Atomically dispersed cobalt catalyst anchored on nitrogen-doped carbon nanosheets for lithium-oxygen batteries

Robust oxygen adsorbent mediated oxygen redox reactions for high performance lithium-oxygen battery

Lithium-oxygen batteries (LOBs) have been widely studied because of their ultra-high energy density (∼3500 Wh kg-1). However, the reversibility and stability of LOBs are greatly limited by the sluggish kinetics of oxygen reduction/evolution reactions (ORR/OER) and severely parasitic reactions on oxygen electrodes. Electrolyte in LOBs plays an important role in the transport of reactive oxygen species and Li+, which greatly affects the kinetics and reversibility of the charging and discharging processes of batteries. In this work, perfluorooctane (PFO) is used as the additive in 1.0 M LiTFSI/TEGDEM electrolyte for LOBs to regulate the kinetics of oxygen electrode reactions. Due to the strong adsorption ability of PE toward oxygen, the oxygen concentration inside the electrolyte is greatly increased after the addition of PE. In addition, the PE-added electrolyte also exhibits superior electrochemical stability and is capable of triggering solution-mediated Li2O2 growth pathway during the discharge process of the LOBs. Therefore, with the increased oxygen concentration and the optimized electrode/electrolyte interface, the ORR/OER kinetics on the oxygen electrode is significantly promoted, which enables the LOBs with excellent energy efficiency and cycling life. This work provides a new idea for the design of oxygen-rich and high-performance electrolyte for lithium-oxygen batteries.

Beyond Catalysts: Exploring Discharge Product Growth and Intrinsic Overpotential in Lithium-Oxygen Batteries

The lithium-oxygen (Li-O2) battery, renowned for its exceptionally high theoretical energy density, is poised to revolutionize next-generation energy storage systems. However, its practical application depends on overcoming several challenges, particularly the high cathode overpotential, which significantly diminishes the battery's energy efficiency and durability. This study delves into the interactions at the cathode surface during oxygen reduction and evolution reactions (ORR/OER), extending the analysis beyond the initial reaction stages to encompass the extensive charge-discharge process. We introduce and define the concepts of intrinsic equilibrium potential and intrinsic overpotential, demonstrating that these critical parameters are predominantly influenced by the growth of discharge products, rather than the catalysts, thereby underscoring the inherent properties of the battery. This shift in focus from merely enhancing cathode catalysts to understanding and leveraging the intrinsic characteristics of the battery discharge process opens new avenues for optimizing and enhancing the performance of large-scale Li-O2 batteries. Furthermore, our findings indicate potential broader applications to other metal-oxygen systems, paving the way for the design of high-capacity, high-efficiency energy storage technologies.

General In Situ Engineering of Carbon-Based Materials on Carbon Fiber for In Vivo Neurochemical Sensing

Developing real-time, dynamic, and in situ analytical methods with high spatial and temporal resolutions is crucial for exploring biochemical processes in the brain. Although in vivo electrochemical methods based on carbon fiber (CF) microelectrodes are effective in monitoring neurochemical dynamics during physiological and pathological processes, complex post modification hinders large-scale productions and widespread neuroscience applications. Herein, we develop a general strategy for the in situ engineering of carbon-based materials to mass-produce functional CFs by introducing polydopamine to anchor zeolitic imidazolate frameworks as precursors, followed by one-step pyrolysis. This strategy demonstrates exceptional universality and design flexibility, overcoming complex post-modification procedures and avoiding the delamination of the modification layer. This simplifies the fabrication and integration of functional CF-based microelectrodes. Moreover, we design highly stable and selective H+, O2, and ascorbate microsensors and monitor the influence of CO2 exposure on the O2 content of the cerebral tissue during physiological and ischemia-reperfusion pathological processes.

Unleashing the potential of Li-O2 batteries with electronic modulation and lattice strain in pre-lithiated electrocatalysts

Efficient catalysts are indispensable for overcoming the sluggish reaction kinetics and high overpotentials inherent in Li-O2 batteries. However, the lack of precise control over catalyst structures at the atomic level and limited understanding of the underlying catalytic mechanisms pose significant challenges to advancing catalyst technology. In this study, we propose the concept of precisely controlled pre-lithiated electrocatalysts, drawing inspiration from lithium electrochemistry. Our results demonstrate that Li+ intercalation induces lattice strain in RuO2 and modulates its electronic structure. These modifications promote electron transfer between catalysts and reaction intermediates, optimizing the adsorption behavior of Li-O intermediates. As a result, Li-O2 batteries employing Li0.52RuO2 exhibit ultrahigh energy efficiency, long lifespan, high discharge capacity, and excellent rate performance. This research offers valuable insights for the design and optimization of efficient electrocatalysts at the atomic level, paving the way for further advancements in Li-O2 battery technology.

Recent advances of two-dimensional materials-based heterostructures for rechargeable batteries

Because of their unique layer structure, 2D materials have demonstrated to be promising electrode materials for rechargeable batteries. However, individual 2D materials cannot meet all the performance requirements of energy density, power density, and cycle life. Constructing 2D materials-based heterostructures offers an opportunity to synergistically handle the deficiencies of individual 2D materials and modulate the physical and electrochemical properties. The enlarged interlayer distance and increased binding energy with ions of heterostructures can facilitate charge transfer, boost electrochemical reactivities, resulting in an enhanced performance in rechargeable batteries. Here we summarize the latest development of heterostructures consisted of 2D materials and their applications in rechargeable batteries. Firstly, different preparation strategies and optimized structure engineering strategies of 2D materials-based heterostructures are systematically introduced. Secondly, the unique functions of 2D materials-based heterostructures in rechargeable batteries are discussed respectively. Finally, challenges and perspectives are presented to inspire the future study of 2D materials-based heterostructures.

Constructing an Interlaced Catalytic Surface via Fluorine-Doped Bimetallic Oxides for Oxygen Electrode Processes in Li-O2 Batteries

Lithium-oxygen (Li-O2) batteries, renowned for their high theoretical energy density, have garnered significant interest as prime candidates for future electric device development. However, their actual capacity is often unsatisfactory due to the passivation of active sites by solid-phase discharge products. Optimizing the growth and storage of these products is a crucial step in advancing Li-O2 batteries. Here, a fluorine-doped bimetallic cobalt-nickel oxide (CoNiO2- xFx/CC) with an interlaced catalytic surface (ICS) and a corncob-like structure is proposed as an oxygen electrode. Unlike conventional oxide electrodes with a "single adsorption catalytic mechanism," the ICS of CoNiO2- xFx/CC offers a "competitive adsorption catalytic mechanism," where oxygen sites facilitate oxygen conversion while fluorine sites contribute to the growth of Li2O2. This results in a change in Li2O2 morphology from a surface film to toroidal particles, effectively preventing the burial of active sites. Additionally, the unique open architecture aids in the capture and release of oxygen and the formation of well-contacted Li2O2/electrode interfaces, which benefits the complete decomposition of Li2O2 products. Consequently, the Li-O2 battery with a CoNiO2- xFx/CC cathode demonstrates a high specific capacity of up to 30923 mAh g-1 and a lifespan exceeding 580 cycles, surpassing most reported metal oxide-based cathodes.

Constructed Mott-Schottky Heterostructure Catalyst to Trigger Interface Disturbance and Manipulate Redox Kinetics in Li-O2 Battery

Lithium-oxygen batteries (LOBs) with high energy density are a promising advanced energy storage technology. However, the slow cathodic redox kinetics during cycling causes the discharge products to fail to decompose in time, resulting in large polarization and battery failure in a short time. Therefore, a self-supporting interconnected nanosheet array network NiCo2O4/MnO2 with a Mott-Schottky heterostructure on titanium paper (TP-NCO/MO) is ingeniously designed as an efficient cathode catalyst material for LOBs. This heterostructure can accelerate electron transfer and influence the charge transfer process during adsorption of intermediate by triggering the interface disturbance at the heterogeneous interface, thus accelerating oxygen reduction and oxygen evolution kinetics and regulating product decomposition, which is expected to solve the above problems. The meticulously designed unique structural advantages enable the TP-NCO/MO cathode catalyst to exhibit an astounding ultra-long cycle life of 800 cycles and an extraordinarily low overpotential of 0.73 V. This study utilizes a simple method to cleverly regulate the morphology of the discharge products by constructing a Mott-Schottky heterostructure, providing important reference for the design of efficient catalysts aimed at optimizing the adsorption of reaction intermediates.

2D MXene/MBene Superlattice with Narrow Bandgap as Superior Electrocatalyst for High-Performance Lithium-Oxygen Battery

Lithium-oxygen (Li-O2) battery with large theoretical energy density (≈3500 Wh kg-1) is one of the most promising energy storage and conversion systems. However, the slow kinetics of oxygen electrode reactions inhibit the practical application of Li-O2 battery. Thus, designing efficient electrocatalysts is crucial to improve battery performance. Here, Ti3C2 MXene/Mo4/3B2-x MBene superlattice is fabricated its electrocatalytic activity toward oxygen redox reactions in Li-O2 battery is studied. It is found that the built-in electric field formed by a large work function difference between Ti3C2 and Mo4/3B2-x will power the charge transfer at the interface from titanium (Ti) site in Ti3C2 to molybdenum (Mo) site in Mo4/3B2-x. This charge transfer increases the electron density in 4d orbital of Mo site and decreases the d-band center of Mo site, thus optimizing the adsorption of intermediate product LiO2 at Mo site and accelerating the kinetics of oxygen electrode reactions. Meanwhile, the formed film-like discharge products (Li2O2) improve the contact with electrode and facilitate the decomposition of Li2O2. Based on the above advantages, the Ti3C2 MXene/Mo4/3B2-x MBene superlattice-based Li-O2 battery exhibits large discharge specific capacity (17 167 mAh g-1), low overpotential (1.16 V), and superior cycling performance (475 cycles).

Oxygen-bridging Fe, Co dual-metal dimers boost reversible oxygen electrocatalysis for rechargeable Zn-air batteries

Rechargeable zinc-air batteries (ZABs) are regarded as a remarkably promising alternative to current lithium-ion batteries, addressing the requirements for large-scale high-energy storage. Nevertheless, the sluggish kinetics involving oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) hamper the widespread application of ZABs, necessitating the development of high-efficiency and durable bifunctional electrocatalysts. Here, we report oxygen atom-bridged Fe, Co dual-metal dimers (FeOCo-SAD), in which the active site Fe-O-Co-N6 moiety boosts exceptional reversible activity toward ORR and OER in alkaline electrolytes. Specifically, FeOCo-SAD achieves a half-wave potential (E1/2) of 0.87 V for ORR and an overpotential of 310 mV at a current density of 10 mA cm-2 for OER, with a potential gap (ΔE) of only 0.67 V. Meanwhile, FeOCo-SAD manifests high performance with a peak power density of 241.24 mW cm-2 in realistic rechargeable ZABs. Theoretical calculations demonstrate that the introduction of an oxygen bridge in the Fe, Co dimer induced charge spatial redistribution around Fe and Co atoms. This enhances the activation of oxygen and optimizes the adsorption/desorption dynamics of reaction intermediates. Consequently, energy barriers are effectively reduced, leading to a strong promotion of intrinsic activity toward ORR and OER. This work suggests that oxygen-bridging dual-metal dimers offer promising prospects for significantly enhancing the performance of reversible oxygen electrocatalysis and for creating innovative catalysts that exhibit synergistic effects and electronic states.

Single Atom Catalysts Based on Earth-Abundant Metals for Energy-Related Applications

Anthropogenic activities related to population growth, economic development, technological advances, and changes in lifestyle and climate patterns result in a continuous increase in energy consumption. At the same time, the rare metal elements frequently deployed as catalysts in energy related processes are not only costly in view of their low natural abundance, but their availability is often further limited due to geopolitical reasons. Thus, electrochemical energy storage and conversion with earth-abundant metals, mainly in the form of single-atom catalysts (SACs), are highly relevant and timely technologies. In this review the application of earth-abundant SACs in electrochemical energy storage and electrocatalytic conversion of chemicals to fuels or products with high energy content is discussed. The oxygen reduction reaction is also appraised, which is primarily harnessed in fuel cell technologies and metal-air batteries. The coordination, active sites, and mechanistic aspects of transition metal SACs are analyzed for two-electron and four-electron reaction pathways. Further, the electrochemical water splitting with SACs toward green hydrogen fuel is discussed in terms of not only hydrogen evolution reaction but also oxygen evolution reaction. Similarly, the production of ammonia as a clean fuel via electrocatalytic nitrogen reduction reaction is portrayed, highlighting the potential of earth-abundant single metal species.

Nanoengineering of Cathode Catalysts for Li-O2 Batteries

Lithium-oxygen (Li-O2) batteries have obtained widespread attention as next-generation energy storage systems due to their extremely high energy density. However, the high charge overpotential, attributed to the insulating property of Li2O2, significantly limits the energy efficiency and triggers solvent degradation. The high electrochemical activities of oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) on the cathode are crucial for alleviating the high charging polarizations and enhancing the lifetime of Li-O2 batteries, which are also top challenges of state-of-art research. In this review, the scientific challenges and the proposed solutions in the development of cathode catalysts have been summarized. The recent research advancements on the nanoengineering of cathode catalysts for Li-O2 batteries have been comprehensively discussed, and the perspectives on the structure optimization are presented. Meanwhile, we have elucidated the structure-performance relationship between the electronic state and performance of the cathode catalysts at the nanoscale level. This review intends to provide guidelines for the design and construction of cathode catalysts in advanced Li-O2 batteries.

Coupling Ni Single Atomic Sites with Metallic Aggregates at Adjacent Geometry on Carbon Support for Efficient Hydrogen Peroxide Electrosynthesis

Single atomic catalysts have shown great potential in efficiently electro-converting O2 to H2O2 with high selectivity. However, the impact of coordination environment and introduction of extra metallic aggregates on catalytic performance still remains unclear. Herein, first a series of carbon-based catalysts with embedded coupling Ni single atomic sites and corresponding metallic nanoparticles at adjacent geometry is synthesized. Careful performance evaluation reveals NiSA/NiNP-NSCNT catalyst with precisely controlled active centers of synergetic adjacent Ni-N4S single sites and crystalline Ni nanoparticles exhibits a high H2O2 selectivity over 92.7% within a wide potential range (maximum selectivity can reach 98.4%). Theoretical studies uncover that spatially coupling single atomic NiN4S sites with metallic Ni aggregates in close proximity can optimize the adsorption behavior of key intermediates *OOH to achieve a nearly ideal binding strength, which thus affording a kinetically favorable pathway for H2O2 production. This strategy of manipulating the interaction between single atoms and metallic aggregates offers a promising direction to design new high-performance catalysts for practical H2O2 electrosynthesis.

Polyoxometalate Supported Single Transition Metal Atom as a Redox Mediator for Li-O2 Batteries

Keggin-type polyoxometalate (POM) supported single transition metal (TM) atom (TM1/POM) as an efficient soluble redox mediator for Li-O2 batteries is comprehensively investigated by first-principles calculations. Among the pristine POM and four kinds of TM1/POM (TM = Fe, Co, Ni, and Pt), Co1/POM not only maintains good structural and thermodynamic stability in oxidized and reduced states but also exhibits promising electro(chemical) catalytic performance for both oxygen reduction reaction and oxygen evolution reaction (OER) in Li-O2 batteries with the lowest Gibbs free energy barriers. Further investigations demonstrate that the moderate binding strength of Li2-xO2 (x = 0, 1, and 2) intermediates on Co1/POM guarantees favorable Li2O2 formation and decomposition. Electronic structure analyses indicate that the introduced Co single atom as an electron transfer bridge can not only efficiently improve the electronic conductivity of POM but also regulate the bonding/antibonding states around the Fermi level of [Co1/POM-Li2O2]ox. The solvent effect on the OER catalytic performance and the electronic properties of [Co1/POM-Li2O2]ox with and without dimethyl sulfoxide solvent are also investigated.

Controllable Regulation of the Oxygen Redox Process in Lithium-Oxygen Batteries by High-Configuration-Entropy Spinel with an Asymmetric Octahedral Structure

Designing bifunctional electrocatalysts to boost oxygen redox reactions is critical for high-performance lithium-oxygen batteries (LOBs). In this work, high-entropy spinel (Co0.2Mn0.2Ni0.2Fe0.2Cr0.2)3O4 (HEOS) is fabricated by modulating the internal configuration entropy of spinel and studied as the oxygen electrode catalyst in LOBs. Under the high-entropy atomic environment, the Co-O octahedron in spinel undergoes asymmetric deformation, and the reconfiguration of the electron structure around the Co sites leads to the upward shift of the d-orbital centers of the Co sites toward the Fermi level, which is conducive to the strong adsorption of redox intermediate LiO2 on the surface of the HEOS, ultimately forming a layer of a highly dispersed Li2O2 thin film. Thin-film Li2O2 is beneficial for ion diffusion and electron transfer at the electrode-electrolyte interface, which makes the product easy to decompose during the charge process, ultimately accelerating the kinetics of oxygen redox reactions in LOBs. Based on the above advantages, HEOS-based LOBs deliver high discharge/charge capacity (12.61/11.72 mAh cm-2) and excellent cyclability (424 cycles). This work broadens the way for the design of cathode catalysts to improve oxygen redox kinetics in LOBs.

Ruthenium single-atom doping-driven modulation of Co3O4 spinel tetrahedral site 3d-orbital occupancy in lithium-oxygen batteries

Metal single-atom catalysts have attracted widespread attention in the field of lithium-oxygen batteries due to their unique active sites, high catalytic selectivity, and near total atomic utilization efficiency. Isolated metal atoms not only serve as the active sites themselves, but also function as modulators, reversely regulating the surface electronic structure of the support to enhance its inherent electrocatalytic activities. Despite the potential of isolated metal atom-driven active sites, understanding the structure-activity relationship remains a challenge. In this study, we present a ruthenium single-atom doping-driven cost-effective and durable tricobalt tetroxide electrocatalyst with excellent oxygen electrode electrocatalytic activity. The lithium-oxygen battery with this catalyst as the oxygen electrode demonstrates high performance, achieving a capacity of up to 25 000 mA h g-1 and maintaining good stability over 400 cycles at a current density of 100 mA g-1. This improvement is attributed to the exquisite control of the morphology and structure of the discharge product, lithium peroxide. The aresults of physical characterization and theoretical calculations reveal that isolated ruthenium atoms bond with the tetrahedral cobalt site, resulting in spin polarization enhancement and rearrangement of d orbital energy levels in cobalt. This rearrangement reduces the dz2 orbital occupancy and promotes their transfer to the octahedral cobalt site, thereby enhancing its adsorption capacity for the oxygen-containing intermediates, and ultimately increasing the electrocatalytic activity of the oxygen evolution reaction. This work presents an innovative strategy to regulate the catalytic activity of metal oxides by introducing another metal single atom.

Self-Catalyzed Growth of Co4N and N-Doped Carbon Nanotubes toward Bifunctional Cathode for Highly Safe and Flexible Li-Air Batteries

The practical application of high-energy density lithium-oxygen (Li-O2) batteries is severely impeded by the notorious cycling stability and safety, which mainly comes from slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at cathodes, causing inferior redox overpotentials and reactive lithium metal in flammable liquid electrolyte. Herein, a bifunctional electrode, a safe gel polymer electrolyte (GPE), and a robust lithium anode are proposed to alleviate above problems. The bifunctional electrode is composed of N-doped carbon nanotubes (N-CNTs) and Co4N by in situ chemical vapor deposition self-catalyzed growth on carbon cloth (N-CNTs@Co4N@CC). The self-supporting, binder-free N-CNTs@Co4N@CC electrode has a strong and stable three-dimensional (3D) interconnected conductive structure, which provides interconnectivity between the active sites and the electrode to promote the transfer of electrons. Furthermore, the N-CNT-intertwined Co4N ensures efficient catalytic activity. Hence, the electrode demonstrates improved electrochemical properties even under a large current density (2000 mA g-1) and long cycling operation (250 cycles). Moreover, a highly safe and flexible rechargeable cell using the 3D N-CNTs@Co4N@CC electrode, GPE, and robust lithium anode design has been explored. The open circuit voltage is stable at ∼3.0 V even after 9800 cycles, which proves the mechanical durability of the integrated GPE cell. The stable cable-type Li-air battery was demonstrated to stably drive the light-emitting diodes (LEDs), highlighting the reliability for practical use.

Coupling MoSe2 with Non-Stoichiometry Ni0.85 Se in Carbon Hollow Nanoflowers for Efficient Electrocatalytic Synergistic Effect on Li-O2 Batteries

Li-O2 batteries could deliver ultra-high theoretical energy density compared to current Li-ion batteries counterpart. The slow cathode reaction kinetics in Li-O2 batteries, however, limits their electrocatalytic performance. To this end, MoSe2 and Ni0.85 Se nanoflakes were decorated in carbon hollow nanoflowers, which were served as the cathode catalysts for Li-O2 batteries. The hexagonal Ni0.85 Se and MoSe2 show good structural compatibility with the same space group, resulting in a stable heterogeneous structure. The synergistic interaction of the unsaturated atoms and the built-in electric fields on the heterogeneous structure exposes abundant catalytically active sites, accelerating ion and charge transport and imparting superior electrochemical activity, including high specific capacities and stable cycling performance. More importantly, the lattice distances of the Ni0.85 Se (101) plane and MoSe2 (100) plane at the heterogeneous interfaces are highly matched to that of Li2 O2 (100) plane, facilitating epitaxial growth of Li2 O2 , as well as the formation and decomposition of discharge products during the cycles. This strategy of employing nonstoichiometric compounds to build heterojunctions and improve Li-O2 battery performance is expected to be applied to other energy storage or conversion systems.

Atomically Dispersed Zn/Co-N-C as ORR Electrocatalysts for Alkaline Fuel Cells

Hydrogen fuel cells have drawn increasing attention as one of the most promising next-generation power sources for future automotive transportation. Developing efficient, durable, and low-cost electrocatalysts, to accelerate the sluggish oxygen reduction reaction (ORR) kinetics, is urgently needed to advance fuel cell technologies. Herein, we report on metal-organic frameworks-derived nonprecious dual metal single-atom catalysts (SACs) (Zn/Co-N-C), consisting of Co-N4 and Zn-N4 local structures. These catalysts exhibited superior ORR activity with a half-wave potential (E1/2) of 0.938 V versus RHE (reversible hydrogen electrode) and robust stability (ΔE1/2 = -8.5 mV) after 50k electrochemical cycles. Moreover, this remarkable performance was validated under realistic fuel cell working conditions, achieving a record-high peak power density of ∼1 W cm-2 among the reported SACs for alkaline fuel cells. Operando X-ray absorption spectroscopy was conducted to identify the active sites and reveal catalytic mechanistic insights. The results indicated that the Co atom in the Co-N4 structure was the main catalytically active center, where one axial oxygenated species binds to form an Oads-Co-N4 moiety during the ORR. In addition, theoretical studies, based on a potential-dependent microkinetic model and core-level shift calculations, showed good agreement with the experimental results and provided insights into the bonding of oxygen species on Co-N4 centers during the ORR. This work provides a comprehensive mechanistic understanding of the active sites in the Zn/Co-N-C catalysts and will pave the way for the future design and advancement of high-performance single-site electrocatalysts for fuel cells and other energy applications.

Precise Design and Modification Engineering of Single-Atom Catalytic Materials for Oxygen Reduction

Due to their unique electronic and structural properties, single-atom catalytic materials (SACMs) hold great promise for the oxygen reduction reaction (ORR). Coordinating environmental and engineering strategies is the key to improving the ORR performance of SACMs. This review summarizes the latest research progress and breakthroughs of SACMs in the field of ORR catalysis. First, the research progress on the catalytic mechanism of SACMs acting on ORR is reviewed, including the latest research results on the origin of SACMs activity and the analysis of pre-adsorption mechanism. The study of the pre-adsorption mechanism is an important breakthrough direction to explore the origin of the high activity of SACMs and the practical and theoretical understanding of the catalytic process. Precise coordination environment modification, including in-plane, axial, and adjacent site modifications, can enhance the intrinsic catalytic activity of SACMs and promote the ORR process. Additionally, several engineering strategies are discussed, including multiple SACMs, high loading, and atomic site confinement. Multiple SACMs synergistically enhance catalytic activity and selectivity, while high loading can provide more active sites for catalytic reactions. Overall, this review provides important insights into the design of advanced catalysts for ORR.

Atomically Dispersed Ruthenium Catalysts with Open Hollow Structure for Lithium-Oxygen Batteries

Lithium-oxygen battery with ultra-high theoretical energy density is considered a highly competitive next-generation energy storage device, but its practical application is severely hindered by issues such as difficult decomposition of discharge products at present. Here, we have developed N-doped carbon anchored atomically dispersed Ru sites cathode catalyst with open hollow structure (h-RuNC) for Lithium-oxygen battery. On one hand, the abundance of atomically dispersed Ru sites can effectively catalyze the formation and decomposition of discharge products, thereby greatly enhancing the redox kinetics. On the other hand, the open hollow structure not only enhances the mass activity of atomically dispersed Ru sites but also improves the diffusion efficiency of catalytic molecules. Therefore, the excellent activity from atomically dispersed Ru sites and the enhanced diffusion from open hollow structure respectively improve the redox kinetics and cycling stability, ultimately achieving a high-performance lithium-oxygen battery.

Tunable Oxygen Vacancies of Cobalt Oxides in Lithium-Oxygen Batteries: Morphology Control of Discharge Product

The discharge product Li2O2 is difficult to decompose in lithium-oxygen batteries, resulting in poor reversibility and cycling stability of the battery, and the morphology of Li2O2 has a great influence on its decomposition during the charging process. Therefore, reasonable design of the catalyst structure to improve the density of catalyst active sites and make Li2O2 form a morphology which is easy to decompose in the charging process will help improve the performance of battery. Here, we demonstrate a series of hollow nanoboxes stacked by Co3O4 nanoparticles with different sizes. The results show that the surface of the nanoboxes composed of smaller size Co3O4 nanoparticles contains abundant pore structure and higher concentration of oxygen vacancies, which changes the adsorption energy of reactants and intermediates, providing more nucleation sites for Li2O2, thereby forming Li2O2 with high dispersion, which is easier to decompose during charging, and eventually improve the performance of the battery. This provides an important idea for the structural design of the cathode catalyst in lithium-oxygen batteries and the regulation of Li2O2 morphology.

Orthogonal-Channel, Low-Tortuosity Carbon Nanotube Platforms for High-Performance Li-O2 Batteries

Aerogels and foams are promising electrode materials owing to their lightweight, high porosity, and large surface area for creating abundant active/catalytic sites. Tailoring their porous structure is essential toward maximum electrode performance yet remains challenging in the field. Here, by modifying a pristine carbon nanotube (CNT) sponge with random internal distribution, we present a CNT platform consisting of regular, orthogonally intercrossed through-channels centered at a suitable lateral size (around 5 μm), with low tortuosity and enhanced electrochemical kinetics under predefined compression. Our CNT platforms, grafted by bifunctional transitional metal hydroxide catalyst, overcome considerable challenges of both long cycle life and high rates simultaneously, serving as Li-O2 cathodes and achieving lifetime of 500 cycles at 0.5 mA cm-2 (275 cycles even at 1 mA cm-2) and also displaying high areal capacity (27 mA h cm-2), which are superior to most of the recently reported porous electrodes based on various materials. The mechanism involving fast triple-phase transport and reversible discharge product deposition, enabled by catalyst-loaded orthogonal channels, has been disclosed. Such structure-tailored robust CNT platforms could find many applications in electrochemical catalysis and energy storage systems.

The Role of Self-Catalysis Induced by Co Doping in Nonaqueous Li-O2 Batteries

This work systematically studies the product self-catalysis of in situ electrochemical cobalt doping of Li2O2 and reveals its potential mechanism for improving the performance of lithium-oxygen (Li-O2) batteries. Theoretical calculations demonstrate that the discharge products contain substituted and interstitial Co impurities, which serve as active sites to promote the formation of Li3O4 crystallization, thus switching the nucleation mechanism from the main discharge product Li2O2 to Li3O4. This Co-doping behavior leads to the thermodynamically favorable and dynamically stable formation of Li3O4 crystals during the discharge process. Through systematic investigation of the structural, energetic, electronic, diffusive, and catalytic properties of the Co-doped Li2O2 and Li3O4 compounds, we found that Li3O4 has better charge/mass transport and a lower overpotential for the Li3O4 formation/decomposition reaction. Consequently, this work elucidates that Co doping provides a simple and effective approach for increasing the proportion of Li3O4, which can significantly improve the Li-O2 battery performance.

Fundamental mechanistic insights into the catalytic reactions of Li─S redox by Co single-atom electrocatalysts via operando methods

Lithium-sulfur batteries represent an attractive option for energy storage applications. A deeper understanding of the multistep lithium-sulfur reactions and the electrocatalytic mechanisms are required to develop advanced, high-performance batteries. We have systematically investigated the lithium-sulfur redox processes catalyzed by a cobalt single-atom electrocatalyst (Co-SAs/NC) via operando confocal Raman microscopy and x-ray absorption spectroscopy (XAS). The real-time observations, based on potentiostatic measurements, indicate that Co-SAs/NC efficiently accelerates the lithium-sulfur reduction/oxidation reactions, which display zero-order kinetics. Under galvanostatic discharge conditions, the typical stepwise mechanism of long-chain and intermediate-chain polysulfides is transformed to a concurrent pathway under electrocatalysis. In addition, operando cobalt K-edge XAS studies elucidate the potential-dependent evolution of cobalt's oxidation state and the formation of cobalt-sulfur bonds. Our work provides fundamental insights into the mechanisms of catalyzed lithium-sulfur reactions via operando methods, enabling a deeper understanding of electrocatalysis and interfacial dynamics in electrical energy storage systems.

Water-Trapping Single-Atom Co-N4 /Graphene Triggering Direct 4e- LiOH Chemistry for Rechargeable Aprotic Li-O2 Batteries

Lithium-oxygen (Li-O2 ) batteries have received extensive attention owing to ultrahigh theoretical energy density. Compared to typical discharge product Li2 O2 , LiOH has attracted much attention for its better chemical and electrochemical stability. Large-scale applications of Li-O2 batteries with LiOH chemistry are hampered by the serious internal shuttling of the water additives with the desired 4e- electrochemical reactions. Here, a metal organic framework-derived "water-trapping" single-atom-Co-N4 /graphene catalyst (Co-SA-rGO) is provided that successfully mitigates the water shuttling and enables the direct 4e- catalytic reaction of LiOH in the aprotic Li-O2 battery. The Co-N4 center is more active toward proton-coupled electron transfer, benefiting - direction 4e- formation of LiOH. 3D interlinked networks also provide large surface area and mesoporous structures to trap ≈12 wt% H2 O molecules and offer rapid tunnels for O2 diffusion and Li+ transportation. With these unique features, the Co-SA-rGO based Li-O2 battery delivers a high discharge platform of 2.83 V and a large discharge capacity of 12 760.8 mAh g-1 . Also, the battery can withstand corrosion in the air and maintain a stable discharge platform for 220 cycles. This work points out the direction of enhanced electron/proton transfer for the single-atom catalyst design in Li-O2 batteries.

Intrinsic Descriptor Guided Noble Metal Cathode Design for Li-CO2 Battery

To date, the effect of noble metal (NM) electronic structures on CO2 reaction activity remains unknown, and explicit screening criteria are still lacking for designing highly efficient catalysts in CO2 -breathing batteries. Herein, by preferentially considering the decomposition of key intermediate Li2 CO3 , an intrinsic descriptor constituted of thed x 2 - y 2 ${{\rm{d}}}_{{x}^2 - {y}^2}$ orbital states and the electronegativity for predicting high-performance cathode material are discovered. As a demonstration, a series of graphene-supported noble metals (NM@G) as cathodes are fabricated via a fast laser scribing technique. Consistent with the preliminary prediction, Pd@G exhibits an ultralow overpotential (0.41 V), along with superior cycling performance up to 1400 h. Moreover, the overall thermodynamic reaction pathways on NM@G confirm the reliability of the established intrinsic descriptor. This basic finding of the relationship between the electronic properties of noble metal cathodes and the performance of Li-CO2 batteries provides a novel avenue for designing remarkably efficient cathode materials for metal-CO2 batteries.

Insights into the solvation chemistry in liquid electrolytes for lithium-based rechargeable batteries

Lithium-based rechargeable batteries have dominated the energy storage field and attracted considerable research interest due to their excellent electrochemical performance. As indispensable and ubiquitous components, electrolytes play a pivotal role in not only transporting lithium ions, but also expanding the electrochemical stable potential window, suppressing the side reactions, and manipulating the redox mechanism, all of which are closely associated with the behavior of solvation chemistry in electrolytes. Thus, comprehensively understanding the solvation chemistry in electrolytes is of significant importance. Here we critically reviewed the development of electrolytes in various lithium-based rechargeable batteries including lithium-metal batteries (LMBs), nonaqueous lithium-ion batteries (LIBs), lithium-sulfur batteries (LSBs), lithium-oxygen batteries (LOBs), and aqueous lithium-ion batteries (ALIBs), and emphasized the effects of interactions between cations, anions, and solvents on solvation chemistry, and functions of solvation chemistry in different types of electrolytes (strong solvating electrolytes, moderate solvating electrolytes, and weak solvating electrolytes) on the electrochemical performance and redox mechanism in the abovementioned rechargeable batteries. Specifically, the significant effects of solvation chemistry on the stability of electrode-electrolyte interphases, suppression of lithium dendrites in LMBs, inhibition of the co-intercalation of solvents in LIBs, improvement of anodic stability at high cut-off voltages in LMBs, LIBs and ALIBs, regulation of redox pathways in LSBs and LOBs, and inhibition of hydrogen/oxygen evolution reactions in LOBs are thoroughly summarized. Finally, the review concludes with a prospective outlook, where practical issues of electrolytes, advanced in situ/operando techniques to illustrate the mechanism of solvation chemistry, and advanced theoretical calculation and simulation techniques such as "material knowledge informed machine learning" and "artificial intelligence (AI) + big data" driven strategies for high-performance electrolytes have been proposed.

Molten salt induced formation of chitosan based carbon nanosheets decorated with CoNx for boosting rechargeable Zn-air batteries

The earth-abundant, low-cost, and efficient oxygen electrode materials offer a potential opportunity to satisfy the large-scale production and application of metal-air batteries. Herein, a molten salt-assisted strategy is developed to anchor transition metal-based active sites via in-situ confining into porous carbon nanosheet. As a result, a chitosan-based porous nitrogen-doped nanosheet decorated with the well-defined CoN_x (CoN_x/CPCN) was reported. Both structural characterization and electrocatalytic mechanisms demonstrate a prominent synergetic effect between CoN_x and porous nitrogen-doped carbon nanosheets forcefully accelerates the sluggish reaction kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Interestingly, the Zn-air batteries (ZABs) equipped with CoN_x/CPCN-900 as an air electrode shows outstanding durability for 750 discharge/charge cycles, a high power density of 189.9 mW cm^-2, and a high gravimetric energy density of 1018.7 mWh g^-1 at 10 mA cm^-2. Furthermore, the assembled all-solid cell displays exceptional flexibility and power density (122.2 mW cm^-2).

Rapid production of kilogram-scale graphene nanoribbons with tunable interlayer spacing for an array of renewable energy

Graphene nanoribbons (GNRs) are widely recognized as intriguing building blocks for high-performance electronics and catalysis owing to their unique width-dependent bandgap and ample lone pair electrons on both sides of GNR, respectively, over the graphene nanosheet counterpart. However, it remains challenging to mass-produce kilogram-scale GNRs to render their practical applications. More importantly, the ability to intercalate nanofillers of interest within GNR enables in-situ large-scale dispersion and retains structural stability and properties of nanofillers for enhanced energy conversion and storage. This, however, has yet to be largely explored. Herein, we report a rapid, low-cost freezing-rolling-capillary compression strategy to yield GNRs at a kilogram scale with tunable interlayer spacing for situating a set of functional nanomaterials for electrochemical energy conversion and storage. Specifically, GNRs are created by sequential freezing, rolling, and capillary compression of large-sized graphene oxide nanosheets in liquid nitrogen, followed by pyrolysis. The interlayer spacing of GNRs can be conveniently regulated by tuning the amount of nanofillers of different dimensions added. As such, heteroatoms; metal single atoms; and 0D, 1D, and 2D nanomaterials can be readily in-situ intercalated into the GNR matrix, producing a rich variety of functional nanofiller-dispersed GNR nanocomposites. They manifest promising performance in electrocatalysis, battery, and supercapacitor due to excellent electronic conductivity, catalytic activity, and structural stability of the resulting GNR nanocomposites. The freezing-rolling-capillary compression strategy is facile, robust, and generalizable. It renders the creation of versatile GNR-derived nanocomposites with adjustable interlay spacing of GNR, thereby underpinning future advances in electronics and clean energy applications.

Edge-Site-Free and Topological-Defect-Rich Carbon Cathode for High-Performance Lithium-Oxygen Batteries

The rational design of a stable and catalytic carbon cathode is crucial for the development of rechargeable lithium-oxygen (LiO2 ) batteries. An edge-site-free and topological-defect-rich graphene-based material is proposed as a pure carbon cathode that drastically improves LiO2 battery performance, even in the absence of extra catalysts and mediators. The proposed graphene-based material is synthesized using the advanced template technique coupled with high-temperature annealing at 1800 °C. The material possesses an edge-site-free framework and mesoporosity, which is crucial to achieve excellent electrochemical stability and an ultra-large capacity (>6700 mAh g-1 ). Moreover, both experimental and theoretical structural characterization demonstrates the presence of a significant number of topological defects, which are non-hexagonal carbon rings in the graphene framework. In situ isotopic electrochemical mass spectrometry and theoretical calculations reveal the unique catalysis of topological defects in the formation of amorphous Li2 O2 , which may be decomposed at low potential (∼ 3.6 V versus Li/Li+ ) and leads to improved cycle performance. Furthermore, a flexible electrode sheet that excludes organic binders exhibits an extremely long lifetime of up to 307 cycles (>1535 h), in the absence of solid or soluble catalysts. These findings may be used to design robust carbon cathodes for LiO2 batteries.

Photothermal-enabled single-atom catalysts for high-efficiency hydrogen peroxide photosynthesis from natural seawater

Hydrogen peroxide (H₂O₂) is a powerful industrial oxidant and potential carbon-neutral liquid energy carrier. Sunlight-driven synthesis of H₂O₂ from the most earth-abundant O₂ and seawater is highly desirable. However, the solar-to-chemical efficiency of H₂O₂ synthesis in particulate photocatalysis systems is low. Here, we present a cooperative sunlight-driven photothermal-photocatalytic system based on cobalt single-atom supported on sulfur doped graphitic carbon nitride/reduced graphene oxide heterostructure (Co-CN@G) to boost H₂O₂ photosynthesis from natural seawater. By virtue of the photothermal effect and synergy between Co single atoms and the heterostructure, Co-CN@G enables a solar-to-chemical efficiency of more than 0.7% under simulated sunlight irradiation. Theoretical calculations verify that the single atoms combined with heterostructure significantly promote the charge separation, facilitate O₂ absorption and reduce the energy barriers for O₂ reduction and water oxidation, eventually boosting H₂O₂ photoproduction. The single-atom photothermal-photocatalytic materials may provide possibility of large-scale H₂O₂ production from inexhaustible seawater in a sustainable way.

New Conceptual Catalyst on Spatial High-Entropy Alloy Heterostructures for High-Performance Li-O2 Batteries

High-entropy alloys (HEAs) are attracting increased attention as an alternative to noble metals for various catalytic reactions. However, it is of great challenge and fundamental importance to develop spatial HEA heterostructures to manipulate d-band center of interfacial metal atoms and modulate electron-distribution to enhance electrocatalytic activity of HEA catalysts. Herein, an efficient strategy is demonstrated to construct unique well-designed HEAs spatial heterostructure electrocatalyst (HEA@Pt) as bifunctional cathode to accelerate oxygen reduction and evolution reaction (ORR/OER) kinetics for Li-O₂ batteries, where uniform Pt dendrites grow on PtRuFeCoNi HEA at a low angle boundary. Such atomically connected HEA spatial interfaces engender efficient electrons from HEA to Pt due to discrepancy of work functions, modulating electron distribution for fast interfacial electron transfer, and abundant active sites. Theoretical calculations reveal that electron redistribution manipulates d-band center of interfacial metal atoms, allowing appropriate adsorption energy of oxygen species to lower ORR/OER reaction barriers. Hence, Li-O₂ battery based on HEA@Pt electrocatalyst delivers a minimal polarization potential (0.37 V) and long-term cyclability (210 cycles) under a cut-off capacity of 1000 mAh g^-1 , surpassing most previously reported noble metal-based catalysts. This work provides significant insights on electron-modulation and d-band center optimization for advanced electrocatalysts.

Ambient Electrosynthesis toward Single-Atom Sites for Electrocatalytic Green Hydrogen Cycling

With the ultimate atomic utilization, well-defined configuration of active sites and unique electronic properties, catalysts with single-atom sites (SASs) exhibit appealing performance for electrocatalytic green hydrogen generation from water splitting and further utilization via hydrogen-oxygen fuel cells, such that a vast majority of synthetic strategies toward SAS-based catalysts (SASCs) are exploited. In particular, room-temperature electrosynthesis under atmospheric pressure offers a novel, safe, and effective route to access SASs. Herein, the recent progress in ambient electrosynthesis toward SASs for electrocatalytic sustainable hydrogen generation and utilization, and future opportunities are discussed. A systematic summary is started on three kinds of ambient electrochemically synthetic routes for SASs, including electrochemical etching (ECE), direct electrodeposition (DED), and electrochemical leaching-redeposition (ELR), associated with advanced characterization techniques. Next, their electrocatalytic applications for hydrogen energy conversion including hydrogen evolution reaction, oxygen evolution reaction, overall water splitting, and oxygen reduction reaction are reviewed. Finally, a brief conclusion and remarks on future challenges regarding further development of ambient electrosynthesis of high-performance and cost-effective SASCs for many other electrocatalytic applications are presented.

Band engineering in heterostructure catalysts to achieve High-Performance Lithium-Oxygen batteries

The electronic structure of cathode catalysts dominates the electrochemistry reaction kinetics in lithium-oxygen batteries. However, conventional catalysts perform inferior intrinsic activity due to the low d-band level of the active sites makes it difficult to bond with the reaction intermediates, which results in poor electrochemical performance of lithium-oxygen batteries. Herein, NiFe₂O₄/MoS₂ heterostructures are elaborately constructed to reach an electronic state balance for the active sites, which realizes the upper shift of the d-band level and enhanced adsorption of intermediates. Density functional theory calculation suggests that the d-band center of Fe active sites on the heterostructure moves toward the Fermi level, demonstrating the heterointerface engineering endows Fe active sites with high d-band level by the transfer and balance of electron. As a proof of concept, lithium-oxygen battery catalyzed by NiFe₂O₄/MoS₂ exhibits a large specific capacity of 21526 mA h g^-1 and an extended cycle performance for 268 cycles. Moreover, NiFe₂O₄/MoS₂ with strong adsorption to intermediates promotes the uniform growth of discharge products, which is favor of the reversible decomposition during cycling. This work presents the energy band regulation of the active sites in heterostructure catalysts has great feasibility for enhancing catalytic activities.

The built-in electric field across FeN/Fe3N interface for efficient electrochemical reduction of CO2 to CO

Nanostructured metal-nitrides have attracted tremendous interest as a new generation of catalysts for electroreduction of CO₂, but these structures have limited activity and stability in the reduction condition. Herein, we report a method of fabricating FeN/Fe₃N nanoparticles with FeN/Fe₃N interface exposed on the NP surface for efficient electrochemical CO₂ reduction reaction (CO₂RR). The FeN/Fe₃N interface is populated with Fe-N₄ and Fe-N₂ coordination sites respectively that show the desired catalysis synergy to enhance the reduction of CO₂ to CO. The CO Faraday efficiency reaches 98% at -0.4 V vs. reversible hydrogen electrode, and the FE stays stable from -0.4 to -0.9 V during the 100 h electrolysis time period. This FeN/Fe₃N synergy arises from electron transfer from Fe₃N to FeN and the preferred CO₂ adsorption and reduction to *COOH on FeN. Our study demonstrates a reliable interface control strategy to improve catalytic efficiency of the Fe-N structure for CO₂RR.

Single-Atom Pd-N4 Catalysis for Stable Low-Overpotential Lithium-Oxygen Battery

The critical challenge for Li-O₂ batteries lies in the large charge overpotential, leading to undesirable side reactions and inferior cycle stability. Single-atom catalysts have shown promising prospects in expediting the kinetics of oxygen evolution reaction (OER) for Li-O₂ batteries. However, a present practical drawback is the limited understanding of the correlation between the unique atomic structures and the OER mechanism. Herein, a template-assisted strategy is reported to synthesize atomically dispersed Pd anchored on N-doped carbon spheres as cathode catalysts. Benefiting from the well-defined Pd-N₄ moiety, the morphology and distribution of Li₂ O₂ products are distinctly regulated with optimized decomposition reversibility. Theoretical simulations reveal that the unique configuration of Pd-N₄ will contribute to the electron transfer from Pd atoms to the adjacent N atoms, which turns the originally electroneutral Pd into positively charged and downshifts the d-band center and therefore weakens its adsorption energy with the intermediates. The Li-O₂ batteries with Pd SAs/NC cathode achieve a charge overpotential of only 0.24 V and sustainable low-overpotential cycling stability (500 mA g^-1 ), and can retain a low charge voltage to a very high capacity of 10 000 mAh g^-1 . This work provides some insights into designing efficient single-atom catalysts for stable low-overpotential Li-O₂ batteries.

Engineering the Electronic Interaction between Atomically Dispersed Fe and RuO2 Attaining High Catalytic Activity and Durability Catalyst for Li-O2 Battery

It is significant to develop catalysts with high catalytic activity and durability to improve the electrochemical performances of lithium-oxygen batteries (LOBs). While electronic metal-support interaction (EMSI) between metal atoms and support has shown great potential in catalytic field. Hence, to effectively improve the electrochemical performance of LOBs, atomically dispersed Fe modified RuO2 nanoparticles are designed to be loaded on hierarchical porous carbon shells (FeSA -RuO2 /HPCS) based on EMSI criterion. It is revealed that the Ru-O-Fe1 structure is formed between the atomically dispersed Fe atoms and the surrounding Ru sites through electron interaction, and this structure could act as the ultra-high activity driving force center of oxygen reduction/evolution reaction (ORR/OER). Specifically, the Ru-O-Fe1 structure enhances the reaction kinetics of ORR to a certain extent, and optimizes the morphology of discharge products by reducing the adsorption energy of catalyst for O2 and LiO2 ; while during the OER process, the Ru-O-Fe1 structure not only greatly enhances the reaction kinetics of OER, but also catalyzes the efficient decomposition of the discharge products Li2 O2 by the favorable electron transfer between the active sites and the discharge products. Hence, LOBs based on FeSA-RuO2 /HPCS cathodes show an ultra-low over-potential, high discharge capacity and superior durability.

Covalent organic frameworks with Ni-Bis(dithiolene) and Co-porphyrin units as bifunctional catalysts for Li-O2 batteries

The rational design of efficient and stable catalysts for the oxygen reduction reaction and oxygen evolution reaction (ORR/OER) is the key to improving Li-O₂ battery performance. Here, we report the construction of ORR/OER bifunctional cathode catalysts in a covalent organic framework (COF) platform by simultaneously incorporating Ni-bis(dithiolene) and Co-porphyrin units. The resulting bimetallic Ni/Co-COF exhibits high surface area, fairly good electrical conductivity, and excellent chemical stability. Li-O₂ batteries with the Ni/Co-COF-based cathode show a low discharge/charge potential gap (1.0 V) and stable cycling (200 cycles) at a current density of 500 mA g^-1, rivaling that of PtAu nanocrystals. Density functional theory computations and control experiments using nonmetal or single metal-based isostructural COFs reveal the critical role of Ni and Co sites in reducing the discharge/charge overpotentials and regulating the Li₂O₂ deposition. This work highlights the advantage of bimetallic COFs in the rational design of efficient and stable Li-O₂ batteries.

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

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

Bifunctional Photoassisted Li-O2 Battery with Ultrahigh Rate-Cycling Performance Based on Siloxene Size Regulation

Directly integrating the bifunctional photoelectrode into Li-O2 batteries has been considered an effective way to reduce the overpotential and promote electric energy saving. However, more regular investigations on various bifunctional photocatalysts have still been desired for high-performance photoassisted Li-O2 batteries. Herein, a systematic exploration of various-sized siloxene photocatalysts affected by Li-O2 batteries has been introduced. Compared with the utilization of larger-sized siloxene nanosheets (SNSs), the photoassisted Li-O2 battery with a siloxene quantum dot (SQD) photoelectrode delivers a superior round-trip efficiency of 230% based on the highest discharge potential up to 3.72 V and lowest charge potential of 1.60 V and enables the maintenance of a long-term cycling life with only 13% efficiency attenuation after 200 cycles at 0.075 mA/cm2. Furthermore, this system exhibits a record-high rate-cycling performance (162% round-trip efficiency, even at 3 mA/cm2) and a high discharge capacity of 2212 mAh/g at 1 mA/cm2. These ground-breaking performances could be attributed to the synergistic effect of the photocatalytic and electrocatalytic activities of SQD photocatalysts with the ideal conduction band/valence band values, the abundant defective sites, and the stronger O2 and lower LiO2 adsorption strengths of SQD photocatalysts. These systematic research studies highlight the significance of SQD bifunctional photocatalysts and could be extended to other photocatalysts for further high-efficiency photoelectric conversion and storage.

Ultrafine Co-Species Interspersed g-C3N4 Nanosheets and Graphene as an Efficient Polysulfide Barrier to Enable High Performance Li-S Batteries

Lithium-sulfur (Li-S) batteries are regarded as one of the promising advanced energy storage systems due to their ultrahigh capacity and energy density. However, their practical applications are still hindered by the serious shuttle effect and sluggish reaction kinetics of soluble lithium polysulfides. Herein, g-C₃N₄ nanosheets and graphene decorated with an ultrafine Co-species nanodot heterostructure (Co@g-C₃N₄/G) as separator coatings were designed following a facile approach. Such an interlayer can not only enable effective polysulfide affinity through the physical barrier and chemical binding but also simultaneously have a catalytic effect on polysulfide conversion. Because of these superior merits, the Li-S cells assembled with Co@g-C₃N₄/G-PP separators matched with the S/KB composites (up to ~70 wt% sulfur in the final cathode) exhibit excellent rate capability and good cyclic stability. A high specific capacity of ~860 mAh g^-1 at 2.0 C as well as a capacity-fading rate of only ~0.035% per cycle over 350 cycles at 0.5 C can be achieved. This bifunctional separator can even endow a Li-S cell at a low current density to exhibit excellent cycling capability, with a capacity retention rate of ~88.4% at 0.2 C over 250 cycles. Furthermore, a Li-S cell with a Co@g-C₃N₄/G-PP separator possesses a stable specific capacity of 785 mAh g^-1 at 0.2 C after 150 cycles and a superior capacity retention rate of ~84.6% with a high sulfur loading of ~3.0 mg cm^-2. This effective polysulfide-confined separator holds good promise for promoting the further development of high-energy-density Li-S batteries.

Single cobalt atom anchored on carbon nitride with cobalt nitrogen/oxygen active sites for efficient Fenton-like catalysis

As one of the tactics to produce reactive oxygen radicals, the Fenton-like process has been widely developed to solve the increasingly severe problem of environmental pollution. However, establishing advanced mediators with sufficient stability and activity for practical application is still a long-term objective. Herein, we proposed a facile strategy through polymeric carbon nitride (pCN) in-situ growth single cobalt atom for efficient degradation of antibiotics by peroxymonosulfate (PMS) activation. X-ray absorption spectroscopy and high-angle annular dark field-scanning transmission electron microscopy prove the single cobalt atoms are successfully anchored on pCN. Moreover, extended X-ray absorption fine structure analysis shows that the embedded cobalt atoms are constructed by covalently forming the Co-N bond and Co-O bond, which endow the single-atom cobalt catalyst with high stability. Experiment results indicate that the prepared single-atom cobalt catalyst can be used for efficient PMS activation catalytic degradation of tetracycline with a high degradation rate of 98.7 % in 60 min. And the CoN/O sites with single cobalt atoms serve as the active site for generating active radical species (singlet oxygen) from PMS activation. This work may expand the strategy for constructing single-atom catalysts and extend its application for the advanced oxidation process.

Interfacial Engineering of Co3 O4 /Fe2 O3 Nano-Heterostructure Toward Superior Li-O2 Batteries

A major issue with Li-O₂ batteries is their slow oxygen reduction and evolution kinetics, necessitating catalysts with high catalytic activity to improve reaction kinetics and cycle stability. Herein, a nano-heterostructured catalyst composed of Co₃ O₄ and Fe₂ O₃ (Co₃ O₄ /Fe₂ O₃ ) with a porous rod morphology is achieved through an interfacial engineering strategy by constructing Fe₂ O₃ on the Co₃ O₄ surface, which can function as a high-performance cathode in order to efficiently encourage the oxygen reduction and evolution while also reduce the battery polarization during charging and discharging. The density functional theory (DFT) calculations show the differences in charge density at the interface of nano-heterostructures, demonstrating the occurrence of an electron transfer process in the interface region of Co₃ O₄ and Fe₂ O₃ , implying a strong electronic coupling transfer, and in turn changing the electronic structure of the Co₃ O₄ . This significantly reduces the adsorption energy of LiO₂ intermediates, thereby effectively lowering the overpotential. The resultant Li-O₂ battery has larger discharge specific capacity, lower overpotential for the efficient oxygen evolution/reduction, as well as good cycling stability of 280 cycles. This work demonstrates an effective method to fabricate the nano-heterostrucutred materials with enhanced catalytic efficiency for advanced energy applications.

Light-Assisted Metal-Air Batteries: Progress, Challenges, and Perspectives

Metal-air batteries are considered one of the most promising next-generation energy storage devices owing to their ultrahigh theoretical specific energy. However, sluggish cathode kinetics (O₂ and CO₂ reduction/evolution) result in large overpotentials and low round-trip efficiencies which seriously hinder their practical applications. Utilizing light to drive slow cathode processes has increasingly becoming a promising solution to this issue. Considering the rapid development and emerging issues of this field, this Review summarizes the current understanding of light-assisted metal-air batteries in terms of configurations and mechanisms, provides general design strategies and specific examples of photocathodes, systematically discusses the influence of light on batteries, and finally identifies existing gaps and future priorities for the development of practical light-assisted metal-air batteries.

Edge-hosted Atomic Co-N4 Sites on Hierarchical Porous Carbon for Highly Selective Two-electron Oxygen Reduction Reaction

Not only high efficiency but also high selectivity of the electrocatalysts is crucial for high-performance, low-cost, and sustainable energy storage applications. Herein, we systematically investigate the edge effect of carbon-supported single-atom catalysts (SACs) on oxygen reduction reaction (ORR) pathways (two-electron (2 e^- ) or four-electron (4 e^- )) and conclude that the 2 e^- -ORR proceeding over the edge-hosted atomic Co-N₄ sites is more favorable than the basal-plane-hosted ones. As such, we have successfully synthesized and tuned Co-SACs with different edge-to-bulk ratios. The as-prepared edge-rich Co-N/HPC catalyst exhibits excellent 2 e^- -ORR performance with a remarkable selectivity of ≈95 % in a wide potential range. Furthermore, we also find that oxygen functional groups could saturate the graphitic carbon edges under the ORR operation and further promote electrocatalytic performance. These findings on the structure-property relationship in SACs offer a promising direction for large-scale and low-cost electrochemical H₂ O₂ production via the 2 e^- -ORR.

A first-principles study on atomic-scale pore design of microporous carbon electrodes for lithium-ion batteries

Porous carbon materials are considered attractive lithium storage media because their large specific surface areas and pore volumes provide high adsorption capacity. This first-principles study elucidates the atomic-scale mechanisms of lithium storage and diffusion in microporous carbon. Microporous carbon structures with initial densities of 1.5, 2.0, and 2.5 g cm-3 store up to 7.5-8.2 Li ions per C6 corresponding to the capacities of 2783-3032 mA h g-1, which are 7-8 times higher than that for graphite. Fully lithiated microporous carbon has about 62% of Li ions inside the pore cavity and on the pore surface, responsible for reversible capacity, and about 38% of Li ions inside the pore wall, responsible for irreversible capacity. As lithiation proceeds, microporous carbon structures with different total pore volumes evolve to have similar total pore volumes but different average pore volumes. The average pore volume has a great influence on Li ion conductivity, as evidenced by the highest conductivity of 103.5 mS cm-1 for the largest average pore diameter of 9.3 Å. Inside large pore cavities, Li ions diffuse rapidly without encountering carbon atoms that impede Li diffusion, suggesting that a high Li-to-C ratio around Li causes fast Li ion motion. This study offers not only a comprehensive understanding of the lithiation of microporous carbon but also design directions for developing efficient microporous carbon electrodes for lithium-ion batteries.

Highly Dispersed Ru-Co Nanoparticles Interfaced With Nitrogen-Doped Carbon Polyhedron for High Efficiency Reversible Li-O2 Battery

The lithium-oxygen (Li-O₂ ) battery with high energy density of 3860 Wh kg^-1 represents one of the most promising new secondary batteries for future electric vehicles and mobile electronic devices. However, slow oxygen reduction/oxygen evolution (ORR/OER) reaction efficiency and unstable cycling performance restrain the practical applications of the Li-O₂ battery. Herein, Ru-modified nitrogen-doped porous carbon-encapsulated Co nanoparticles (Ru/Co@CoN_x -C) are synthesized through reduction of Ru on metal-organic framework (MOFs) pyrolyzed derivatives strategies. Porous carbon polyhedra provide channels for reactive species and stable structure ensures the cyclic stability of the catalyst; abundant Co-N_x sites and high specific surface area (353 m² g^-1 ) provide more catalytically active sites and deposition sites for reaction products. Theoretical calculations further verify that Ru/Co@CoN_x -C can regulate the growth of Li₂ O₂ to improve reversibility of Li-O₂ batteries. Li-O₂ batteries with Ru/Co@CoN_x -C as cathode catalyst achieve small voltage gaps of 1.08 V, exhibit excellent cycle stability (205 cycles), and deliver high discharge specific capacity (17050 mAh g^-1 ). Furthermore, pouch-type Li-O₂ batteries that maintain stable electrochemical performance output even under conditions of bending deformation and corner cutting are successfully assembled. This study demonstrates Ru/Co@CoN_x -C catalyst's great application potential in Li-O₂ batteries.

Hydrogenolysis of Polyethylene and Polypropylene into Propane over Cobalt-Based Catalysts

The development of technologies to recycle polyethylene (PE) and polypropylene (PP), globally the two most produced polymers, is critical to increase plastic circularity. Here, we show that 5 wt % cobalt supported on ZSM-5 zeolite catalyzes the solvent-free hydrogenolysis of PE and PP into propane with weight-based selectivity in the gas phase over 80 wt % after 20 h at 523 K and 40 bar H2. This catalyst significantly reduces the formation of undesired CH4 (≤5 wt %), a product which is favored when using bulk cobalt oxide or cobalt nanoparticles supported on other carriers (selectivity ≤95 wt %). The superior performance of Co/ZSM-5 is attributed to the stabilization of dispersed oxidic cobalt nanoparticles by the zeolite support, preventing further reduction to metallic species that appear to catalyze CH4 generation. While ZSM-5 is also active for propane formation at 523 K, the presence of Co promotes stability and selectivity. After optimizing the metal loading, it was demonstrated that 10 wt % Co/ZSM-5 can selectively catalyze the hydrogenolysis of low-density PE (LDPE), mixtures of LDPE and PP, as well as postconsumer PE, showcasing the effectiveness of this technology to upcycle realistic plastic waste. Cobalt supported on zeolites FAU, MOR, and BEA were also effective catalysts for C2-C4 hydrocarbon formation and revealed that the framework topology provides a handle to tune gas-phase selectivity.