Direct Conversion of Metal Organic Frameworks into Porous Rugby Phosphides by Plasma for Oxygen Evolution.

Electrolytic seawater is a green, sustainable, and promising approach for hydrogen production. Benefiting from the cost-effectiveness, crystal structures, and tailorable modification, transition metal phosphides become a highly attractive catalyst for the electrolysis of water. Considering the sufficient exposure and intrinsic catalytic activity of metal sites, here, carbon layer-coated NiFeP nanocrystals with a porous rugby structure are synthesized by Ar-H2 plasma. Activated PH radical in plasma is the key point to achieve phosphatization at a low temperature. The obtained porous rugby NiFeP catalyst exhibits excellent catalytic activity under alkaline conditions (300 mV in freshwater and 370 mV in seawater, 1000 mA cm-2), good corrosion resistance, and superior operational stability (>100 h). Theoretical calculations prove that Fe introduction and subsequent phosphorization weaken the adsorption of *O and *OH, thus improving the oxygen evolution reaction performance. Plasma phosphorization offers exciting opportunities for the in situ modification of other types of framework materials.

Four new lycoctonine-type C19-diterpenoid alkaloids from the whole plants of Delphinium kamaonense.

Four new lycoctonine-type C19-diterpenoid alkaloids kamaonensines H-K (1-4) have been isolated from the whole plants of Delphinium kamaonense, together with 12 known compounds (5-16). Interestingly, kamaonensines 1-3 contained a rare nitrone (immine N-oxide) moiety, respectively. Their structures were established by spectroscopic analyses. The active evaluation of compounds (1-16) by LPS induced RAW 264.7 macrophages showed that compounds 4 and 8 displayed strong anti-inflammatory activities. While compounds 11 and 12 also showed strong cytotoxicities by the RAW 264.7 cell viability assay.

Zeolitic Imidazolate Framework-Derived Zn/Co-S@Ni(OH)2 Nanoarrays with Excellent Energy Storage and Electrocatalytic Performance.

The design and development of high-performance electrochemical electrode materials are crucial for energy storage and conversion systems. This work reports a facile preparation of a self-supported Zn/Co-S@Ni(OH)2 array electrode in which a Zn/Co-S nanosheet is derived from a leaf-like zeolitic imidazolate framework (Zn/Co-ZIF-L). The core-shell structure provides multiple benefits such as enhanced electrical conductivity, an abundance of exposed active sites, and strong electronic interactions between Zn/Co-S and ultra-thin Ni(OH)2 nanosheets, facilitating faster charge transfer. Consequently, Zn/Co-S@Ni(OH)2 demonstrates remarkable electrochemical characteristics as an electrode material for supercapacitors with an area capacitance of 12.9 F cm-2 at a current density of 2 mA cm-2 in 2 M KOH. The assembled asymmetric supercapacitor device achieves a high energy density of 0.95 mW h cm-2, while showing excellent longevity with a retention of 90.9% over 5000 cycles. Additionally, the Zn/Co-S@Ni(OH)2 arrays demonstrate significant oxygen evolution reaction activity with an overpotential of 242 mV at 10 mA cm-2 in 1 M KOH and significant stability for more than 100 h. This work provides a valuable approach for synthesizing bifunctional electrode materials for both energy storage and electrocatalysis applications.

Electron-Redistributed NiCo@NiFe-LDH Core-Shell Heterostructure for Significantly Enhancing Electrochemical Water Splitting.

Layered double hydroxides (LDHs) are some of the most promising precursors for the development of economically stable and efficient electrocatalysts for water splitting. An effective strategy for designing excellent performance electrocatalysts is to assemble core-shell heterostructures with a tunable electronic structure. In this work, three core-shell heterostructure electrocatalysts (NiCo@NiFe-LDH100/150/200) are developed by a simple hydrothermal and subsequent electrodeposition method on Ni foam. Among them, NiCo@NiFe-LDH150/NF exhibits the best oxygen evolution reaction electrocatalytic activity and long-term stability with a low overpotential of 197 mV to deliver a current density of 10 mA cm-2. In addition, an efficient and stable alkaline electrolytic cell with NiCo@NiFe-LDH150/NF both as the cathode and anode achieves a voltage of 1.66 V at a current density of 10 mA cm-2 and realization of ultralong stability at current densities of 20 and 200 mA cm-2 for 200 h. Density functional theory calculations reveal the strong electron interaction at the heterogeneous interface of the NiCo@NiFe-LDH150/NF core-shell structure, which effectively improves the intrinsic electron conductivity and ion diffusion kinetics and makes an important contribution to the electrocatalytic performance of the material. This work provides a new idea for the selection of materials for electrochemical water splitting by the construction of heterojunction interfaces.

Enhancing cation storage performance of layered double hydroxides by increasing the interlayer distance.

Layered double hydroxides (LDH) can be transformed from alkaline supercapacitor material into metal-cation storage cathode working in neutral electrolytes through electrochemical activation. However, the rate performance for storing large cations is restricted by the small interlayer distance of LDH. Herein, the interlayer distance of NiCo-LDH is expanded by replacing the interlayer nitrate ions with 1,4-benzenedicarboxylic anions (BDC), leading to the enhanced rate performance for storing large cations (Na+, Mg2+, and Zn2+), whereas almost the unchanged one for storing small-radius Li+ ions. The improved rate performance of the BDC-pillared LDH (LDH-BDC) stems from the reduced charge-transfer and Warburg resistances during charge/discharge due to the increased interlayer distance, as revealed by in situ electrochemical impedance spectra. The asymmetric zinc-ion supercapacitor assembled with LDH-BDC and activated carbon presents high energy density and cycling stability. This study demonstrates an effective strategy to improve the large cation storage performance of LDH electrodes by increasing the interlayer distance.

Synthesis, Photophysics and Tunable Reverse Saturable Absorption of Bis-Tridentate Iridium(III) Complexes via Modification on Diimine Ligand.

Five novel bis-tridentate Ir(III) complexes (Ir-1−Ir-5) incorporating versatile N^N^C ligands and a N^C^N ligand (1,3-di(2-pyridyl)-4,6-dimethylbenzene) were synthesized. With the combination of experimental and theoretical methods, their steady and transient state characteristics were researched scientifically. The UV-visible absorption spectra show that the broadband charge transfer absorbance of those bis-tridentate Ir(III) complexes can reach 550 nm, all of these complexes reveal the long-lasting phosphorescent emission. Because the excited-state absorption is more powerful than the ground-state absorption, a sturdy reverse saturable absorption (RSA) process can ensue in the visible and near-infrared regions when the complexes are exposed to a 532 nm laser. Therefore, the optical power limiting (OPL) effect follows the trend: Ir-5 > Ir-4 ≈ Ir-3 > Ir-2 > Ir-1. Generally speaking, the expansion of π-conjugation and the introduction of electron donating/withdrawing groups on the N^N^C ligand could effectively elevate the OPL effect. Therefore, these octahedral bis-tridentate Ir(III) complexes might be exploited as potential OPL materials.

The Composite-Template Method to Construct Hierarchical Carbon Nanocages for Supercapacitors with Ultrahigh Energy and Power Densities.

3D hierarchical carbon nanocages (hCNC) are becoming new platforms for advanced energy storage and conversion due to their unique structural characteristics, especially the combination of multiscale pore structure with high conductivity of sp2 carbon frameworks, which can promote the mass/charge synergetic transfer in various electrochemical processes. Herein, the MgO@ZnO composite-template method is developed to construct hCNC and nitrogen-doped hCNC (hNCNC), which integrates the advantages of the in situ MgO template method and ZnO self-sacrificing template method. The hierarchical MgO template provides the scaffold for depositing carbon nanocages, while the self-sacrificing ZnO template helps create abundant micropores while promoting the graphitization degree, so that the microstructures of the products are effectively regulated. The optimized hCNC and hNCNC have an increased specific surface area and conductivity, which can further boost the mass/charge synergetic transfer. As the electrode materials of supercapacitors, the optimal hCNC(hNCNC) exhibits a high specific capacitance of 281(348) F g-1 in KOH and 276(297) F g-1 in EMIMBF4 electrolytes at 1 A g-1 . The ultrahigh energy and power densities are realized, accompanied by a high-rate capability and long cycling stability. The record-high energy densities of 141.8-71.4 Wh kg-1 are achieved in EMIMBF4 at power densities of 10.0-250.4 kW kg-1 .

Assembly of Metal-Organic Frameworks on Transition Metal Phosphides as Self-Supported Electrodes for High-Performance Hybrid Supercapacitors.

In this work, the composite electrode composed of metal-organic frameworks and transition metal phosphides is first assembled on the nickel foam substrate. The as-prepared NiCo-MOF-74@Ni12P5/NF exhibits excellent performances with ultrahigh specific capacitance (12.8 F/cm2 at 1 mA/cm2), stable charge-discharge rate (82.8%), and excellent cycling stability (reserve 73.90% after 5000 charge and discharge cycles at 30 mA/cm2), which are better than those of NiCo-MOF-74@NF without phosphating treatment of nickel foam. The corresponding hybrid supercapacitor (SC) device (NiCo-MOF-74@Ni12P5/NF//AC) delivers high storage capability (44.33 W·h/kg at 800 W/kg) and distinguished operating durability (83.04% after 5000 cycles). In addition, an all-solid-state hybrid SC successfully lit the LED for more than 2 min, which means that there is viable potential for practical applications in energy storage. The improved electrical properties are mainly due to the 3D heterostructure, the positive cooperative binding of nickel and cobalt elements, and the excellent electrical conductivity of the phosphide. As a result, this study proves the possibility of practical applications of NiCo-MOF-74@Ni12P5/NF electrodes for energy storage in hybrid SCs.

Enhancing the Reduction Kinetics of LiSF6 Batteries by Dispersed Cobalt Phthalocyanines on Porous Carbon.

Reducing SF6 (as gas cathode) in Li batteries is a promising concept for the double benefit of mildly converting greenhouse SF6 and providing a high theoretical energy density of 3922 Wh kg-1 . However, the reduction process is hampered by its sluggish kinetics. Here, cobalt phthalocyanine (CoPc) molecules immobilized on porous carbon matrix are, for the first time, introduced to the LiSF6 chemistry to deliver an enhanced energy density. It is revealed that the high redox potential of Co(II)Pc/[Co(I)Pc]- (≈2.85 V) facilitates the formation of Co(I)N4 sites to catalyze the SF6 electrochemical reduction. By using highly porous holey nitrogen-doped carbon nanocages as carbon matrix, the LiSF6 cells deliver a high discharge voltage of 2.82 V at 50 mA gC+CoPc -1 and an unprecedented areal capacity of 25 mAh cm-2 at 0.1 mA cm-2 , much superior to previous results. This work opens up new possibilities for high-efficiency conversion of SF6 in lithium batteries.

A Naphthalenediimide-Based Metal-Organic Framework and Thin Film Exhibiting Photochromic and Electrochromic Properties.

A multifunctional metal-organic framework, NBU-3, has been explored as a 2D three-connected network based on a naphthalenediimide-based ligand. The NBU-3 crystals display photochromic properties, and NBU-3 thin films on FTO substrates exhibit electrochromic properties. NBU-3 is the first example of MOF materials containing both photochromic and electrochromic properties, which can be desirable for thin film devices.

Simultaneously Improving Energy Storage and Oxygen Evolution Reaction by Causing Regional Defects in MOF-on-MOF Derived Hollow Se-Doped CoP-Fe2P Heterojunctions.

Doping heteroatoms into metal phosphides to modify their electronic structure is an effective method, but the incomplete exposure of active sites is its inherent drawback. In this experiment, both Se doping and P vacancies are simultaneously introduced into CoP-Fe2P (named CoFe-P-Se) to enhance the internal reactivity. Benefiting from the unique hollow porous structure derived from the MOF-on-MOF template, as well as the enhanced intrinsic activity achieved by P defects and Se doping, CoFe-P-Se exhibits a high specific capacitance of 8.41 F cm-2 at a current density of 2 mA cm-2 when used as a supercapacitor electrode. When assembled into a hybrid supercapacitor with activated carbon, the energy density reaches 0.488 mWh cm-2 at a power density of 1.534 mW cm-2, and the capacity retention after 5000 charge-discharge cycles is as high as 90.65%. As an oxygen evolution reaction (OER) electrode, the CoFe-P-Se electrode shows a low overpotential of only 230 mV at a current density of 10 mA cm-2 and 278 mV at 100 mA cm-2. Additionally, it exhibits excellent stability for over 50 h at a current density of 100 mA cm-2. The designed element doping and vacancy engineering in this work will provide an insight for constructing high-performance electrodes.

Design and fabrication of MoO42--intercalated LDH nanosheets coated on Co9S8 nanotubes with enhanced cycling stability for high-performance supercapacitors.

Transition metal sulfides are promising electrode materials for supercapacitors due to their excellent electrochemical performance and high conductivity. Unfortunately, the low rate performance and poor cycling stability limited their progress towards commercial applications. Herein, the core-shell structure of MoO42--intercalated LDHs coated on Co9S8 nanotubes was rationally designed and prepared to improve their electrochemical performance and cycling stability by adjusting the composition of LDHs. Compared to NiMo-LDH@Co9S8 and CoMo-LDH@Co9S8, the optimized NiCoMo-LDH@Co9S8 electrode exhibits excellent areal specific capacitance (11 F cm-2 at 3 mA cm-2) and excellent cycling stability (94.4% after 5000 cycles). In addition, asymmetric supercapacitor devices were assembled with NiCoMo-LDH@Co9S8 and activated carbon (AC), which delivered a high energy density of 0.94 mWh cm-2, at a power density of 1.70 mW cm-2, and good cycling stability (89.4% after 5000 cycles). These results indicate that the introduction of MoO42- can enhance the synergistic effect of multiple metals and the synthesized NiCoMo-LDH@Co9S8 core-shell composite has great potential in the development of high-performance electrode materials for supercapacitors.

Zeolitic Imidazolate Framework-Derived Co3S4@NiFe-LDH Core-Shell Heterostructure as Efficient Bifunctional Electrocatalyst for Water Splitting.

The development of stable and efficient bifunctional electrocatalysts is of utmost importance for overall water splitting. This study introduces Co3S4@NiFe-LDH core-shell heterostructure prepared via an electrodeposition of ultrathin NiFe-LDH nanosheet on zeolitic imidazolium framework-derived Co3S4 nanosheet arrays. The bifunctional Co3S4@NiFe-LDH/NF exhibits impressive catalytic performance and long-term stability for both the OER and HER with low overpotentials of 100 mA cm-2 at 235 mV and 10 mA cm-2 at 95 mV in 1 M KOH, respectively. The assembled cell with Co3S4@NiFe-LDH/NF as both cathode and anode shows voltages of 1.595 and 1.666 V at current densities of 10 and 20 mA cm-2, respectively, as well as ultralong stability over 500 h. DFT calculations expose a robust electron interaction at the heterogeneous interface of the Co3S4@NiFe-LDH/NF core-shell structure. This interaction promotes electron transfer from NiFe-LDH to Co3S4 and reduces the energy barriers for OER intermediates, thereby enhancing electrocatalytic activity. This research contributes novel insights toward the promising materials for electrochemical water splitting through the construction of heterojunction interfaces.

Design and construction of hollow metal sulfide/selenide core-shell heterostructure arrays for hybrid supercapacitor.

Transition metal sulfides and selenides are common electrode materials in supercapacitors. However, the slow redox kinetics and structural collapse during charge-discharge cycles of single-component materials have impeded their electrochemical performance. In this study, hollow Co9S8 nanotubes were synthesized through a rational morphology design approach. Subsequently, NiSe2 or Co0.85Se was electrodeposited onto the Co9S8 nanotubes, yielding two core-shell heterostructure arrays, namely, NiSe2@Co9S8 and Co0.85Se@Co9S8. By fully leveraging the advantages and synergistic effects of these dual-phase heterostructures, the NiSe2@Co9S8 and Co0.85Se@Co9S8 configurations demonstrated outstanding areal capacitances of 12.54 F cm-2 and 9.61 F cm-2, respectively, at 2 mA cm-2. When integrated with activated carbon in hybrid supercapacitors, the NiSe2@Co9S8//AC and Co0.85Se@Co9S8//AC devices exhibited excellent energy storage performance, with energy densities of 0.959 mW h at 1.681 mW and 0.745 mW h at 1.569 mW, respectively. Additionally, these hybrid supercapacitors demonstrated remarkable cycling stability, with capacitance retention of 87.5% and 89.5% after 5000 cycles for NiSe2@Co9S8//AC and Co0.85Se@Co9S8//AC, respectively. This study provides a novel approach to the synthesis of multiphase core-shell heterostructures based on metal sulfides and selenides, opening new avenues for future research.

Regulating the d-band electrons of the Fe-N-C single-atom catalyst for high-efficiency CO2 electroreduction by electron-donating S-doping.

Developing highly efficient electrocatalysts is crucially significant for the application of advanced energy conversion. The Fe-N-C single-atom catalyst is promising for CO2 electroreduction reaction (CO2RR) but suffers from insufficient intrinsic activity and inferior conductivity, which could be addressed by redistributing the electron density via heteroatom doping. Herein, we synthesized S-doped Fe-N-C (Fe-SN-C) as an advanced electrocatalyst for CO2RR using a simple trapping-pyrolysis strategy. Density functional theory calculations and experimental results indicate that S doping increases the d-band electrons and conductivity of Fe-SN-C by electron donating, and thus boosts *CO desorption during the CO2RR process and suppresses the competing hydrogen evolution reaction. Consequently, Fe-SN-C exhibits the maximum CO faradaic efficiency of 93% at -0.5 V and the highest partial current density of 10.1 mA cm-2 at -0.8 V for 2e- CO2RR. This finding provides a feasible and controllable method to achieve advanced electrocatalysts for efficient energy conversion.

Controlled preparation of CoNi2S4 nanorods derived from MOF-74 nanoarrays involving an exchange reaction for high energy density supercapacitors.

Binary transition metal sulfides are considered to be a promising material for supercapacitors, possessing richer electrochemically active sites and superior electrochemical performance. Metal-organic frameworks (MOFs) are often used as self-sacrificing templates in the preparation of metal sulfides. Usually, direct sulfidation of MOFs tends to cause collapse of the morphological structure and blockage of the ion transport channels, so that the morphology of the original MOF template can be well preserved by using pyrolysis followed by S2- ion exchange. In this paper, we first prepared NiCo-MOF-74 on nickel foam by an in situ transformation method from layered double hydroxides (LDHs) through a ligand exchange reaction. Then, CoNi2S4 was synthesized in two steps involving the pyrolysis of NiCo-MOF-74 and a subsequent S2- ion exchange reaction. Compared with direct sulfidation, this synthetic strategy can well maintain the rod-like morphology of MOF-74 arrays and prevent structural collapse. The surface of CoNi2S4 has a fine nanosheet structure, which exposes more active sites and shows a high specific capacitance of 7.50 F cm-2 at 2 mA cm-2 and an excellent Coulomb efficiency (96.32%). In addition, the hybrid supercapacitor assembled with activated carbon shows a high energy density of 0.64 mW h cm-2 at a power density of 1.64 mW cm-2 and a high capacitance retention of 88.39% after 5000 cycles. These results indicate that rod-shaped CoNi2S4 can be controllably prepared from MOF-74 involving an exchange reaction and has promising application in high-performance supercapacitors.

A quaternary heterojunction nanoflower for significantly enhanced electrochemical water splitting.

Designing highly-efficient, cost-effective, and stable electrocatalysts for water splitting is essential to producing green hydrogen. In this work, a nanoflower quaternary heterostructured Ni(NO3)2(OH)4/Ni(OH)2/Ni3S2/NiFe-LDH electrocatalyst is successfully synthesized by two-step hydrothermal reactions. The sulfur in the electrocatalyst induces higher valence state metal atoms as active sites to accelerate the formation of O2. As expected, benefiting from the unique structural features and solid electronic interactions, Ni(NO3)2(OH)4/Ni(OH)2/Ni3S2/NiFe-LDH exhibits remarkable oxygen evolution reaction performance with a low overpotential of 223 mV at a current density of 100 mA cm-2, a slight Tafel slope of 65.4 mV dec-1, and outstanding stability in alkaline media. Attractively, using Ni(NO3)2(OH)4/Ni(OH)2/Ni3S2/NiFe-LDH as both a cathode and an anode, the alkaline electrolyzer delivers a current density of 10 mA cm-2 only at a cell voltage of 1.67 V, accompanied by superior durability. This work provides a facile method for the rational design of high-performance quaternary electrocatalysts.

A general strategy to in situ synthesize hollow metal sulfide/MOF heterostructures for high performance supercapacitors.

Metal-organic frameworks (MOFs) have been extensively applied in supercapacitors. Unfortunately, metal active sites in MOFs are commonly blocked and saturated by organic ligands, leading to insufficient positions available for the electrochemical reaction. To address this issue, we develop a novel strategy to design and prepare a series of hollow metal sulfide/MOF heterostructures, which simultaneously alleviate the large volume expansion, avoid slow kinetics of metal sulfides and expose more electrochemically active sites of the MOF. Consequently, the optimized Co9S8/Co-BDC MOF heterostructure presents outstanding electrochemical performance with a high areal specific capacitance of 15.84 F cm-2 at 2 mA cm-2 and a capacitance retention rate of 87.5% after 5000 charge-discharge cycles. The asymmetric supercapacitors based on the heterostructure deliver a high energy density of 0.87 mW h cm-2 and a power density of 19.84 mW cm-2, as well as long cycling stability. This study provides a new strategy for the rational design and in situ synthesis of metal sulfide/MOF heterostructures for electrochemical applications.

Thermally Conductive AlN-Network Shield for Separators to Achieve Dendrite-Free Plating and Fast Li-Ion Transport toward Durable and High-Rate Lithium-Metal Anodes.

Lithium-metal anodes suffer from inadequate rate and cycling performances for practical application mainly due to the harmful dendrite growth, especially at high currents. Herein a facile construction of the porous and robust network with thermally conductive AlN nanowires onto the commercial polypropylene separator by convenient vacuum filtration is reported. The so-constructed AlN-network shield provides a uniform thermal distribution to realize homogeneous Li deposition, super electrolyte-philic channels to enhance Li-ion transport, and also a physical barrier to resist dendrite piercing as the last fence. Consequently, the symmetric Li|Li cell presents an ultralong lifetime over 8000 h (20 mA cm-2 , 3 mAh cm-2 ) and over 1000 h even at an unprecedented high rate (80 mA cm-2 , 80 mAh cm-2 ), which is far surpassing the corresponding performances reported to date. The corresponding Li|LiFePO4 cell delivers a high specific capacity of 84.3 mAh g-1 at 10 C. This study demonstrates an efficient approach with great application potential toward durable and high-power Li-metal batteries and even beyond.

Characterization of hollow hydroxyapatite/copper microspheres prepared from the reduction of copper-modified hydroxyapatite by glucose.

This study employed a co-precipitation method to synthesize copper-modified hydroxyapatite (HA) powders, where Cu(2+) ions had entered the structure of HA and occupied Ca(1) sites in the columns parallel to the c-axis. Through a hydrothermal treatment, hollow HA/copper (Cu(2)O and/or Cu) microspheres with core-shell structures were prepared in solutions containing glucose, sodium carbonate and sodium citrate. When prolonging the reduction time, Cu(2+) ions dissolved from copper-modified HA were reduced by glucose initially to Cu(+) ions and then to Cu atoms, which would precipitate as copper on the surface of HA. The formation of microspheres with hollow structures was explained by the Kirkendall effect which states that diffusion behaviors of ions were different for HA and copper precipitations. Hybrid HA/copper powders might find their applications in gas sensors, catalysts, electrodes and so on.