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A heterostructure of defect-rich isomorphic pyrite CoSe0.5S1.5nanoparticles embedded in porous conducting matrix (CoSe0.5S1.5/GA) composite is fabricated and possesses excellent electrochemical properties as a high-performance sodium ion capacitors anode.

Layered double hydroxides (LDHs) have been intensively investigated as promising cathodes for the new concept chloride ion battery (CIB) with multiple advantages of high theoretical energy density, abundant raw materials and unique dendrite-free characteristics. However, driven by the great compositional diversity, a complete understanding of interactions between metal cations, as well as a synergetic effect between metal cations and lattice oxygen on LDH host layers in terms of the reversible Cl-storage capability, is still a crucial but elusive issue. In this work, we synthesized a series of chloride-inserted trinary Mox-doped NiCo2-Cl LDH (x= 0, 0.1, 0.2, 0.3, 0.4, and 0.5) with gradient oxygen vacancies as enhanced cathodes toward CIBs. The combination of advanced spectroscopic techniques and theoretical calculations reveals that the Mo dopant facilitates oxygen vacancy formation and varies the valence states of coordinated transition metals, which can not only tune the electronic structure effectively and promote Cl-ion diffusion, but improve the redox activity of LDHs. The optimized Mo0.3NiCo2-Cl LDH delivers a reversible discharge capacity of 159.7 mA h g−1after 300 cycles at 150 mA g−1, which is almost a triple enhancement compared to that of NiCo2Cl LDH. The superior Cl-storage of trinary Mo0.3NiCo2Cl LDH is attributed to the reversible intercalation/deintercalation of chloride ions in the LDH gallery along with the oxidation state changes in Ni0/Ni2+/Ni3+, Co0/Co2+/Co3+and Mo4+/Mo6+couples. This simple vacancy engineering strategy provides critical insights into the significance of the chemical interaction of various components on LDH laminates and aims to effectively design more LDH-based cathodes for CIBs, which can even be extended to other halide-ion batteries like fluoride ion batteries and bromide ion batteries.

Owing to the distinctive and designable properties of high-entropy alloys (HEAs), many researchers have been engrossed in studying them. The CrFeNiNbx(xis the molar ratio; x= 0.4, 0.5, 0.6, 0.7, 0.8) alloys were prepared using vacuum arc melting furnace equipment to study the impact of Nb content on microstructure, processing performance, and corrosion resistance. Laves primary phase and eutectic structure phase were obtained. And the area of the Laves primary structure, which was rich in Nb, was amplified when the alloy's percentage of Nb was supplemented. The Nb4 alloy (x= 0.4) exhibited a range of satisfactory mechanical properties, including a hardness of 422.3 HV, a compressive stress of 2355 MPa, and a compressive strain of 26.33%. Cracks formed around the Laves phase during electrochemical corrosion experimentation, and the alloy passivation film's breakdown potential was approximately 1.0 V.

Solar-driven nitrogen fixation is a promising clean and mild approach for ammonia synthesis beyond the conventional energy-intensive Haber–Bosch process. However, it is still challenging to design highly active, stable, and low-cost photocatalysts for activating inert N2molecules. Herein, we report the synthesis of anatase-phase black TiO2–xSynanoplatelets enriched with abundant oxygen vacancies and sulfur anion dopants (VO-S-rich TiO2–xSy) by ion exchange method at gentle conditions. The VO-S-rich TiO2–xSynanoplatelets display a narrowed bandgap of 1.18 eV and much stronger light absorption that extends to the near-infrared (NIR) region. The co-presence of oxygen vacancies and sulfur dopants facilitates the adsorption of N2molecules, promoting the reaction rate of N2photofixation. Theoretical calculations reveal the synergistic effect of oxygen vacancies and sulfur dopants on visible–NIR light adsorption and photoexcited carrier transfer/separation. The VO-S-rich TiO2–xSyexhibits improved ammonia yield rates of 114.1 μmol g–1h–1under full-spectrum irradiation and 86.2 μmol g–1h–1under visible–NIR irradiation, respectively. Notably, even under only NIR irradiation (800–1100 nm), the VO-S-rich TiO2–xSycan still deliver an ammonia yield rate of 14.1 μmol g–1h–1. This study presents the great potential to regulate the activity of photocatalysts by rationally engineering the defect sites and dopant species for room-temperature N2reduction.

Numerous theoretical simulation works have predicted the fantastic properties of arsenene, such as a tunable band gap, topological states, and a high carrier mobility. However, the experimental synthesis of two-dimensional arsenic materials is still difficult. Herein, we report the epitaxial growth of single-crystalline few-layer gray arsenic nanoflakes with hexagonal and half-hexagonal shapes via a van der Waals epitaxy method. The gray arsenic nanoflakes can be transferred from mica to other substrates without structural damage. Moreover, a universal method for estimating the antidegradation efficiency of polymer-passivated gray arsenic nanoflakes by determining the interfacial interaction energies and geometry changes via first-principles calculations was developed. Consistent with theoretical predictions, we further experimentally confirm that functional polymer coating can effectively suppress the chemical degradation and phase transformation of gray arsenic nanoflakes for at least 50 days under ambient exposure, thus facilitating further nanodevice fabrication, preservation, and measurements. Moreover, the gray arsenic nanoflakes show metal to semiconductor transformation after long-term ambient exposure owing to the oxidation of arsenic in air.

With the rising cost and safety concerns associated with lithium-ion batteries (LIBs), multivalent metal-ion batteries (MMIBs) have been considered as promising candidates for energy storage applications, due to their abundant reserves, high theoretical volume capacity, and low cost. However, the development of MMIBs is seriously hampered by the lack of suitable cathode materials that can reversibly accommodate the insertion/extraction of multivalent metal ions. Metal sulfides (MSs) are promising cathode materials for MMIBs owing to the relatively weak electrostatic interaction between their soft lattice anions and highly polarized multivalent metal ions. Unfortunately, the conventional MSs suffer from low diffusion kinetics, poor material efficiency, and large volume expansion, resulting in unsatisfying electrochemical performance. In this review, we first review the challenges faced by MSs in non-aqueous MMIBs and summarize the effective strategies commonly used to improve electrochemical performance. Additionally, the recent progress regarding MSs cathodes in MMIBs is also summarized. Finally, the challenges of MS cathodes used in MMIBs are discussed and the potential future direction is also highlighted. This review is expected to provide guidance for the development of high-performance cathode materials based on MSs for MMIBs.

Aqueous rechargeable magnesium batteries hold immense potential for intrinsically safe, cost-effective, and sustainable energy storage. However, their viability is constrained by a narrow voltage range and suboptimal compatibility between the electrolyte and electrodes. Herein, we introduce an innovative ternary deep eutectic Mg-ion electrolyte composed of MgCl2·6H2O, acetamide, and urea in a precisely balanced 1:1:7 molar ratio. This formulation was optimized by leveraging competitive solvation effects between Mg2+ions and two organic components. The full batteries based on this ternary eutectic electrolyte, Mn-doped sodium vanadate (Mn-NVO) anode, and copper hexacyanoferrate cathode exhibited an elevated voltage plateau and high rate capability and showcased stable cycling performance. Ex-situ characterizations unveiled the Mg2+storage mechanism of Mn-NVO involving initial extraction of Na+followed by subsequent Mg2+intercalation/deintercalation. Detailed spectroscopic analyses illuminated the formation of a pivotal solid-electrolyte interphase on the anode surface. Moreover, the solid-electrolyte interphase demonstrated a dynamic adsorption/desorption behavior, referred to as the “breathing effect”, which substantially mitigated undesired dissolution and side reactions of electrode materials. These findings underscore the crucial role of rational electrolyte design in fostering the development of a favorable solid-electrolyte interphase that can significantly enhance compatibility between electrode materials and electrolytes, thus propelling advancements in aqueous multivalent-ion batteries.

Rechargeable magnesium (Mg) batteries assembled with dendrite-free, safe, and earth-abundant metal Mg anodes potentially have the advantages of high theoretical specific capacity and energy density. Nevertheless, owing to the large polarity of divalent Mg2+ions, the insertion of Mg2+into electrode materials suffers from sluggish kinetics, which seriously limit the performance of Mg batteries. Herein, we demonstrate an atomic substitution strategy for the controlled preparation of ultrathin black TiO2–x(B-TiO2–x) nanoflakes with rich oxygen vacancies (OVs) and porosity by utilizing ultrathin 2D TiS2nanoflakes as precursors. We find out that the presence of OVs in B-TiO2–xelectrode material can greatly improve the electrochemical performances of rechargeable Mg batteries. Both experimental results and density functional theory simulations confirm that the introduction of OVs can remarkably enhance the electrical conductivity and increase the number of active sites for Mg2+ion storage. The vacancy-rich B-TiO2–xnanoflakes exhibit high reversible capacity and good capacity retention after long-term cycling at large current densities. It is hoped that this work can provide valuable insights and inspirations on the defect engineering of electrode materials for rechargeable magnesium batteries.

Electrochemical CO2reduction has been considered as a promising route for renewable energy storage and carbon-neutral energy cycle. However, the selectivity and stability of electrocatalysts for CO2reduction need to be improved. Two-dimensional (2D) layered electrocatalysts with high conductivity and abundant active sites have been considered as good candidates for CO2reduction. Herein, we propose a liquid-exfoliation strategy to prepare ultrathin 2D bismuth (Bi) nanosheets towards efficient electrocatalytic CO2conversion. Compared with bulk Bi, the increased edge sites on ultrathin Bi nanosheets played a vital role in CO2adsorption and reaction kinetics, significantly facilitating CO2-to-formate (HCOOH/HCOO-) conversion. Through density functional theory (DFT) calculation, we found that the *OCOH formation step tended to occur on edge sites rather than on facet sites, as confirmed by the lower Gibbs free energies. Benefited from the high conductivity and rich edge sites, Bi nanosheets exhibited a Faradaic efficiency of 86.0% for formate production and a high current density of 16.5 mA cm−2at − 1.1 V (vs.RHE), much superior to bulk Bi. Moreover, the Bi nanosheets could maintain well-preserved catalytic activity after long-term testing for over consecutive 10 h. We hope this study may provide new insights for the fabrication of novel 2D nanostructured metals for highly-efficient and long-life electrocatalytic CO2conversion.

The catalytic conversion of nitrogen to ammonia is one of the most important processes in nature and chemical industry. However, the traditional Haber-Bosch process of ammonia synthesis consumes substantial energy and emits a large amount of carbon dioxide. Solar-driven nitrogen fixation holds great promise for the reduction of energy consumption and environmental pollution. On the basis of both experimental results and density functional theory calculations, here we report that the oxygen vacancy engineering on ultrathin BiOBr nanosheets can greatly enhance the performance for photocatalytic nitrogen fixation. Through the addition of polymetric surfactant (polyvinylpyrrolidone, PVP) in the synthesis process, VO-BiOBr nanosheets with desirable oxygen vacancies and dominant exposed {001} facets were successfully prepared, which effectively promote the adsorption of inert nitrogen molecules at ambient condition and facilitate the separation of photoexcited electrons and holes. The oxygen defects narrow the bandgap of VO-BiOBr photocatalyst and lower the energy requirement of exciton generation. In the case of the specific surface areas are almost equal, the VO-BiOBr nanosheets display a highly improved photocatalytic ammonia production rate (54.70 μmol·g–1·h–1), which is nearly 10 times higher than that of the BiOBr nanoplates without oxygen vacancies (5.75 μmol·g–1·h–1). The oxygen vacancy engineering on semiconductive nanomaterials provides a promising way for rational design of catalysts to boost the rate of ammonia synthesis under mild conditions.

Rechargeable magnesium ion batteries (RMIBs) have received growing attention due to their advantages of abundant resources, low price, environmental friendliness, and high volumetric capacities. However, the highly polarized Mg2+ions tend to interact with cathode materials, resulting in the sluggish diffusion kinetics. Therefore, design and synthesis high-performance cathode materials are crucial to the development of RMIBs. Most organic cathode materials for RMIBs not only face the problems of poor intrinsic conductivity and low density of the active material, but also are easily soluble in organic electrolytes and have complex redox mechanisms. At present, most of the research on cathodes for RMIBs is inorganic materials. In recent years, researchers have devoted great effort to the design of efficient cathode materials for RMIBs and the reported cathode materials mainly include transition metal oxides, transition metal sulfides, transition metal selenides, polyanionic compounds, and so on. In this review, we provide an extensive overview of different types of inorganic cathodes for RMIBs, with emphasis on describing the structural characteristics, the charge storage mechanisms, electrochemical properties and optimization ideas of different types of cathodes, highlighting some common strategies currently used to improve the electrochemical magnesium storage performance of cathodes. The aim of this widely covered review is to present important research works on different types of inorganic materials when used as cathodes for RMIBs, to summarize the challenges they face and the future directions. This is a departure from articles with an in-depth study of a particular branch. We hope to promote more research efforts on RMIBs in the future.

To produce hydrogen and oxygen from photocatalytic overall splitting of pure water provides a promising green route to directly convert solar energy to clean fuel. However, the design and fabrication of high-efficiency photocatalyst is challenging. Here we present that by connecting different nanostructures together in a rational fashion, components that cannot individually split water into H2and O2can work together as efficient photocatalyst with high solar-to-hydrogen (STH) energy conversion efficiency and avoid the use of any sacrificial reagent. Specifically, Te/SnS2/Ag artificial nanoleaves (ANLs) consist of ultrathin SnS2nanoplates grown on Te nanowires and decorated with numerous Ag nanoparticles. The appropriate band structure of Te/SnS2p-n junctions and the surface plasmon resonance of Ag nanoparticles synergistically enhance the quantum yield and separation efficiency of electron-hole pairs. As a result, Te/SnS2/Ag ANLs enable visible-light driven overall water-splitting without any sacrificial reagent and exhibit high H2and O2production rates of 332.4 and 166.2μmolh−1, respectively. Well-preserved structure after long-term measurement indicates its high stability. It represents a feasible approach for direct H2production from only sunlight, pure water, and rationally-designed ANL photocatalysts.

Rechargeable magnesium batteries (RMBs) show great potential in large-scale energy storage systems, due to Mg2+with high polarity leading to strong interactions within the cathode lattice, and the limited discovery of functional cathode materials with rapid kinetics of Mg2+diffusion and desirable cyclability retards their development. Herein, we innovatively report the confined synthesis of VS2/polyaniline (VS2/PANI) hybrid nanosheets. The VS2/PANI hybrids with expanded interlayer spacing are successfully prepared through the exfoliation of VS2and in situ polymerization between VS2nanosheets and aniline. The intercalated PANI increases the interlayer spacing of VS2from 0.57 to 0.95 nm and improves its electronic conductivity, leading to rapid Mg-ion diffusivity of 10–10–10–12cm2s–1. Besides, the PANI sandwiched between layers of VS2is conducive to maintaining the structural integrity of electrode materials. Benefiting from the above advantages, the VS2/PANI-1 hybrids present remarkable performance for Mg2+storage, showing high reversible discharge capacity (245 mA h g–1at 100 mA g–1) and impressive long lifespan (91 mA h g–1after 2000 cycles at 500 mA g–1). This work provides new perspectives for designing high-performance cathode materials based on layered materials for RMBs.

Rechargeable magnesium batteries (RMBs) are considered as potential energy storage devices due to their high volumetric specific capacity, good safety, as well as source abundance. Despite extensive efforts devoted to constructing an efficient magnesium battery system, the sluggish Mg2+diffusion in conventional cathode materials often leads to slow rate kinetics, low capacity, and poor cycling lifespan. Although transition metal selenides with soft anion frameworks have attracted extensive attention, their Mg2+storage mechanism still needs to be clarified. Herein, we demonstrate that the ultrathin CoSe2nanoribbons can be used as a robust cathode material for RMBs and reveal a novel Mg2+storage mechanism based on cooperative cationic (Co) and anionic (Se) redox processes via systematic ex-situcharacterizations. Compared to other metal selenide cathodes based on conversion reactions of solely metal cations, the cooperative cationic–anionic redox reactions of the CoSe2cathode contribute to obtaining an enhanced specific capacity and boosted electrochemical kinetics. Moreover, on one hand, the ultrathin nanoribbon structure enables effective contact between the electrode material and electrolyte and on the other hand significantly reduces the length and time consumption of Mg2+diffusion, leading to dominated surface-driven capacitance-controlled Mg2+storage behavior and rapid Mg2+storage kinetics. As a result, the ultrathin CoSe2nanoribbon cathode exhibits a reversible discharge capacity of ∼130 mAh g–1at 100 mA g–1, good rate capability (116 mAh g–1at 300 mA g–1), and long cyclability over 600 cycles. This finding confirms the development potentiality of polyvalent metal selenide cathode materials based on a cooperative cationic–anionic redox mechanism for the construction of next-generation multivalent secondary batteries.

Lithium–sulfur batteries are desirable for portable and wearable electronic devices because of their high energy density, low cost and environmental friendliness. Herein, the fabrication of superstretchable Li−S batteries based on highly elastic gel cathodes (fracture strain: 1671%), gel electrolytes (fracture strain: 1223%), zigzag Cu wire-interconnected Li anode pieces and soft packages, is demonstrated. A phase inversion approach is developed to prepare gel cathodes composed of a homogeneously distributed 3D porous fluorinated copolymer skeleton, interlaced electron-conductive networks and sulfur-encapsulated hierarchical polar nanocomposites. The highly elastic gel cathodes possess tri-continuous structures with interpenetrated macropores favourable for high sulfur loading, electrolyte permeation and ion transport. The gel electrolytes with an amorphous phase copolymer matrix and tethered anions exhibit high ionic conductivity, thermal stability, flexibility and effective suppression of Li dendrite growth. The soft-packed Li‒S batteries can be stretched up to 420% of their original length, function normally at 80 °C and deliver an ultrahigh areal capacity of 11.0 mAh cm−2at a sulfur loading of 14 mg cm−2.

Design and fabrication of novel electrode materials with excellent specific capacitance and cycle stability are urgent for advanced energy storage devices, and the combinability of multiple modification methods is still insufficient. Herein, Ni2+, Zn2+double-cation-substitution Co carbonate hydroxide (NiZnCo-CH) nanosheets arrays were established on 3D copper with controllable morphology (3DCu@NiZnCo-CH). The self-standing scalable dendritic copper offers a large surface area and promotes fast electron transport. The 3DCu@NiZnCo-CH electrode shows a markedly improved electrochemical performance with a high specific capacity of ∼1008 C g–1at 1 A g–1(3.2, 2.83, and 1.26 times larger than Co-CH, ZnCo-CH, and NiCo-CH, respectively) and outstanding rate capability (828.8 C g–1at 20 A g–1) due to its compositional and structural advantages. Density functional theory (DFT) calculation results illustrate that cation doping adjusts the adsorption process and optimizes the charge transfer kinetics. Moreover, an aqueous hybrid supercapacitor based on 3DCu@NiZnCo-CH and rGO demonstrates a high energy density of 42.29 Wh kg–1at a power density of 376.37 W kg–1, along with superior cycling performance (retained 86.7% of the initial specific capacitance after 10,000 cycles). Impressively, these optimized 3DCu@NiZnCo-CH//rGO devices with ionic liquid can be operated stably in a large potential range of 4 V with greatly enhanced energy density and power capability (110.12 Wh kg–1at a power density of 71.69 W kg–1). These findings may shed some light on the rational design of transition-metal compounds with tunable architectures by multiple modification methods for efficient energy storage.

The conversion of chemically inert carbon dioxide and its photoreduction to value-added products have attracted enormous attention as an intriguing prospect for utilizing the principal greenhouse gas CO2. Herein, we explore the use of Ag25clusters with well-defined atomic structures for high-selectivity photocatalytic hydrogenation of CO2to methane. Ag25clusters, with molecular-like properties and surface plasmon resonance, exhibit competitive catalytic activity for light-driven CO2reduction that yield an almost 100% product selectivity of methane at a relatively mild temperature (100 °C). DFT calculations reveal that the absorption of CO2on Ag25clusters is energetically favorable. The methanation of the Ag25cluster catalyst has been investigated by operandoinfrared spectroscopy, verifying that methane was produced through a −H-assisted multielectron reaction pathway via the transformation of formyl and formaldehyde species to form surface CHx. This work presents a highly efficient strategy for high-performance CO2methanation via well-defined metal cluster catalysts.