density.

2D Metal Porphyrin-Based MOFs and ZIF-8 Composite-Derived Carbon Materials Containing M-Nx Active Sites as Bifunctional Electrocatalysts for Zinc-Air Batteries.

The main impediment to the development of zinc-air batteries is the sluggish kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Transition metal N-doped carbon catalysts offer a promising alternative to noble metal catalysts, with metal-organic framework (MOF)-derived carbon material catalysts being particularly noteworthy. Here, we synthesized MxP-Z-C carbon catalysts by combining two-dimensional (2D) metal porphyrin-based MOFs (MxPMFs, x = Fe, Co, Ni, Mn) and three-dimensional zeolitic imidazole framework-8 (ZIF-8) through electrostatic interaction, followed by carbonization. ZIF-8 was inserted between the layers of MxPMFs to prevent its Π-Π stacking, allowing the active sites to become fully exposed. MxP-Z-C demonstrated an impressive catalytic activity for both the ORR and the OER reactions. Among them, FeP-Z-C showed the best catalytic activity. The half-wave potential for ORR was 0.92 V (vs the reversible hydrogen electrode (RHE)), while the overpotential for the OER was 290 mV. In addition, the zinc-air battery assembled by FeP-Z-C exhibited high power density (133.14 mW cm-2) and significant specific capacity (816 mAh gZn-1), indicating considerable potential as a bifunctional catalyst for electronic devices.