Self‐Phosphorization of MOF‐Armored Microbes for Advanced Energy Storage

Utilization of microbes as the carbon source and structural template to fabricate porous carbon has incentivized great interests owing to their diverse micromorphology and intricate intracellular structure, apart from the obvious benefit of “turning waste into wealth.” Challenges remain to preserve the biological structure through the harsh and laborious post‐synthetic treatments, and tailor the functionality as desired. Herein, Escherichia coli is directly coated with metal–organic frameworks (MOFs) through in situ assembly to fabricate N, P co‐doped porous carbon capsules expressing self‐phosphorized metal phosphides. While the MOF coating serves as an armoring layer for facilitating the morphology inheritance from the bio‐templates and provides metal sources for generating extra porosity and electrochemically active sites, the P‐rich phospholipids and N‐rich proteins from the plasma membrane enable carbon matrix doping and further yield metal phosphides. These unique structural and compositional features endow the carbon capsules with great capabilities in suppressing polysulfide shuttling and catalyzing reversible oxygen conversion, ultimately leading to the superb performance of lithium–sulfur batteries and zinc–air batteries. Combining the bio‐templating strategy with hierarchical MOF assembly, this work opens a new avenue for the fabrication of highly porous and functional carbon for advanced energy applications.     

Co9S8 Nanoparticles‐Embedded N/S‐Codoped Carbon Nanofibers Derived from Metal–Organic Framework‐Wrapped CdS Nanowires for Efficient Oxygen Evolution Reaction

Metal–organic frameworks (MOFs) with tunable compositions and morphologies are recognized as efficient self‐sacrificial templates to achieve function‐oriented nanostructured materials. Moreover, it is urgently needed to develop highly efficient noble metal‐free oxygen evolution reaction (OER) electrocatalysts to accelerate the development of overall water splitting green energy conversion systems. Herein, a facile and cost‐efficient strategy to synthesize Co₉S₈ nanoparticles‐embedded N/S‐codoped carbon nanofibers (Co₉S₈/NSCNFs) as highly active OER catalyst is developed. The hybrid precursor of core–shell ZIF‐wrapped CdS nanowires is first prepared and then leads to the formation of uniformly dispersed Co₉S₈/N, S‐codoped carbon nanocomposites through a one‐step calcination reaction. The optimal Co₉S₈/NSCNFs‐850 is demonstrated to possess excellent electrocatalytic performance for OER in 1.0 m KOH solution, affording a low overpotential of 302 mV to reach the current density of 10 mA cm^?2, a small Tafel slope of 54 mV dec^?1, and superior long‐term stability for 1000 cyclic voltammetry cycles. The favorable results raise a concept of exploring more MOF‐based nanohybrids as precursors to induce the synthesis of novel porous nanomaterials as non‐noble‐metal electrocatalysts for sustainable energy conversion.     

Okra‐Like Fe7S8/C@ZnS/N‐C@C with Core–Double‐Shelled Structures as Robust and High‐Rate Sodium Anode

Core–multishelled structures with controlled chemical composition have attracted great interest due to their fascinating electrochemical performance. Herein, a metal–organic framework (MOF)‐on‐MOF self‐templated strategy is used to fabricate okra‐like bimetal sulfide (Fe₇S₈/C@ZnS/N‐C@C) with core–double‐shelled structure, in which Fe₇S₈/C is distributed in the cores, and ZnS is embedded in one of the layers. The MOF‐on‐MOF precursor with an MIL‐53 core, a ZIF‐8 shell, and a resorcinol–formaldehyde (RF) layer (MIL‐53@ZIF‐8@RF) is prepared through a layer‐by‐layer assembly method. After calcination with sulfur powder, the resultant structure has a hierarchical carbon matrix, abundant internal interface, and tiered active material distribution. It provides fast sodium‐ion reaction kinetics, a superior pseudocapacitance contribution, good resistance of volume changes, and stepwise sodiation/desodiation reaction mechanism. As an anode material for sodium‐ion batteries, the electrochemical performance of Fe₇S₈/C@ZnS/N‐C@C is superior to that of Fe₇S₈/C@ZnS/N‐C, Fe₇S₈/C, or ZnS/N‐C. It delivers a high and stable capacity of 364.7 mAh g^?1 at current density of 5.0 A g^?1 with 10 000 cycles, and registers only 0.00135% capacity decay per cycle. This MOF‐on‐MOF self‐templated strategy may provide a method to construct core–multishelled structures with controlled component distributions for the energy conversion and storage.     

Sustainable Synthesis of Co@NC Core Shell Nanostructures from Metal Organic Frameworks via Mechanochemical Coordination Self‐Assembly: An Efficient Electrocatalyst for Oxygen Reduction Reaction

Herein, a new type of cobalt encapsulated nitrogen‐doped carbon (Co@NC) nanostructure employing Zn_xCo_1?x(C₃H₄N₂) metal–organic framework (MOF) as precursor is developed, by a simple, ecofriendly, solvent‐free approach that utilizes a mechanochemical coordination self‐assembly strategy. Possible evolution of Zn_xCo_1?x(C₃H₄N₂) MOF structures and their conversion to Co@NC nanostructures is established from an X‐ray diffraction technique and transmission electron microscopy analysis, which reveal that MOF‐derived Co@NC core–shell nanostructures are well ordered and highly crystalline in nature. Co@NC–MOF core–shell nanostructures show excellent catalytic activity for the oxygen reduction reaction (ORR), with onset potential of 0.97 V and half‐wave potential of 0.88 V versus relative hydrogen electrode in alkaline electrolyte, and excellent durability with zero degradation after 5000 potential cycles; whereas under similar experimental conditions, the commonly utilized Pt/C electrocatalyst degrades. The Co@NC–MOF electrocatalyst also shows excellent tolerance to methanol, unlike the Pt/C electrocatalyst. X‐ray photoelectron spectroscopy (XPS) analysis shows the presence of ORR active pyridinic‐N and graphitic‐N species, along with CoN_x? C_y and Co? N_x ORR active (M–N–C) sites. Enhanced electron transfer kinetics from nitrogen‐doped carbon shell to core Co nanoparticles, the existence of M–N–C active sites, and protective NC shells are responsible for high ORR activity and durability of the Co@NC–MOF electrocatalyst.     

Novel MOF‐Derived Co@N‐C Bifunctional Catalysts for Highly Efficient Zn–Air Batteries and Water Splitting

Metal–organic frameworks (MOFs) and MOF‐derived materials have recently attracted considerable interest as alternatives to noble‐metal electrocatalysts. Herein, the rational design and synthesis of a new class of Co@N‐C materials (C‐MOF‐C2‐T) from a pair of enantiotopic chiral 3D MOFs by pyrolysis at temperature T is reported. The newly developed C‐MOF‐C2‐900 with a unique 3D hierarchical rodlike structure, consisting of homogeneously distributed cobalt nanoparticles encapsulated by partially graphitized N‐doped carbon rings along the rod length, exhibits higher electrocatalytic activities for oxygen reduction and oxygen evolution reactions (ORR and OER) than that of commercial Pt/C and RuO₂, respectively. Primary Zn–air batteries based on C‐MOF‐900 for the oxygen reduction reaction (ORR) operated at a discharge potential of 1.30 V with a specific capacity of 741 mA h g_Zn^–1 under 10 mA cm^–2. Rechargeable Zn–air batteries based on C‐MOF‐C2‐900 as an ORR and OER bifunctional catalyst exhibit initial charge and discharge potentials at 1.81 and 1.28 V (2 mA cm^–2), along with an excellent cycling stability with no increase in polarization even after 120 h – outperform their counterparts based on noble‐metal‐based air electrodes. The resultant rechargeable Zn–air batteries are used to efficiently power electrochemical water‐splitting systems, demonstrating promising potential as integrated green energy systems for practical applications.     

Peptide Nanotube‐Templated Biomineralization of Cu2−xS Nanoparticles for Combination Treatment of Metastatic Tumor

1D peptide nanostructures (i.e., peptide nanotubes, PNTs) exhibit tunable chemo‐physical properties and functions such as improved tissue adhesion, increased cellular uptake, and elongated blood circulation. In this study, the application of PNTs as a desirable 1D template for biomineralization of Cu_2?xS nanoparticles (Cu_2?xS NPs, x = 1–2) is reported. Monodisperse Cu_2?xS NPs are uniformly coated on the peptide nanotubes owing to the specific high binding affinity of Cu ions to the imidazole groups exposed on the surface of nanotubes. The Cu_2?xS NP–coated PNTs are further covalently grafted with an oxaliplatin prodrug (Pt–CuS–PNTs) to construct a versatile nanoplatform for combination cancer therapy. Upon 808 nm laser illumination, the nanoplatform induces significant hyperthermia effect and elicits reactive oxygen species generation through electron transfer and Fenton‐like reaction. It is demonstrated that the versatile nanoplatform dramatically inhibits tumor growth and lung metastasis of melanoma in a B16‐F10 melanoma tumor‐bearing mouse model by combined photo‐ and chemotherapy. This study highlights the ability of PNTs for biomineralization of metal ions and the promising potential of such nanoplatforms for cancer treatment.     

Nitrogen‐Doped Graphene‐Encapsulated Nickel–Copper Alloy Nanoflower for Highly Efficient Electrochemical Hydrogen Evolution Reaction

Development of high‐performance and low‐cost nonprecious metal electrocatalysts is critical for eco‐friendly hydrogen production through electrolysis. Herein, a novel nanoflower‐like electrocatalyst comprising few‐layer nitrogen‐doped graphene‐encapsulated nickel–copper alloy directly on a porous nitrogen‐doped graphic carbon framework (denoted as Ni_x Cu_y @ NG‐NC) is successfully synthesized using a facile and scalable method through calcinating the carbon, copper, and nickel hydroxy carbonate composite under inert atmosphere. The introduction of Cu can effectively modulate the morphologies and hydrogen evolution reaction (HER) performance. Moreover, the calcination temperature is an important factor to tune the thickness of graphene layers of the Ni_x Cu_y @ NG‐NC composites and the associated electrocatalytic performance. Due to the collective effects including unique porous flowered architecture and the synergetic effect between the bimetallic alloy core and graphene shell, the Ni₃Cu₁@ NG‐NC electrocatalyst obtained under optimized conditions exhibits highly efficient and ultrastable activity toward HER in harsh environments, i.e., a low overpotential of 122 mV to achieve a current density of 10 mA cm^?2 with a low Tafel slope of 84.2 mV dec^?1 in alkaline media, and a low overpotential of 95 mV to achieve a current density of 10 mA cm^?2 with a low Tafel slope of 77.1 mV dec^?1 in acidic electrolyte.     

Novel Carbon‐Encapsulated Porous SnO2 Anode for Lithium‐Ion Batteries with Much Improved Cyclic Stability

Porous SnO₂ submicrocubes (SMCs) are synthesized by annealing and HNO₃ etching of CoSn(OH)₆ SMCs. Bare SnO₂ SMCs, as well as bare commercial SnO₂ nanoparticles (NPs), show very high initial discharge capacity when used as anode material for lithium‐ion batteries. However, during the following cycles most of the Li ions previously inserted cannot be extracted, resulting in considerable irreversibility. Porous SnO₂ cubes have been proven to possess better electrochemical performance than the dense nanoparticles. After being encapsulated by carbon shell, the obtained yolk–shell SnO₂ SMCs@C exhibits significantly enhanced reversibility for lithium‐ions storage. The reversibility of the conversion between SnO₂ and Sn, which is largely responsible for the enhanced capacity, has been discussed. The porous SnO₂ SMCs@C shows much increased capacity and cycling stability, demonstrating that the porous SnO₂ core is essential for better lithium‐ion storage performance. The strategy introduced in this paper can be used as a versatile way to fabrication of various metal‐oxide‐based composites.     

Water‐Stable Chemical‐Protective Textiles via Euhedral Surface‐Oriented 2D Cu–TCPP Metal‐Organic Frameworks

Abatement of chemical hazards using adsorptive metal‐organic frameworks (MOFs) attracts substantial attention, but material stability and crystal integration into functional systems remain key challenges. Herein, water‐stable, polymer fiber surface–oriented M–TCPP [M = Cu, Zn, and Co; H₂TCPP = 5,10,15,20‐tetrakis(4‐carboxyphenyl)porphyrin] 2D MOF crystals are fabricated using a facile hydroxy double salt (HDS) solid‐source conversion strategy. For the first time, Cu–TCPP is formed from a solid source and confirmed to be highly adsorptive for NH₃ and 2‐chloroethyl ethyl sulfide (CEES), a blistering agent simulant, in humid (80% relative humidity (RH)) conditions. Moreover, the solid HDS source is found as a unique new approach to control MOF thin‐film crystal orientation, thereby facilitating radially arranged MOF crystals on fibers. On a per unit mass of MOF basis in humid conditions, the MOF/fiber composite enhances NH₃ adsorptive capacity by a factor of 3 compared to conventionally prepared MOF powders. The synthesis route extends to other MOF/fiber composite systems, therefore providing a new route for chemically protective materials.     

A Monodispersed Spherical Zr‐Based Metal–Organic Framework Catalyst,Pt/Au@Pd@UIO‐66, Comprising an Au@Pd Core–Shell Encapsulated in a UIO‐66 Center and Its Highly Selective CO2 Hydrogenation to Produce CO

A Zr‐based metal–organic framework (MOF) catalyst, Pt/Au@Pd@UIO‐66, is assembled, where UIO‐66 is Zr₆O₄(OH)₄(BDC)₆ (BDC = 1,4‐benzenedicarboxylate). The gold nanoparticles (NPs) act as the core for the epitaxial growth of Pd shells, and the core–shell monodispersed nanosphere Au@Pd is encapsulated into UIO‐66 to control its morphology and impart nanoparticle functionality. The microporous nature of UIO‐66 assists the adsorption of Pt NPs, which in turn enhances the interaction between NPs and UIO‐66, favoring the formation of isolated and well‐dispersed Pt NP active sites. This MOF exhibits high catalytic activity and CO product selectivity for the reverse‐water–gas‐shift reaction in a fixed‐bed flow reactor.     

Mesoporous Hollow Sb/ZnS@C Core–Shell Heterostructures as Anodes for High‐Performance Sodium‐Ion Batteries

Combining the advantage of metal, metal sulfide, and carbon, mesoporous hollow core–shell Sb/ZnS@C hybrid heterostructures composed of Sb/ZnS inner core and carbon outer shell are rationally designed based on a robust template of ZnS nanosphere, as anodes for high‐performance sodium‐ion batteries (SIBs). A partial cation exchange reaction based on the solubility difference between Sb₂S₃ and ZnS can transform mesoporous ZnS to Sb₂S₃/ZnS heterostructure. To get a stable structure, a thin contiguous resorcinol‐formaldehyde (RF) layer is introduced on the surface of Sb₂S₃/ZnS heterostructure. The effectively protective carbon layer from RF can be designed as the reducing agent to convert Sb₂S₃ to metallic Sb to obtain core–shell Sb/ZnS@C hybrid heterostructures. Simultaneously, the carbon outer shell is beneficial to the charge transfer kinetics, and can maintain the structure stability during the repeated sodiation/desodiation process. Owing to its unique stable architecture and synergistic effects between the components, the core–shell porous Sb/ZnS@C hybrid heterostructure SIB anode shows a high reversible capacity, good rate capability, and excellent cycling stability by turning the optimized voltage range. This novel strategy to prepare carbon‐layer‐protected metal/metal sulfide core–shell heterostructure can be further extended to design other novel nanostructured systems for high‐performance energy storage devices.     

Mineral‐Templated 3D Graphene Architectures for Energy‐Efficient Electrodes

3D graphene networks have shown extraordinary promise for high‐performance electrochemical devices. Herein, the chemical vapor deposition synthesis of a highly porous 3D graphene foam (3D‐GF) using naturally abundant calcined Iceland crystal as the template is reported. Intriguingly, the Iceland crystal transforms to CaO monolith with evenly distributed micro/meso/macropores through the releasing of CO₂ at high temperature. Meanwhile, the hierarchical structure of the calcined template could be easily tuned under different calcination conditions. By precisely inheriting fine structure from the templates, the as‐prepared 3D‐GF possesses a tunable hierarchical porosity and low density. Thus, the hierarchical pores offer space for guest hybridization and provide an efficient pathway for ion/charge transport in typical energy conversion/storage systems. The 3D‐GF skeleton electrode hybridized with Ni(OH)₂/Co(OH)₂ through an optimal electrodeposition condition exhibits a high specific capacitance of 2922.2 F g⁻¹ at a scan rate of 10 mV s⁻¹, and 2138.4 F g⁻¹ at a discharge current density of 3.1 A g⁻¹. The hybrid 3D‐GF symmetry supercapacitor shows a high energy density of 83.0 Wh kg⁻¹ at a power density of 1011.3 W kg⁻¹ and 31.4 Wh kg⁻¹ at a high power density of 18 845.2 W kg⁻¹. The facile fabrication process enables the mass production of hierarchical porous 3D‐GF for high‐performance supercapacitors.     

Improving Polysulfides Adsorption and Redox Kinetics by the Co4N Nanoparticle/N‐Doped Carbon Composites for Lithium‐Sulfur Batteries

Improved conductivity and suppressed dissolution of lithium polysulfides is highly desirable for high‐performance lithium‐sulfur (Li‐S) batteries. Herein, by a facile solvent method followed by nitridation with NH₃, a 2D nitrogen‐doped carbon structure is designed with homogeneously embedded Co₄N nanoparticles derived from metal organic framework (MOF), grown on the carbon cloth (MOF‐Co₄N). Experimental results and theoretical simulations reveal that Co₄N nanoparticles act as strong chemical adsorption hosts and catalysts that not only improve the cycling performance of Li‐S batteries via chemical bonding to trap polysulfides but also improve the rate performance through accelerating the conversion reactions by decreasing the polarization of the electrode. In addition, the high conductive nitrogen‐doped carbon matrix ensures fast charge transfer, while the 2D structure offers increased pathways to facilitate ion diffusion. Under the current density of 0.1C, 0.5C, and 3C, MOF‐Co₄N delivers reversible specific capacities of 1425, 1049, and 729 mAh g^?1, respectively, and retains 82.5% capacity after 400 cycles at 1C, as compared to the sample without Co₄N (MOF‐C) values of 61.3% (200 cycles). The improved cell performance corroborates the validity of the multifunctional design of MOF‐Co₄N, which is expected to be a potentially promising cathode host for Li‐S batteries.     

Co@Co3O4@PPD Core@bishell Nanoparticle‐Based Composite as an Efficient Electrocatalyst for Oxygen Reduction Reaction

Durable electrocatalysts with high catalytic activity toward oxygen reduction reaction (ORR) are crucial to high‐performance primary zinc‐air batteries (ZnABs) and direct methanol fuel cells (DMFCs). An efficient composite electrocatalyst, Co@Co₃O₄ core@shell nanoparticles (NPs) embedded in pyrolyzed polydopamine (PPD) is reported, i.e., in Co@Co₃O₄@PPD core@bishell structure, obtained via a three‐step sequential process involving hydrothermal synthesis, high temperature calcination under nitrogen atmosphere, and gentle heating in air. With Co@Co₃O₄ NPs encapsulated by ultrathin highly graphitized N‐doped carbon, the catalyst exhibits excellent stability in aqueous alkaline solution over extended period and good tolerance to methanol crossover effect. The integration of N‐doped graphitic carbon outer shell and ultrathin nanocrystalline Co₃O₄ inner shell enable high ORR activity of the core@bishell NPs, as evidenced by ZnABs using catalyst of Co@Co₃O₄@PPD in air‐cathode which delivers a stable voltage profile over 40 h at a discharge current density of as high as 20 mA cm^?2.     

Ultrafine Co3O4 Nanoparticles within Nitrogen‐Doped Carbon Matrix Derived from Metal–Organic Complex for Boosting Lithium Storage and Oxygen Evolution Reaction

Transition metal oxides have recently received great attention for application in advanced lithium‐ion batteries (LIBs) and oxygen evolution reaction (OER). Herein, the ethylenediaminetetraacetic cobalt complex as a precursor to synthesize ultrafine Co₃O₄ nanoparticles encapsulated into a nitrogen‐doped carbon matrix (NC) composites is presented. The as‐prepared Co₃O₄/NC‐350 obtained by pyrolysis at 350 °C demonstrates superior rate performance (372 mAh g^?1 at 5.0 A g^?1) and high cycling stability (92% capacity retention after 300 cycles at 1.0 A g^?1) as anode for LIBs. When evaluated as an electrocatalyst for OER, the Co₃O₄/NC‐350 achieves an overpotential of 298 mV at a current density of 10 mA cm^?2. The NC‐encapsualted porous hierarchical structure assures fast and continuous electron transportation, high activity sites, and strong structural integrity. This works offers novel complex precursors for synthesizing transition metal–based electrodes for boosting electrochemical energy conversion and storage.     

WO3 Nanofiber‐Based Biomarker Detectors Enabled by Protein‐Encapsulated Catalyst Self‐Assembled on Polystyrene Colloid Templates

A novel catalyst functionalization method, based on protein‐encapsulated metallic nanoparticles (NPs) and their self‐assembly on polystyrene (PS) colloid templates, is used to form catalyst‐loaded porous WO₃ nanofibers (NFs). The metallic NPs, composed of Au, Pd, or Pt, are encapsulated within a protein cage, i.e., apoferritin, to form unagglomerated monodispersed particles with diameters of less than 5 nm. The catalytic NPs maintain their nanoscale size, even following high‐temperature heat‐treatment during synthesis, which is attributed to the discrete self‐assembly of NPs on PS colloid templates. In addition, the PS templates generate open pores on the electrospun WO₃ NFs, facilitating gas molecule transport into the sensing layers and promoting active surface reactions. As a result, the Au and Pd NP‐loaded porous WO₃ NFs show superior sensitivity toward hydrogen sulfide, as evidenced by responses (R_air/R_gas) of 11.1 and 43.5 at 350 °C, respectively. These responses represent 1.8‐ and 7.1‐fold improvements compared to that of dense WO₃ NFs (R_air/R_gas = 6.1). Moreover, Pt NP‐loaded porous WO₃ NFs exhibit high acetone sensitivity with response of 28.9. These results demonstrate a novel catalyst loading method, in which small NPs are well‐dispersed within the pores of WO₃ NFs, that is applicable to high sensitivity breath sensors.     

Selective Formation of Carbon‐Coated,Metastable Amorphous ZnSnO3 Nanocubes Containing Mesopores for Use as High‐Capacity Lithium‐Ion Battery

Mesoporous and amorphous ZnSnO₃ nanocubes of ～37 nm size coated with a thin porous carbon layer have been prepared using monodisperse ZnSn(OH)₆ as the active precursor and low‐temperature synthesized polydopamine as the carbon precursor. The small single nanocubes cross‐link with each other to form a continuous conductive framework and interconnected porous channels with macropores of 74 nm width. Because of its multi‐featured nanostructure, this material exhibits greatly enhanced integration of reversible alloying/de‐alloying (i.e., transformation of Li_4.4Sn and LiZn to Sn and Zn) and conversion (i.e., oxidation of Sn and Zn to ZnSnO₃) reaction processes with an extremely high capacity of 1060 mA h g^?1 for up to 100 cycles. A high reversible capacity of 650 and 380 mA h g^?1 can also be delivered at rates of 2 and 3 A g^?1, respectively. This excellent electrochemical performance is attributed to the small particle size, well‐developed mesoporosity, the amorphous nature of the ZnSnO₃ and the continuous conductive framework produced by the interconnected carbon layers.     

From UV to Near‐Infrared Light‐Responsive Metal–Organic Framework Composites: Plasmon and Upconversion Enhanced Photocatalysis

The exploitation of photocatalysts that harvest solar spectrum as broad as possible remains a high‐priority target yet grand challenge. In this work, for the first time, metal–organic framework (MOF) composites are rationally fabricated to achieve broadband spectral response from UV to near‐infrared (NIR) region. In the core–shell structured upconversion nanoparticles (UCNPs)‐Pt@MOF/Au composites, the MOF is responsive to UV and a bit visible light, the plasmonic Au nanoparticles (NPs) accept visible light, whereas the UCNPs absorb NIR light to emit UV and visible light that are harvested by the MOF and Au once again. Moreover, the MOF not only facilitates the generation of “bare and clean” Au NPs on its surface and realizes the spatial separation for the Au and Pt NPs, but also provides necessary access for catalytic substrates/products to Pt active sites. As a result, the optimized composite exhibits excellent photocatalytic hydrogen production activity (280 µmol g^?1 h^?1) under simulated solar light, and the involved mechanism of photocatalytic H₂ production under UV, visible, and NIR irradiation is elucidated. Reportedly, this is an extremely rare study on photocatalytic H₂ production by light harvesting in all UV, visible, and NIR regions.     

Exposing {001} Crystal Plane on Hexagonal Ni‐MOF with Surface‐Grown Cross‐Linked Mesh‐Structures for Electrochemical Energy Storage

Hexagonal nickel‐organic framework (Ni‐MOF) [Ni(NO₃)₂·6H₂O, 1,3,5‐benzenetricarboxylic acid, 4‐4′‐bipyridine] is fabricated through a one‐step solvothermal method. The {001} crystal plane is exposed to the largest hexagonal surface, which is an ideal structure for electron transport and ion diffusion. Compared with the surrounding rectangular crystal surface, the ion diffusion length through the {001} crystal plane is the shortest. In addition, the cross‐linked porous mesh structures growing on the {001} crystal plane strengthen the mixing with conductive carbon, inducing preferable conductivity, as well as increasing the area of ion contact and the number of active sites. These advantages enable the hexagonal Ni‐MOF to exhibit excellent electrochemical performance as supercapacitor electrode materials. In a three‐electrode cell, specific capacitance of hexagonal Ni‐MOF in the 3.0 m KOH electrolyte is 977.04 F g^?1 and remains at the initial value of 92.34% after 5,000 cycles. When the hexagonal Ni‐MOF and activated carbon are assembled into aqueous devices, the electrochemical performance remains effective.     

A Dual‐Function Na2SO4 Template Directed Formation of Cathode Materials with a High Content of Sulfur Nanodots for Lithium–Sulfur Batteries

The sulfur content in carbon–sulfur hybrid using the melt‐diffusion method is normally lower than 70 wt%, which greatly decreases the energy density of the cathode in lithium–sulfur (Li‐S) batteries. Here, a scalable method inspired by the commercialized production of Na₂S is used to prepare a hierarchical porous carbon–sulfur hybrid (denoted HPC‐S) with high sulfur content (≈85 wt%). The HPC‐S is characterized by the structure of sulfur nanodots naturally embedded in a 3D carbon network. The strategy uses Na₂SO₄ as the starting material, which serves not only as the sulfur precursor but also as a salt template for the formation of the 3D carbon network. The HPC‐S cathode with such a high sulfur content shows excellent rate performance and cycling stability in Li–S batteries because of the sulfur nanoparticles, the unique carbon framework, and the strong interaction between them. The production method can also be readily scaled up and used in practical Li–S battery applications.