Addressing adsorption and catalysis of lithium polysulfide via electronic distribution of molybdenum carbide host.

Heterostructure engineering is considered a crucial strategy to modulate the intrinsic charge transfer behavior of materials, enhance catalytic activity, and optimize sulfur electrochemical processes. However, parsing the role of heterogeneous interface-structure-property relationships in heterostructures is still a key scientific issue to realize the efficient catalytic conversion of polysulfides. Based on this, molybdenum carbide (Mo2C) was successfully partial reduced to molybdenum metal (Mo) via a thermal reduction at high-temperature and the typical Mo-Mo2C-based Mott-Schottky heterostructures were simultaneously constructed, which realized the modulation of the electronic structure of Mo2C and optimized the conversion process of lithium polysulfides (LPS). Compared with single molybdenum carbide, the modulated molybdenum carbide acts as an electron donor with stronger Mo-S bonding strength as well as higher polysulfide adsorption energy, faster Li2S conversion kinetics, and greatly facilitates the adsorption → catalysis process of LPS. As a result, yolk-shell Mo-Mo2C heterostructure (C@Mo-Mo2C) exhibits excellent cycling performance as a sulfur host, with a discharge specific capacity of 488.41 mAh g-1 for C@Mo-Mo2C/S at 4 C and present an excellent high-rate cyclic performance accompanied by capacity decay rate of 0.08 % per cycle after 400 cycles at 2 C. Heterostructure-acting Mo2C electron distribution modulation engineering may contributes to the understanding of the structure-interface-property interaction law in heterostructures and further enables the efficient modulation of the chemical behavior of sulfur.

Key Roles of Interfaces in Inverted Metal-Halide Perovskite Solar Cells.

Metal-halide perovskite solar cells (PSCs), an emerging technology for transforming solar energy into a clean source of electricity, have reached efficiency levels comparable to those of commercial silicon cells. Compared with other types of PSCs, inverted perovskite solar cells (IPSCs) have shown promise with regard to commercialization due to their facile fabrication and excellent optoelectronic properties. The interlayer interfaces play an important role in the performance of perovskite cells, not only affecting charge transfer and transport, but also acting as a barrier against oxygen and moisture permeation. Herein, we describe and summarize the last three years of studies that summarize the advantages of interface engineering-based advances for the commercialization of IPSCs. This review includes a brief introduction of the structure and working principle of IPSCs, and analyzes how interfaces affect the performance of IPSC devices from the perspective of photovoltaic performance and device lifetime. In addition, a comprehensive summary of various interface engineering approaches to solving these problems and challenges in IPSCs, including the use of interlayers, interface modification, defect passivation, and others, is summarized. Moreover, based upon current developments and breakthroughs, fundamental and engineering perspectives on future commercialization pathways are provided for the innovation and design of next-generation IPSCs.

Interlayer Entropy Engineering Inducing the Symmetry-Broken Layered Oxide Cathodes to Activate Reversible High-Voltage Redox Reaction.

The as-reported doping entropy engineering of electrode materials that are usually realized by the sharing of multiple metal elements with the metal element from the lattice body, potentially has three shortages of stringent synthesis conditions, large active element loss, and serious lattice distortion. Herein, an interlayer entropy engineering of layered oxide cathodes is proposed, where the multiple metal ions are simultaneously intercalated into the same interlayer sites, thus avoiding the three shortages. Concretely, a novel interlayer medium-entropy V2O5 ((MnCoNiMgZn)0.26V2O5∙0.84H2O) is successfully constructed by a one-step hydrothermal method. The interlayer medium-entropy effect is revealed to be that five metal ions pre-intercalation induces the local symmetry-broken [VO6] octahedra in bilayer V2O5, thus activating the reversible high-voltage redox reaction, inhibiting the layer slip and following phase transformation by its pinning effect, and enhancing the charge transfer kinetics. As a result, the medium-entropy cathode realizes the trade-off between specific capacity and structural stability with a discharge capacity of 152 mAh g-1 at 0.1 A g-1 after 100 cycles, and a capacity retention rate of 98.7% at 0.5 A g-1 after 150 cycles for Li+ storage. This engineering provides a new guideline for the rational design of high-performance layered oxide cathodes.

RhNi Bimetallenes with Lattice-Compressed Rh Skin towards Ultrastable Acidic Nitrate Electroreduction.

Harvesting recyclable ammonia (NH3 ) from acidic nitrate (NO3 - )-containing wastewater requires the utilization of corrosion-resistant electrocatalytic materials with high activity and selectivity towards acidic electrochemical nitrate reduction (NO3 ER). Herein, ultrathin RhNi bimetallenes with Rh-skin-type structure (RhNi@Rh BMLs) are fabricated towards acidic NO3 ER. The Rh-skin atoms on the surface of RhNi@Rh BMLs experience the lattice compression-induced strain effect, resulting in shortened Rh-Rh bond and downshifted d-band center. Experimental and theoretical calculation results corroborate that Rh-skin atoms can inhibit NO2 */NH2 * adsorption-induced Rh dissolution, contributing to the exceptional electrocatalytic durability of RhNi@Rh BMLs (over 400 h) towards acidic NO3 ER. RhNi@Rh BMLs also reveal an excellent catalytic performance, boasting a 98.4% NH3 Faradaic efficiency and a 13.4 mg h-1 mgcat -1 NH3 yield. Theoretical calculations reveal that compressive stress tunes the electronic structure of Rh skin atoms, which facilitates the reduction of NO* to NOH* in NO3 ER. The practicality of RhNi@Rh BMLs has also been confirmed in an alkaline-acidic hybrid zinc-nitrate battery with a 1.39 V open circuit voltage and a 10.5 mW cm-2 power density. This work offers valuable insights into the nature of electrocatalyst deactivation behavior and guides the development of high-efficiency corrosion-resistant electrocatalysts for applications in energy and environment.

Tuning Redox Behavior of Sulfur Cathodes Via Ternary-Coordinated Single Fe Atom in Lithium-Sulfur Batteries.

Modulating the coordination configuration of single Fe atom has been an efficient strategy to strengthen the redox dynamics for lithium-sulfur batteries (LSBs) but remains challenging. Herein, the single Fe atom is functioned with nitrogen and carbon atoms in the first shell, and simultaneously, oxidized sulfur (─SOx) in the second shell, which presents a lower antibonding state and well address the redox activity of sulfur cathodes. In the ternary-coordinated single Fe atom catalyst (FeN2 C2 -SOx-NC), the binary structure of FeN2 C2 provides a lower Fe-S bonding strength and d-p orbital hybridization, which obviously optimizes the adsorption and desorption behavior of sulfur species during the reduction and oxidation reaction processes. Simultaneously, the ─SOx redistributes the electron density of the coordinating nitrogen atoms, which possesses high electron-withdrawing ability and develops electrocatalytic activity. As a result, the sulfur cathodes with FeN2 C2 -SOx-NC present an excellent high-rate cyclic performance, accompanied by a capacity decay rate of 0.08% per cycle for 500 cycles at 4.0 C. This study provides new insights for optimizing the redox dynamics of sulfur cathodes in LSBs at the atomic level.

A Review on Engineering Transition Metal Compound Catalysts to Accelerate the Redox Kinetics of Sulfur Cathodes for Lithium-Sulfur Batteries.

Engineering transition metal compounds (TMCs) catalysts with excellent adsorption-catalytic ability has been one of the most effective strategies to accelerate the redox kinetics of sulfur cathodes. Herein, this review focuses on engineering TMCs catalysts by cation doping/anion doping/dual doping, bimetallic/bi-anionic TMCs, and TMCs-based heterostructure composites. It is obvious that introducing cations/anions to TMCs or constructing heterostructure can boost adsorption-catalytic capacity by regulating the electronic structure including energy band, d/p-band center, electron filling, and valence state. Moreover, the electronic structure of doped/dual-ionic TMCs are adjusted by inducing ions with different electronegativity, electron filling, and ion radius, resulting in electron redistribution, bonds reconstruction, induced vacancies due to the electronic interaction and changed crystal structure such as lattice spacing and lattice distortion. Different from the aforementioned two strategies, heterostructures are constructed by two types of TMCs with different Fermi energy levels, which causes built-in electric field and electrons transfer through the interface, and induces electron redistribution and arranged local atoms to regulate the electronic structure. Additionally, the lacking studies of the three strategies to comprehensively regulate electronic structure for improving catalytic performance are pointed out. It is believed that this review can guide the design of advanced TMCs catalysts for boosting redox of lithium sulfur batteries.

Bimetallic-MOF Derived Carbon with Single Pt Anchored C4 Atomic Group Constructing Super Fuel Cell with Ultrahigh Power Density And Self-Change Ability.

Pursuing high power density with low platinum catalysts loading is a huge challenge for developing high-performance fuel cells (FCs). Herein, a new super fuel cell (SFC) is proposed with ultrahigh output power via specific electric double-layer capacitance (EDLC) + oxygen reduction reaction (ORR) parallel discharge, which is achieved using the newly prepared catalyst, single-atomic platinum on bimetallic metal-organic framework (MOF)-derived hollow porous carbon nanorods (PtSA /HPCNR). The PtSA-1.74 /HPCNR-based SFC has a 3.4-time higher transient specific power density and 13.3-time longer discharge time with unique in situ self-charge and energy storage ability than 20% Pt/C-based FCs. X-ray absorption fine structure, aberration-corrected high-angle annular dark-field scanning transmission electron microscope, and density functional theory calculations demonstrate that the synergistic effect of Pt single-atoms anchored on carbon defects significantly boosts its electron transfer, ORR catalytic activity, durability, and rate performance, realizing rapid " ORR+EDLC" parallel discharge mechanism to overcome the sluggish ORR process of traditional FCs. The promising SFC leads to a new pathway to boost the power density of FCs with extra-low Pt loading.

Proton Intercalation/De-intercalation Chemistry in Phenazine-based Anode for Hydronium-ion Batteries.

Hydronium-ion batteries have received significant attention owing to the merits of extraordinary sustainability and excellent rate abilities. However, achieving high-performance hydronium-ion batteries remains a challenge due to the inferior properties of anode materials in strong acid electrolyte. Herein, a hydronium-ion battery is constructed which is based on a diquinoxalino [2,3-a:2',3'-c] phenazine (HATN) anode and a MnO2 @graphite felt cathode in a hybrid acidic electrolyte. The fast kinetics of hydronium-ion insertion/extraction into HATN electrode endows the HATN//MnO2 @GF battery with enhanced electrochemical performance. This battery exhibits an excellent rate performance (266 mAh g-1 at 0.5 A g-1 , 97 mAh g-1 at 50 A g-1 ), attractive energy density (182.1 Wh kg-1 ) and power density (31.2 kW kg-1 ), along with long-term cycle stability. These results shed light on the development of advanced hydronium-ion batteries.

Graphitized Carbon-Coated Iron Fluoride Nanocavities for Enhanced Kinetics of Multielectron Cathode Conversion Reactions.

As for the conversion-type iron fluoride (FeF3) cathode material with multielectron reactions for lithium-ion batteries (LIBs), sluggish reaction kinetics and low electrical conductivity pose certain limitations for the long-lasting reversible conversion processes. Herein, the three-dimensional porous nitrogen-doped carbon matrix in situ anchoring FeF3 nanocavities coated by graphitized carbon (FeF3/GC) are rationally prepared. Through the Kirkendall effect, the low-temperature fluorination of NF3 enables the resultant hollow FeF3 nanoparticles to possess a large number of lithium storage cavities and outer graphitized carbon structure, further effectively buffering the expansion of volume. The FeF3/GC cathode delivers a superior discharge capacity of 504.2 mAh g-1 after 1200 cycles at 1000 mA g-1, with a capacity decay rate of only 0.01% per cycle. Even at a rate of 5000 mA g-1, the composite cathode still delivers a discharge capacity of 309.6 mAh g-1. Impressively, the existence of graphitized carbon and the short Li+ diffusion length ensure fast electron/ion transfer, which significantly enhances the conversion reaction kinetics. This study aims to provide a promising strategy for the efficiency enhancement of multielectron cathode conversion reactions for LIBs.

Oxygen vacancies in MnOx regulating reaction kinetics for aqueous zinc-ion batteries.

MnO2 cathode materials have presented challenges due to their poor conductivity, unstable structure, and sluggish diffusion kinetics for aqueous zinc-ion batteries (AZIBs). In this study, a nanostructured MnOx cathode material was synthesized using an acid etching method, Which introduced abundant Mn(III) sites, resulting in the formation of numerous oxygen vacancies. Comprehensive characterizations revealed that these oxygen vacancies facilitated the reversible adsorption/desorption of Zn2+ ions and promoted efficient electron transfer. In addition, the designed mesoporous structure offered ample active sites and shortened the diffusion path for Zn2+ and H+ ions. Consequently, the nanosized MnOx cathode exhibited enhanced reaction kinetics, achieving a considerable reversible specific capacity of 388.7 mAh/g at 0.1 A/g and superior durability with 72.0% capacity retention over 2000 cycles at 3.0 A/g. The material delivered a maximum energy density of 639.7 Wh kg-1 at 159.94 W kg-1. Furthermore, a systematic analysis of the zinc storage mechanism was performed. This work demonstrates that engineering oxygen vacancies with nanostructure regulation provides valuable insights into optimizing MnO2 cathode materials for AZIBs.

Fabrication of a flexible porous polypyrrole film with a 3D micro-nanostructure and its electrochemical properties.

Flexible energy storage systems have become attractive alternatives for applications in wearable energy storage and sensor devices. This study reports a simple electro-polymerization method for the fabrication of PPy films coated on PPy nanotubes (PPy NTs), which are binding-free, self-standing, and could be used as a flexible electrode for supercapacitors. With optimized kinetics for ion transportation, the mass specific capacitance of the flexible porous PPy films can be elevated to 1.36 F cm-2 at a charging/discharging rate of 2 mA cm-2 (0.45 A g-1). The mass specific capacitance of the flexible porous PPy films reaches 6.5 times as large as that of compact PPy films at a scan rate of 20 mV s-1. Furthermore, due to the large free space for volume change, the capacitance fading of the flexible porous PPy films is less than 3% after 10 000 cycles. This novel design provides an efficient method to synthesize high-performance, flexible and low-cost materials used in supercapacitors.

Intelligent Chip-Controlled Smart Oxygen Electrodes for Constructing Rechargeable Zinc-Air Batteries with Excellent Energy Efficiency and Durability.

High-performance rechargeable oxygen electrodes are key devices for realizing high-specific-energy batteries, including zinc-air and lithium-air batteries. However, these batteries have severe problems of premature decay in energy efficiency by serious corrosion, wide charge-discharge gap, and catalyst peeling off. Herein, we propose a "smart dual-oxygen electrode", which is composed of an intelligent switch control module + heterostructured Fe1Ni3-LDH/PNCNF OER catalysis electrode layer + ion conductive | electronic insulating membrane + Pt/C ORR catalysis electrode layer, where OER and ORR layers are automatically switched by the intelligent switch control module as required. This smart dual-oxygen electrode offers an ultralow energy efficiency decay rate of 0.0067% after 300 cycles during cycling, much lower than that of the commercial Pt/C electrode (1.82%). The assembled rechargeable zinc-air battery (RZAB) displays a super narrow voltage gap and achieves a high energy efficiency of 71.7%, far higher than that of the existing RZABs (about 50%). Therefore, this strategy provides a complete solution for designing various high-performance metal-air secondary batteries.

Hybrid Nano-Phase Ion/Electron Dual Pathways of Nickel/Cobalt-Boride Cathodes Boosting Intercalation Kinetics for Alkaline Batteries.

Nickel-based hydroxides and their derivatives exhibit relatively low capacities and unsatisfactory durability as cathode materials for rechargeable alkaline batteries. In this work, a hybrid NiCo-B nanosheet cathode, integrating electrolyte ion-shuttling channels and electron-transferring networks into a metal-organic framework (MOF), was devised delicately. In the structure, the hybrid ion/electron dual pathways were constructed by NiCo-MOF frameworks and NiCo-B interpenetration networks. It revealed that nano-phase electron-transferring pathways in the MOF obviously boosted ion intercalation kinetics. The as-obtained hybrid NiCo-B nanosheets as cathode materials exhibited reversible capacity as high as 280 mA h g-1 at a current density of 1 A g-1 and excellent rate capability with a capacity retention of 78% from 1 to 10 A g-1. After 2000 charge/discharge cycles at 4 A g-1, the capacity still remained at 94% of the initial one. A full battery assembled with a hybrid NiCo-B cathode and a Fe2O3 anode showed a high capacity of 250 mA h g-1 and a considerable stability of 89% after 1000 cycles. Ragone plots indicated the highest energy density of 409 W h kg-1 and the lowest power density of 1.5 kW kg-1, outperforming other aqueous batteries. It revealed that a syngenetic structure of ion/electron hybrid dual pathways integrated into an MOF could be a potential strategy to optimize ion intercalation electrode materials for alkaline batteries.

Engineering p-Band Center of Oxygen Boosting H+ Intercalation in δ-MnO2 for Aqueous Zinc Ion Batteries.

In aqueous zinc ion batteries (ZIBs), the H+ intercalation possesses superior electrochemical kinetics with excellent rate capability, however, precisely modulating H+ intercalation has been still challenging. Herein, a critical modification of pre-intercalating metal ions in the MnO2 interlayer (M-MnO2 ) with controllable p-band center (ϵp ) of O is reported to modulate the H+ intercalation. The modulation of metal-O bond type and covalency degree on the average charge of O atom results in optimized ϵp and H+ adsorption energy for M-MnO2 , thus promoting the balance between H+ adsorption and desorption, which plays a determinant role on H+ intercalation. The optimized Cu-MnO2 delivers superior rate capability with the capacity of 153 mAh g-1 at a high rate of 3 A g-1 after 1000 cycles. This work demonstrates that ϵp could be a significant descriptor for H+ intercalation, and tuning ϵp effectively increases H+ intercalation contribution with excellent rate capability in ZIBs.

Crystal phase engineering of nanoflower-like hollow MoSe2boosting polysulfide conversion for lithium-sulfur batteries.

The battery performance of sulfur cathode has obviously depended on the redox reaction kinetics of polysulfides upon cycling. Herein, an effective strategy was proposed to achieve the conversion from 2H (semiconductor phase) to 1T (metal phase) in hollow nano-flowered molybdenum selenide sphere (HFSMS) through crystal phase engineering. The HFSMS with different phase ratio was realized by regulating the proportion of reducing agents. Specifically, the 1T phase content can reach up to 60.8%, and then subsequently decreased to 59.1% with the further increase of the reducing agent. The as-prepared HFSMS with the 1T phase content of 60.8% showed a smallest Tafel slopes (49.99 and 79.65 mV/dec in reduction and oxidation process, respectively), fastest response time and highest response current (520 s, 0.459 mA in Li2S deposition test), which further exhibited excellent catalytic activity and faster reaction kinetics. This result was verified by electrochemical performance, which manifested as stable cycle life with only 0.112% capacity decay per cycle. It was found that the hollow structure can ensures a rich sulfur storage space, and effectually buffer the volume changes of the active substance. More importantly, the improved performance is attributed to the introduction of the 1T phase, which significantly improves the catalytic activity of MoSe2with promoting the polysulfide conversion.

Manipulating Charge-Transfer Kinetics of Lithium-Rich Layered Oxide Cathodes in Halide All-Solid-State Batteries.

Employing lithium-rich layered oxide (LLO) as the cathode of all-solid-state batteries (ASSBs) is highly desired for realizing high energy density. However, the poor kinetics of LLO, caused by its low electronic conductivity and significant oxygen-redox-induced structural degradation, has impeded its application in ASSBs. Here, the charge transfer kinetics of LLO is enhanced by constructing high-efficiency electron transport networks within solid-state electrodes, which considerably minimizes electron transfer resistance. In addition, an infusion-plus-coating strategy is introduced to stabilize the lattice oxygen of LLO, successfully suppressing the interfacial oxidation of solid electrolyte (Li3 InCl6 ) and structural degradation of LLO. As a result, LLO-based ASSBs exhibit a high discharge capacity of 230.7 mAh g-1 at 0.1 C and ultra-long cycle stability over 400 cycles. This work provides an in-depth understanding of the kinetics of LLO in solid-state electrodes, and affords a practically feasible strategy to obtain high-energy-density ASSBs.

A Rising 2D Star: Novel MBenes with Excellent Performance in Energy Conversion and Storage.

As a flourishing member of the two-dimensional (2D) nanomaterial family, MXenes have shown great potential in various research areas. In recent years, the continued growth of interest in MXene derivatives, 2D transition metal borides (MBenes), has contributed to the emergence of this 2D material as a latecomer. Due to the excellent electrical conductivity, mechanical properties and electrical properties, thus MBenes attract more researchers' interest. Extensive experimental and theoretical studies have shown that they have exciting energy conversion and electrochemical storage potential. However, a comprehensive and systematic review of MBenes applications has not been available so far. For this reason, we present a comprehensive summary of recent advances in MBenes research. We started by summarizing the latest fabrication routes and excellent properties of MBenes. The focus will then turn to their exciting potential for energy storage and conversion. Finally, a brief summary of the challenges and opportunities for MBenes in future practical applications is presented.

Improved rate performance of nanoscale cross-linked polyacrylonitrile-surface-modified LiNi0.8Co0.1Mn0.1O2 lithium-ion cathode material with ion and electron transmission channels.

LiNi0.8Co0.1Mn0.1O2 (NCM811) has attracted extensive attention due to its high energy density. Particularly, the Li-Ni mixing phenomenon and interfacial side reactions contribute to the rate and cycling performance of NCM811. Cross-linked polyacrylonitrile (cPAN) has certain electrical conductivity and is considered a competitive coating material. In this study, NCM811@cPAN was successfully prepared by wet chemical and heat treatments. The formation process of cPAN systematically analyzed by physical structure tests and microscopic morphological analysis demonstrates that cPAN existed on the surface of NCM811. The electrochemical results demonstrate that NCM811@cPAN has high initial coulombic efficiency (98.14% at 0.1C), good cycle stability and rate performance (222.30 mA h g-1 at 0.5C). The uniform and continuous nano cPAN coating helped avoid direct contact between NCM811 and the electrolyte, enhancing its interfacial stability. Moreover, cPAN exhibited certain electronic conductivity and generated a spinel structure, enhancing the diffusion rate of e- and Li+. Therefore, the electrochemical performance of NCM811 can be improved. This method and the coating material provide an effective strategy for the surface modification of other cathode materials used in Li-ion batteries.

Emerging Applications of Synchrotron Radiation X-Ray Techniques in Single Atomic Catalysts.

Single atom catalysts (SACs) can achieve a maximum atom utilization efficiency of 100%, which provides significantly increased active sites compared with traditional catalysts during catalytic reactions. Synchrotron radiation technology is an important characterization method for identifying single-atom catalysts. Several types of internal information, such as the coordination number, bond length and electronic structure of metals, can all be analyzed. This review will focus on the introduction of synchrotron radiation techniques and their applications in SACs. First, the fundamentals of synchrotron radiation and the corresponding techniques applied in characterization of SACs will be briefly introduced, such as X-ray absorption near edge spectroscopy and extended X-ray absorption fine structure spectroscopy and in situ techniques. The detailed information obtained from synchrotron radiation X-ray characterization is described through four routes: 1) the local environment of a specific atom; 2) the oxidation state of SACs; 3) electronic structures at different orbitals; and 4) the in situ structure modification during catalytic reaction. In addition, a systematic summary of synchrotron radiation X-ray characterization on different types of SACs (noble metals and transition metals) will be discussed.

In-MOF-Derived Hierarchically Hollow Carbon Nanostraws for Advanced Zinc-Iodine Batteries.

Hollow carbon materials are regarded as crucial support materials in catalysis and electrochemical energy storage on account of their unique porous structure and electrical properties. Herein, an indium-based organic framework of InOF-1 can be thermally carbonized under inert argon to form indium particles through the redox reaction between nanosized indium oxide and carbon matrix. In particular, a type of porous hollow carbon nanostraw (HCNS) is in situ obtained by combining the fusion and removal of indium within the decarboxylation process. The as-synthesized HCNS, which possesses more charge active sites, short and quick electron, and ion transport pathways, has become an excellent carrier for electrochemically active species such as iodine with its unique internal cavity and interconnected porous structure on the tube wall. Furthermore, the assembled zinc-iodine batteries (ZIBs) provide a high capacity of 234.1 mAh g-1 at 1 A g-1 , which ensures that the adsorption and dissolution of iodine species in the electrolyte reach a rapid equilibrium. The rate and cycle performance of the HCNS-based ZIBs are greatly improved, thereby exhibiting an excellent capacity retention rate. It shows a better electrochemical exchange capacity than typical unidirectional carbon nanotubes, making HCNS an ideal cathode material for a new generation of high-performance batteries.